The type of culture medium and the duration of in vitro culture do not influence birthweight of ART singletons

Untangling the independent effect of endometriosis, adenomyosis, and ART-related factors on maternal, placental, fetal, and neonatal adverse outcomes: results from a systematic review and meta-analysis

BACKGROUND

Women with endometriosis may constitute a group at a particularly increased risk of pregnancy-related complications. Furthermore, women selected for assisted reproductive technology (ART) are exposed to additional endocrinological and embryological factors that have been associated with adverse pregnancy outcomes.

OBJECTIVE AND RATIONALE

This study aimed to investigate the independent effect of endometriosis, adenomyosis, and various ART-related factors on adverse maternal, placental, fetal, and neonatal outcomes.

SEARCH METHODS

Published randomized controlled trials, cohort studies, and case-control studies were considered eligible. PubMed, MEDLINE, ClinicalTrials.gov, Embase, and Scopus were systematically searched up to 1 March 2024. This systematic review and meta-analysis was performed in line with the PRISMA and the MOOSE reporting guidelines. To thoroughly investigate the association between endometriosis/adenomyosis and adverse pregnancy outcomes, sub-analyses were conducted, whenever possible, according to: the method of conception (i.e. ART and non-ART conception), the endometriosis stage/phenotype, the coexistence of endometriosis and adenomyosis, any pre-pregnancy surgical treatment of endometriosis, and the form of adenomyosis. The odds ratio (OR) with 95% CI was used as effect measure. The quality of evidence was assessed using the GRADE approach.

OUTCOMES

We showed a higher risk of placenta previa in women with endometriosis compared to controls (34 studies, OR 2.84; 95% CI: 2.47, 3.26; I2 = 83%, moderate quality). The association was observed regardless of the method of conception and was particularly strong in the most severe forms of endometriosis (i.e. rASRM stage III-IV endometriosis and deep endometriosis (DE)) (OR 6.61; 95% CI: 2.08, 20.98; I2 = 66% and OR 14.54; 95% CI: 3.67, 57.67; I2 = 54%, respectively). We also showed an association, regardless of the method of conception, between endometriosis and: (i) preterm birth (PTB) (43 studies, OR 1.43; 95% CI: 1.32, 1.56; I2 = 89%, low quality) and (ii) cesarean section (29 studies, OR 1.52; 95% CI: 1.41, 1.63; I2 = 93%, low quality). The most severe forms of endometriosis were strongly associated with PTB. Two outcomes were associated with adenomyosis both in the main analysis and in the sub-analysis that included only ART pregnancies: (i) miscarriage (14 studies, OR 1.83; 95% CI: 1.53, 2.18; I2 = 72%, low quality) and (ii) pre-eclampsia (7 studies, OR 1.70; 95% CI: 1.16, 2.48; I2 = 77%, low quality). Regarding ART-related factors, the following associations were observed in the main analysis and confirmed in all sub-analyses conducted by pooling only risk estimates adjusted for covariates: (i) blastocyst stage embryo transfer (ET) and monozygotic twinning (28 studies, OR 2.05; 95% CI, 1.72, 2.45; I2 = 72%, low quality), (ii) frozen embryo transfer (FET) and (reduced risk of) small for gestational age (21 studies, OR 0.59; 95% CI, 0.57, 0.61; P < 0.00001; I2 = 17%, very low quality) and (increased risk of) large for gestational age (16 studies, OR 1.70; 95% CI, 1.60, 1.80; P < 0.00001; I2 = 55%, very low quality), (iii) artificial cycle (AC)-FET and pre-eclampsia (12 studies, OR 2.14; 95% CI: 1.91-2.39; I2 = 9%, low quality), PTB (21 studies, OR 1.24; 95% CI 1.15, 1.34; P < 0.0001; I2 = 50%, low quality), cesarean section (15 studies, OR 1.59; 95% CI 1.49, 1.70; P < 0.00001; I2 = 67%, very low quality) and post-partum hemorrhage (6 studies, OR 2.43; 95% CI 2.11, 2.81; P < 0.00001; I2 = 15%, very low quality).

WIDER IMPLICATIONS

Severe endometriosis (i.e. rASRM stage III-IV endometriosis, DE) constitutes a considerable risk factor for placenta previa and PTB. Herein, we recommend against superimposing on this condition other exposure factors that have a strong association with the same obstetric adverse outcome or with different outcomes which, if coexisting, could determine the onset of an ominous obstetric syndrome. Specifically, we strongly discourage the use of AC regimens for FET in ovulatory women with rASRM stage III-IV endometriosis or DE. We also recommend single ET at the blastocyst stage in this high-risk population.

REGISTRATION NUMBER

CRD42023401428.

Is large for gestational age in singletons born after frozen embryo transfer associated with freezing technique or endometrial preparation protocol? A longitudinal national French study

STUDY QUESTION

Is large for gestational age (LGA) observed in babies born after frozen embryo transfer (FET) associated with either the freezing technique or the endometrial preparation protocol?

SUMMARY ANSWER

Artificial cycles are associated with a higher risk of LGA, with no difference in rate between the two freezing techniques (vitrification versus slow freezing) or embryo stage (cleaved embryo versus blastocyst).

WHAT IS KNOWN ALREADY

Several studies have compared neonatal outcomes after fresh embryo transfer (ET) and FET and shown that FET is associated with improved neonatal outcomes, including reduced risks of preterm birth, low birthweight, and small for gestational age (SGA), when compared with fresh ET. However, these studies also revealed an increased risk of LGA after FET. The underlying pathophysiology of this increased risk remains unclear; parental infertility, laboratory procedures (including embryo culture conditions and freezing-thawing processes), and endometrial preparation treatments might be involved.

STUDY DESIGN, SIZE, DURATION

A multicentre epidemiological data study was performed through a retrospective analysis of the standardized individual clinical records of the French national register of IVF from 2014 to 2018, including single deliveries resulting from fresh ET or FET that were prospectively collected in fertility centres. Complementary data were collected from the participating fertility centres and included the vitrification media and devices, and the endometrial preparation protocols.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data were collected from 35 French ART centres, leading to the inclusion of a total of 72 789 fresh ET, 10 602 slow-freezing FET, and 39 062 vitrification FET. Main clinical outcomes were presented according to origin of the transferred embryos (fresh, slow frozen, or vitrified embryos) and endometrial preparations for FET (ovulatory or artificial cycles), comparing five different groups (fresh, slow freezing-ovulatory cycle, slow freezing-artificial cycle, vitrification-ovulatory cycle, and vitrification-artificial cycle). Foetal growth disorders were defined in live-born singletons according to gestational age and sex-specific weight percentile distribution: SGA and LGA if <10th and ≥90th percentiles, respectively. Analyses were performed using linear mixed models with the ART centres as random effect.

MAIN RESULTS AND THE ROLE OF CHANCE

Transfers led to, respectively, 19 006, 1798, and 9195 deliveries corresponding to delivery rates per transfer of 26.1%, 17.0%, and 23.5% after fresh ET, slow-freezing FET, and vitrification FET, respectively. FET cycles were performed in either ovulatory cycles (n = 21 704) or artificial cycles (n = 34 237), leading to 5910 and 10 322 pregnancies, respectively, and corresponding to pregnancy rates per transfer of 31.6% and 33.3%. A significantly higher rate of spontaneous miscarriage was observed in artificial cycles when compared with ovulatory cycles (33.3% versus 21.4%, P < 0.001, in slow freezing groups and 31.6% versus 21.8%, P < 0.001 in vitrification groups). Consequently, a lower delivery rate per transfer was observed in artificial cycles compared with ovulatory cycles both in slow freezing and vitrification groups (15.5% versus 18.9%, P < 0.001 and 22.8% versus 24.9%, P < 0.001, respectively). Among a total of 26 585 live-born singletons, 16 413 babies were born from fresh ET, 1644 from slow-freezing FET, and 8528 from vitrification FET. Birthweight was significantly higher in the FET groups than in the fresh ET group, with no difference between the two freezing techniques. Likewise, LGA rates were higher and SGA rates were lower in the FET groups compared with the fresh ET group whatever the method used for embryo freezing. In a multivariable analysis, the risk of LGA following FET was significantly increased in artificial compared with ovulatory cycles. In contrast, the risk of LGA was not associated with either the freezing procedure (vitrification versus slow freezing) or the embryo stage (cleaved embryo versus blastocyst) at freezing. Regarding the vitrification method, the risk of LGA was not associated with either the vitrification medium used or the embryo stage.

LIMITATIONS, REASONS FOR CAUTION

No data were available on maternal context, such as parity, BMI, infertility cause, or maternal comorbidities, in the French national database. In particular, we cannot exclude that the increased risk of LGA observed following FET with artificial cycles may, at least partially, be associated with a confounding effect of some maternal factors. No information about embryo culture and incubation conditions was available. Most of the vitrification techniques were performed using the same device and with two main vitrification media, limiting the validity of a comparison of risk for LGA according to the device or vitrification media used.

WIDER IMPLICATIONS OF THE FINDINGS

Our results seem reassuring, since no potential foetal growth disorders following embryo vitrification in comparison with slow freezing were observed. Even if other factors are involved, the endometrial preparation treatment seems to have the greatest impact on LGA risk following FET. FET during ovulatory cycles could minimize the risk for foetal growth disorders.

STUDY FUNDING/COMPETING INTEREST(S)

This work has received funding from the French Biomedicine Agency (Grant number: 19AMP002). None of the authors has any conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

The effect of an extended culture period on birth weight among singletons born after single or double vitrified embryo transfer

Aim

To evaluate the effect of an extended culture period on birth weight among singletons born after vitrified-warmed embryo transfer.

Methods

A retrospective cohort study was performed among 12400 women who gave birth to 1015, 1027, 687, and 9671 singletons after single blastocyst transfer, single cleavage-stage embryo transfer, double blastocyst transfer, and double cleavage-stage embryo transfer, respectively.

Results

The unadjusted birth weight of singletons born after vitrified blastocyst transfer were heavier than those born after cleavage-stage transfer (β=30.28, SE=13.17, P=0.022), as were the adjusted birth weights (β=0.09, SE=0.03, P=0.007). In addition, there was a 37% increased odd of having an infant with high birth weight after vitrified blastocyst transfer compared with vitrified cleavage stage transfer (OR=1.37, 95% CI:1.07-1.77).

Conclusion

The unadjusted and adjusted birth weight and odds of having an infant with high birth weight significantly increased after blastocyst transfer compared with cleavage-stage embryo transfer in vitrified-warmed cycles.

Do IVF culture conditions have an impact on neonatal outcomes? A systematic review and meta-analysis

PURPOSE

Are embryo culture conditions, including type of incubator, oxygen tension, and culture media, associated with obstetric or neonatal complications following in vitro fertilization (IVF)?

METHODS

A systematic search of MEDLINE, EMBASE, and Cochrane Library was performed from January 01, 2008, until October 31, 2021. The studies reporting quantitative data on at least one of the primary outcomes (birthweight and preterm birth) for the exposure group and the control group were included. For oxygen tension, independent meta-analysis was performed using Review Manager, comparing hypoxia/normoxia. For culture media, a network meta-analysis was carried out using R software, allowing the inclusion of articles comparing two or more culture media.

RESULTS

After reviewing 182 records, 39 full-text articles were assessed for eligibility. A total of 28 studies were kept for review. Meta-analysis about the impact of incubator type on perinatal outcomes could not be carried out because of a limited number of studies. For oxygen tension, three studies were included. The pairwise meta-analysis comparing hypoxia/normoxia did not show any statistical difference for birthweight and gestational age at birth. For culture media, 18 studies were included. The network meta-analysis failed to reveal any significant impact of different culture media on birthweight or preterm birth.

CONCLUSION

No difference was observed for neonatal outcomes according to the embryo culture conditions evaluated in this review. Further research is needed about the safety of IVF culture conditions as far as future children's health is concerned.

Obstetric and perinatal outcomes after embryos cultured in one-step versus sequential culture media systems in vitrified-warmed single blastocyst transfer cycles

RESEARCH QUESTION

Does type of culture medium used influence obstetric and perinatal outcomes after vitrified-warmed single blastocyst transfers?

DESIGN

Retrospective cohort study involving singletons after vitrified-warmed single blastocyst embryo transfers, using embryos cultured in either Irvine Continuous Single Culture medium (CSC) or Vitrolife G5TM PLUS medium culture system between 2013 and 2020.

RESULTS

A total of 2475 women who had singleton deliveries were included for final analysis: 1478 had embryos cultured in CSC and 997 had embryos cultured in G5TM PLUS medium. Birth outcomes, including preterm birth, mean birth weight, gestational age- and sex-adjusted birth weight (Z-scores), rates of large-for-gestational-age, small-for-gestational-age, low birth weight and macrosomia, and the distribution of newborn gender did not differ significantly between groups in crude and adjusted analyses. Women whose embryos were cultured in G5TM PLUS frequently suffered from pregnancy-induced hypertensive disorders compared with those who had embryos cultured in CSC (4.7% versus 3.0%; P = 0.031). This difference was no longer significant after adjusting for several key confounders (adjusted odds ratio 1.49, 95% CI 0.94 to 2.38, P = 0.087). Other obstetric complications, including gestational diabetes mellitus, preterm premature rupture of membranes, abnormal placentation, postpartum haemorrhage and the mode of delivery were all similar between the two groups.

CONCLUSIONS

The present study adds new information to the current evidence by suggesting that the embryo culture medium does not affect birth outcomes and obstetric complications when comparison is limited to Irvine CSC and Vitrolife G5TM PLUS in vitrified-warmed single blastocyst transfer cycles.

Congenital anomaly and perinatal outcome following blastocyst- vs cleavage-stage embryo transfer: systematic review and network meta-analysis

OBJECTIVES

To compare the reported rate of any congenital anomaly and perinatal outcome of pregnancy following blastocyst- vs cleavage-stage embryo transfer using a pairwise meta-analysis and to evaluate the same outcomes following fresh-blastocyst, frozen-blastocyst, fresh-cleavage or frozen-cleavage embryo transfer using a network meta-analysis.

METHODS

A literature search was performed in PubMed, Scopus and CENTRAL and registers for ongoing studies, from inception to February 2022, for randomized controlled trials (RCTs) with any sample size and observational studies including at least 100 live births per group, comparing the rates of any congenital anomaly and perinatal outcome of pregnancy following fresh/frozen embryo transfer at cleavage (day 2-3) vs blastocyst (day 5-7) stage. Risk ratios (RRs) along with their 95% CIs were pooled via a random-effects model meta-analysis. Within a frequentist network meta-analysis framework, outcomes of all four treatment modalities (i.e. fresh-blastocyst, fresh-cleavage, frozen-blastocyst, frozen-cleavage) were compared further. Any congenital anomaly constituted the primary outcome, whereas preterm delivery (delivery < 37 weeks), low birth weight (LBW; < 2500 g), gender of the neonate (male), perinatal death and healthy neonate (defined as liveborn neonate, delivered at term, weighing ≥ 2500 g, surviving for at least 28 days postbirth and without any congenital anomaly) were considered as secondary outcomes. Subgroup analyses by plurality (liveborn singleton vs multiple pregnancy) were conducted in the pairwise and network meta-analyses. The risk of bias was assessed using the RoB2 tool for RCTs and the ROBINS-I tool for non-randomized studies. Certainty of evidence was assessed using GRADE.

RESULTS

Through the literature search, 550 studies were retrieved and 33 were included in the systematic review. We found no significant difference in the risk for any congenital anomaly between blastocyst- and cleavage-stage transfer (RR, 0.80 (95% CI, 0.63-1.03); 10 studies; n = 192 442; I²  = 85.5%). An increased probability of a male neonate was observed following blastocyst- vs cleavage-stage transfer (RR, 1.07 (95% CI, 1.06-1.09); 18 studies; n = 227 530; I²  = 32.7%). No significant differences in other secondary outcomes or significant subgroup differences between liveborn singletons and multiple pregnancies were observed. The network meta-analysis showed a significantly lower risk for LBW following frozen-blastocyst vs fresh-blastocyst (RR, 0.76 (95% CI, 0.60-0.95)) or fresh-cleavage (RR, 0.74 (95% CI, 0.59-0.93)) transfer. Frozen-blastocyst transfer was associated with an increased risk for perinatal death compared with the fresh-cleavage method (RR, 2.06 (95% CI, 1.10-3.88)). The higher probability of a male neonate following blastocyst transfer remained evident in the network comparisons. All outcomes were assessed to be of very-low certainty of evidence.

CONCLUSIONS

Current very-low certainty of evidence shows that there may be little-to-no difference in the risk for congenital anomaly or adverse perinatal outcome of pregnancy following blastocyst- vs cleavage-stage embryo transfer, although there was a slightly increased probability of a male neonate following blastocyst transfer. When considering cryopreservation, frozen-blastocyst transfer was associated with a reduction in the risk for LBW compared with both fresh-transfer modalities, and fresh-cleavage transfer may be associated with a reduction in the risk for perinatal death compared with frozen-blastocyst transfer. High-quality RCTs with separate data on fresh and frozen cycles and consistent reporting of culture conditions and freezing methods are mandatory. Individual participant data meta-analyses are required to address the substantial inconsistency resulting from current aggregate data approaches. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Epigenetic Risks of Medically Assisted Reproduction

Since the birth of Louise Joy Brown, the first baby conceived via in vitro fertilization, more than 9 million children have been born worldwide using assisted reproductive technologies (ART). In vivo fertilization takes place in the maternal oviduct, where the unique physiological conditions guarantee the healthy development of the embryo. During early embryogenesis, a major wave of epigenetic reprogramming takes place that is crucial for the correct development of the embryo. Epigenetic reprogramming is susceptible to environmental changes and non-physiological conditions such as those applied during in vitro culture, including shift in pH and temperature, oxygen tension, controlled ovarian stimulation, intracytoplasmic sperm injection, as well as preimplantation embryo manipulations for genetic testing. In the last decade, concerns were raised of a possible link between ART and increased incidence of imprinting disorders, as well as epigenetic alterations in the germ cells of infertile parents that are transmitted to the offspring following ART. The aim of this review was to present evidence from the literature regarding epigenetic errors linked to assisted reproduction treatments and their consequences on the conceived children. Furthermore, we provide an overview of disease risk associated with epigenetic or imprinting alterations in children born via ART.

Perinatal outcomes of singletons born after blastocyst or cleavage-stage embryo transfer in FET cycles

PURPOSE

To compare perinatal outcomes of singletons after blastocyst versus cleavage-stage embryo transfer in frozen-thawed embryo transfer (FET) cycles.

METHODS

This was a retrospective cohort study of 4835 women who conceived after frozen-thawed embryo transfer and delivered a singleton baby from January 2015 to March 2020. The perinatal outcomes of the singletons born after blastocyst transfer (N = 3364) were compared to the singletons born after cleavage-stage transfer (N = 1471), including gestational week, birth weight, newborn gender and Apgar score.

RESULTS

Univariate and multivariate analysis found that infants born after blastocyst transfer had a higher risk of preterm birth (PTB) [adjusted odds ratio (aOR) 1.480; 95% confidence interval (CI) 1.213-1.807], large for gestational age (LGA) (aOR 1.329, 95%CI 1.149-1.536) and very large for gestational age (VLGA) (aOR 1.317, 95%CI 1.092-1.590) compared to infants born after cleavage-stage embryo transfer. When categorized by gestational weeks, the proportion of LGA was significantly higher for boys born after BT between GW 37 to 41 (aOR 1.301, 95%CI 1.051-1.609) and for girls born after BT between GW 32 to 41 (aOR 2.690, 95%CI 1.154-6.271, aOR 1.377, 95%CI 1.094-1.733), compared to boys and girls born after CT.

CONCLUSION

Our data suggested that the risk of PTB and LGA increased after blastocyst transfer versus cleavage-stage embryo transfer in FET cycles, and the risk of LGA is more apparent in the last trimester of pregnancy. Further studies are needed to confirm our findings and explored the association between the extended embryo culture and long-term outcomes of offspring.

Obstetric and perinatal outcomes of singleton pregnancies after blastocyst-stage embryo transfer compared with those after cleavage-stage embryo transfer: a systematic review and cumulative meta-analysis

BACKGROUND

Extended embryo culture to blastocyst stage is widely used in IVF and is the default strategy in most clinics. The last decade has witnessed a growing interest in obstetric-perinatal outcomes following blastocyst transfer. Recent studies have challenged the conclusions of systematic reviews that associate risks of preterm birth (PTB) and large for gestational age (LGA) babies with blastocyst transfer. A higher proportion of blastocysts is transferred as frozen-thawed embryos, which may also have added implications.

OBJECTIVE AND RATIONALE

The aim of this study was to conduct an updated systematic review of the obstetric-perinatal outcomes in singleton pregnancies following blastocyst-stage transfer compared to cleavage-stage transfer in IVF/ICSI cycles. Where deemed appropriate, data were combined in cumulative meta-analyses.

SEARCH METHODS

Data sources from Medline, EMBASE, CINAHL, Web of Science, the Cochrane Central Register of Clinical Trials and the International Clinical Trials Registry Platform (ICTRP) (1980-2020) were searched using combinations of relevant keywords. Searches had no language restrictions and were limited to human studies. Observational studies and randomized controlled trials comparing obstetric-perinatal outcomes between singleton pregnancies after blastocyst-stage transfer and those after cleavage-stage transfer in IVF/ICSI cycles were sought. Two independent reviewers extracted data in 2 × 2 tables and assessed the methodological quality of the relevant studies using the Critical Appraisal Skills Programme scoring. Cumulative meta-analyses were carried out with independent analysis of pregnancies after fresh and frozen embryo transfers, using the Comprehensive Meta-Analysis software. If provided by included studies, adjusted effect sizes were combined in a sensitivity analysis.

OUTCOMES

A total of 35 studies were included (n = 520 769 singleton pregnancies). Outcome data suggest singleton pregnancies following fresh blastocyst transfer were associated with higher risk of LGA (risk ratio (RR) 1.14; 95% CI 1.05-1.24) and very PTB (RR 1.17; 95% CI 1.08-1.26) compared to fresh cleavage-stage transfer. Singleton pregnancies following frozen blastocyst transfer were associated with higher risks of LGA (RR 1.17; 95% CI 1.08-1.27), PTB (RR 1.13; 95% CI 1.03-1.24) and caesarean section (RR 1.08; 95% CI 1.03-1.13) but lower risks of small for gestational age (RR 0.84, 95% CI 0.74-0.95) and perinatal mortality (RR 0.70; 95% CI 0.58-0.86). Increased risks of LGA and PTB after frozen blastocyst transfer persisted in the sensitivity analysis, which also showed a significantly increased risk of PTB after fresh blastocyst transfer. Cumulative meta-analyses revealed consistency in prevalence and magnitude of risks for a number of years. Data on other perinatal outcomes are still evolving.

WIDER IMPLICATIONS

While the available evidence is predominantly reassuring in the context of blastocyst-stage embryo transfer, observational data suggest that blastocyst transfer is associated with a higher risk of LGA. This holds true irrespective of fresh or frozen transfer. Meta-analysis of adjusted data showed an increased risk of PTB with fresh and frozen blastocyst transfer. However, the quality of available evidence ranges from low to very low. Although blastocyst-stage embryo transfer remains the default position in most centres, based on individual risk profile we may need to consider cleavage-stage embryo transfer in some to mitigate the risk of LGA/PTB.

Embryo Culture Media Influence on Live Birth Rate and Birthweight after IVF/ICSI: A Systematic Review Comparing Vitrolife G5 Media to Other Common Culture Media

Previous studies have indicated that culture media vary in efficiency and outcomes, such as live birth rate, birthweight and embryo quality. Does Vitrolife G5 series culture media result in higher live birth rates and birthweight compared to other common culture media? This study is a systematic review based on the PRISMA criteria. Relevant search terms, mesh terms (PubMed and Cochrane) and Emtree terms (Embase) were identified. We searched the literature using PubMed, Embase and Cochrane, on November 10, 2019. The inclusion criteria involved published articles in English comparing Vitrolife G5 to other common culture media. We included randomized controlled trials (RCTs) and cohort studies. The quality of the studies was assessed using the Cochrane Risk of Bias tool 2.0 and the Newcastle-Ottawa Scale. Primary outcomes were live birth rate and birthweight. Secondary outcomes were fertilization rate, implantation rate, biochemical pregnancy rate, clinical pregnancy rate, miscarriage rate, multiple pregnancies and congenital malformations. Of 187 articles screened, 11 studies fulfilled the inclusion criteria: Five RCTs and six retrospective cohort studies. Only one study reported live birth rate, showing a non-significantly higher live birth rate for Vitrolife G5 media. Birthweight had equivocal results with three of six studies, showing significantly lower (2)/higher (1) birthweights, whereas the others were non-significant. Overall, there were no significant differences concerning secondary outcomes. The results are equivocal, and we need more studies to evaluate culture media and their effect on short- and long-term health.

Higher estradiol levels are associated with lower neonatal birthweight after fresh and frozen embryo transfers. A cohort study of 3631 singleton IVF pregnancies

AIM

To assess the birthweight of neonates conceived after fresh and frozen embryo transfers (FET) and, if different, to investigate whether estradiol levels during the late follicular phase were associated with the observed difference.

METHODS

Singleton pregnancies from fresh and FET transfers between January 1990 and December 2013 were compared retrospectively. A total of 2885 singleton pregnancies after fresh embryo transfer and 746 after FET were analyzed. Obstetric and neonatal outcomes were compared between fresh and FET cycles.

RESULTS

The singletons born after FET were found to have a significantly higher birth weight (3313 g), compared to those born after fresh embryo transfer (3143 g); p < .001. The main predictor of this difference was found to be estradiol levels at the end of the follicular phase. The difference in birthweight was inversely correlated to estradiol levels considering all cycles together but also considering fresh and frozen cycles separately.

CONCLUSIONS

Our study demonstrates a link between high estradiol levels and low birth weight of singletons after IVF both in fresh and frozen-thawed embryo transfer cycles. It provides additional support to the involvement of hyperestrogenemia in the process of implantation and on the subsequent fetal development.

Perinatal outcomes in singleton pregnancies after in vitro fertilization cycles over 24 years

OBJECTIVE

To determine how a shift in clinical practice along with laboratory changes has impacted singleton perinatal outcomes after autologous in vitro fertilization (IVF) cycles.

DESIGN

Retrospective cohort.

SETTING

Single academic fertility clinic.

PATIENT(S)

Singleton live births resulting from all IVF cycles (n = 14,424) from August 1, 1995 to October 31, 2019.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Live birth weight, large for gestational age (GA), small for GA, and preterm birth.

RESULT(S)

The entire cohort consisted of 9,280 fresh and 5,144 frozen IVF cycles. Maternal age, parity, body mass index, neonatal sex, and GA at delivery were similar in both groups. There was a decrease in adjusted birth weight per year over the study period for the entire cohort of IVF cycles (-4.42g, 95% confidence interval [CI]: -6.63g to -2.22g). Rates of large for GA newborns decreased by 1.7% (95% CI: 2.9% to 0.6%) annually across the entire cohort of IVF cycles. Furthermore, there was a decrease in annual rates of preterm birth before 32 weeks by 3.2% (95% CI: 5.9% to 0.5%) across the entire cohort of IVF cycles. Trends were also seen in annual reduction of rates of preterm birth before 37 and 28 weeks.

CONCLUSION(S)

With the gradual evolution of clinical and IVF laboratory practices, there has been a decrease in birth weight over 24 years for the entire cohort of IVF cycles. Concurrently, noteworthy practice changes have resulted in an improvement in IVF outcomes with decreased rates of large for GA newborns and preterm birth before 32 weeks for the entire cohort of IVF cycles.

Current Advancements in Noninvasive Profiling of the Embryo Culture Media Secretome

There have been over 8 million babies born through in vitro fertilization (IVF) and this number continues to grow. There is a global trend to perform elective single embryo transfers, avoiding risks associated with multiple pregnancies. It is therefore important to understand where current research of noninvasive testing for embryos stands, and what are the most promising techniques currently used. Furthermore, it is important to identify the potential to translate research and development into clinically applicable methods that ultimately improve live birth and reduce time to pregnancy. The current focus in the field of human reproductive medicine is to develop a more rapid, quantitative, and noninvasive test. Some of the most promising fields of research for noninvasive assays comprise cell-free DNA analysis, microscopy techniques coupled with artificial intelligence (AI) and omics analysis of the spent blastocyst media. High-throughput proteomics and metabolomics technologies are valuable tools for noninvasive embryo analysis. The biggest advantages of such technology are that it can differentiate between the embryos that appear morphologically identical and has the potential to identify the ploidy status noninvasively prior to transfer in a fresh cycle or before vitrification for a later frozen embryo transfer.

Perinatal outcomes in singleton live births after fresh blastocyst-stage embryo transfer: a retrospective analysis of 67 147 IVF/ICSI cycles

STUDY QUESTION

Are perinatal outcomes different between singleton live births conceived from fresh blastocyst transfer and those following the transfer of fresh cleavage-stage embryos?

SUMMARY ANSWER

Fresh blastocyst transfer does not increase risks of preterm birth (PTB), low/high birth weight or congenital anomaly and does not alter the sex ratio at birth or prejudice the chance of having a healthy baby.

WHAT IS KNOWN ALREADY

Extended embryo culture is currently considered the best option for embryo selection, but concerns have been raised about increased risks of preterm delivery and large-for-gestational-age (LGA) babies.

STUDY DESIGN, SIZE, DURATION

We conducted a retrospective cohort study based on data from the Human Fertilisation and Embryology Authority (HFEA) anonymised and cycle-based dataset in the UK between 1999 and 2011.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Baseline characteristics were compared between in vitro fertilisation (IVF)/intracytoplasmic sperm injection (ICSI) blastocyst-stage and cleavage-stage embryo transfer cycles using the χ2 test for categorical/dichotomised covariates and the Mann-Whitney test for continuous covariates. Statistical significance was set at <0.005. Poisson regression and multinomial logistic regression were used to establish relationships between perinatal outcomes and blastocyst-stage embryo transfer or cleavage-stage embryo transfer. Risk ratios (RRs), adjusted risk ratios (aRRs) and their 99.5% confidence intervals (CIs) were calculated as a measure of strength of associations. Results were adjusted for clinically relevant covariates. A sub-group analysis included women undergoing their first IVF/ICSI treatment. The level of significance was set at <0.05, and 95% CIs were calculated in the sub-group analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

Of a total of 67 147 IVF/ICSI cycles, 11 152 involved blastocyst-stage embryo(s) and 55 995 involved cleavage-stage embryo(s). The two groups were comparable with regards to the risk of PTB (aRR, 1.00; 99.5% CI, 0.79-1.25), very-preterm birth (VPTB) (aRR, 1.00; 99.5% CI, 0.63-1.54), very-low birth weight (VLBW) (aRR, 0.84; 99.5% CI, 0.53-1.34), low birth weight (LBW) (aRR, 0.92; 99.5% CI, 0.73-1.16), high birth weight (HBW) (aRR, 0.94; 99.5% CI, 0.75-1.18) and very-high birth weight (VHBW) (aRR, 1.05; 99.5% CI, 0.66-1.65). The risk of congenital anomaly was 16% higher in the blastocyst-stage group than in the cleavage-stage group, but this was not statistically significant (aRR, 1.16; 99.5% CI, 0.90-1.49). The chance of having a healthy baby (born at term, with a normal birth weight and no congenital anomalies) was not altered by extended culture (aRR, 1.00; 99.5% CI, 0.93-1.07). Extended culture was associated with a marginal increase in the chance having a male baby in the main cycle-based analysis (aRR, 1.04; 99.5% CI, 1.01-1.09) but not in the sub-group analysis of women undergoing their first cycle of treatment (aRR, 1.04; 95% CI, 1.00-1.08). In the sub-group analysis, the risk of congenital anomalies was significantly higher after blastocyst-stage embryo transfer (aRR, 1.42; 95% CI, 1.12-1.81).

LIMITATIONS, REASONS FOR CAUTION

This study is limited by the use of observational data and inability to adjust for key confounders, such as maternal smoking status and body mass index (BMI), which were not recorded in the HFEA dataset. As the main analysis was cycle-based and we were unable to link cycles within women undergoing more than one IVF/ICSI cycle, we undertook a sub-group analysis on women undergoing their first treatment cycle.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings should reassure women undergoing blastocyst-stage embryo transfer. For the first time, we have shown that babies born after blastocyst transfer have a similar chance of being healthy as those born after cleavage-stage embryos transfer.

STUDY FUNDING/COMPETING INTEREST(S)

The research activity of Dr Nicola Marconi was funded by the scholarship 'A. Griffini-J. Miglierina', Fondazione Comunitaria del Varesotto, Provincia di Varese, Italy. The authors do not have any competing interests to disclose.

TRIAL REGISTRATION NUMBER

N/A.

Effect of paternal body mass index on neonatal outcomes of singletons after frozen-thawed embryo transfer cycles: analysis of 7,908 singleton newborns

OBJECTIVE

To investigate the effect of paternal body mass index (BMI) on neonatal outcomes of singletons after frozen-thawed embryo transfer (FET) cycles.

DESIGN

Retrospective cohort study.

SETTING

Tertiary-care academic medical center.

PATIENT(S)

A total of 7,908 singleton newborns were divided into four categories based on their paternal BMI: 284 (3.6%) infants were in the paternal underweight category, 4,678 (59.2%) infants were in the paternal normal weight category, 2,585 (32.7%) infants were in the paternal overweight category, and 361 (4.6%) infants were in the paternal obesity category. In addition, we included only infants of women with normal BMI (18.5 kg/m² ≤ BMI < 25 kg/m²).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Neonatal outcomes.

RESULT(S)

The rates of large for gestational age (LGA) infants were significantly higher among those in the paternal overweight and obesity categories than those in the paternal underweight categories. The rates of very LGA were higher among infants in the paternal overweight categories and lower among infants in the paternal underweight categories than the rates in normal controls. The rates of fetal macrosomia were higher among infants in the paternal overweight categories than among infants in the paternal normal weight categories. Compared with normal controls, Z-scores (gestational age- and sex-adjusted birthweight) were significantly higher among the infants in the paternal overweight and paternal obesity categories and significantly lower among the infants in the paternal underweight categories. A positive association was observed in a multiple linear regression model between paternal BMI and newborn birthweights after adjustment for several potential confounders.

CONCLUSION(S)

Paternal BMI had an independent impact on the birthweight of singletons born after FET cycles. Paternal overweight and paternal obesity were independent risk factors for having LGA infants after FET cycles. Furthermore, paternal overweight was an independent risk factor for fathering infants with macrosomia or very LGA infants after FET cycles.

The impact of selected embryo culture conditions on ART treatment cycle outcomes: a UK national study

STUDY QUESTION

Are selected embryo culture conditions namely media, oxygen level, and incubator type, associated with IVF live birth rate (LBR) and the health of singleton offspring at birth?

SUMMARY ANSWER

There were statistically significant differences in LBR between the eight culture media systems analysed; however, none of the embryo culture factors showed statistically significant associations with birth weight (BW) in multivariable regression analyses.

WHAT IS KNOWN ALREADY

In clinical ART culture media is the initial environment provided for the growth of human embryos. Pre-implantation development is a critical period of developmental plasticity, which could have long-lasting effects on offspring growth and health. Although some studies have shown an impact of culture medium type on BW, the interaction between culture medium type and associated culture conditions on both treatment success rates (LBR) and offspring BW is largely unexplored. This study aimed to examine these factors in a large multicentre national survey capturing the range of clinical practice.

STUDY DESIGN, SIZE, DURATION

In this cross-sectional study, data from a survey circulated to all UK IVF clinics requesting information regarding culture medium type, incubator type, and oxygen level used in ART between January 2011 and December 2013 were merged with routinely recorded treatment and outcome data held in the Human Fertilisation and Embryology Authority Register up to the end of 2014.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Forty-six (62%) UK clinics responded to the survey. A total of 75 287 fresh IVF/ICSI cycles were captured, including 18 693 singleton live births. IVF success (live birth, singleton or multiple; LB), singleton gestation and singleton gestation-adjusted BW were analysed using logistic and linear regression models adjusting for patient/treatment characteristics and clinic-specific effects.

MAIN RESULTS AND THE ROLE OF CHANCE

Culture medium type was shown to have some impact on LBR (multivariable logistic regression, (MRL); post-regression Wald test, P < 0.001), but not on BW (MLR; post-regression Wald test, P = 0.215). However, blastocyst culture had the largest observed effect on odds of LBR (odds ratio (OR) = 1.35, CI: 1.29–1.42), increased the risk of pre-term birth even when controlling for oxygen tension (MLR; OR = 1.42, CI: 1.23–1.63), and gestation-adjusted BW (MLR, β = 38.97 g, CI: 19.42–58.53 g) when compared to cleavage-stage embryo culture. We noted a very strong effect of clinic site on both LBR and BW, thus confounding between treatment practices and clinic site may have masked the effect of culture conditions.

LIMITATIONS, REASONS FOR CAUTION

Larger datasets with more inter-centre variation are also needed, with key embryo culture variables comprehensively recorded in national treatment registries.

WIDER IMPLICATIONS OF THE FINDINGS

This study is the largest investigation of laboratory environmental effects in IVF on both LBR and singleton BW. Our findings largely agree with the literature, which has failed to show a consistent advantage of one culture media type over another. However, we noted some association of LBR with medium type, and the duration of embryo exposure to laboratory conditions (blastocyst culture) was associated with both LBR and singleton health at birth. Because of the strong effect of clinic site noted, further randomized controlled trials are needed in order to reliably determine the effect of embryo culture on IVF success rates and the growth and health of subsequent offspring.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the EU FP7 project grant EpiHealthNet (FP7-PEOPLE-2012-ITN -317 146). The authors have no competing interests to declare.

Increased blood pressure and impaired endothelial function after accelerated growth in IVF/ICSI children

STUDY QUESTION

What is the effect of growth velocity (height and weight) in early infancy on metabolic end-points and endothelial function in children born after ART?

SUMMARY ANSWER

Neonatal, infant and childhood growth is positively related to blood pressure in 9-year-old IVF/ICSI offspring, while growth in childhood was negatively associated with endothelial function.

WHAT IS KNOWN ALREADY

Offspring of pregnancies conceived after ART are at risk for later cardiometabolic risk factors. It is well established that early growth is related to numerous later cardiometabolic risk factors such as high blood pressure. This concept is known as the Developmental Origin of Health and Disease theory.

STUDY DESIGN SIZE DURATION

The relation between early growth and later cardiometabolic risk profile was studied in the MEDIUM-KIDS study, a prospective observational cohort study in children born after an IVF/ICSI treatment. In 131 children (48.1% males) at the average age of 9.4 years, cardiometabolic outcomes were assessed and growth data from birth until age 9 years were collected from child welfare centers.

PARTICIPANTS/MATERIALS SETTINGS METHODS

The following cardiometabolic outcomes were assessed: blood pressure, skinfolds, lipid spectrum, hair cortisone and glucose and insulin levels. Data on maximum skin perfusion after transdermal delivery of acetylcholine as a measure of endothelial function were collected.Growth charts were obtained electronically from child welfare centers, which offer free consultations and vaccinations to all Dutch children. At these centers, height and weight are recorded at predefined ages. Growth was defined as z-score difference in weight between two time points. Multivariable linear regression analysis was used to model the relation between growth and cardiometabolic outcomes. The following growth windows were -studied simultaneously in each model: 0-1 month, 1-3 months, 3-6 months, 6-11 months, 11-24 months and 2-6 years. The model was adjusted for height growth in all intervals except for 0-1 month.

MAIN RESULTS AND THE ROLE OF CHANCE

In multivariable linear regression analyses, multiple growth windows were positively associated with blood pressure, for example growth from 2-6 years was significantly related to systolic blood pressure: B = 4.13, P = 0.005. Maximum skin perfusion after acetylcholine was negatively associated with height-adjusted weight gain from 2 to 6 years: B = -0.09 (log scale), P = 0.03. Several growth windows (weight 1-3 months, 3-6 months, 6-11 months, 11-24 months, 2-6 years) were positively linked with total adiposity. Lipids, glucose tolerance indices and cortisone were not related to growth.

LIMITATIONS REASONS FOR CAUTION

This study is of modest size and of observational nature, and we did not include a control group. Therefore, we cannot assess whether the observed associations are causal. It is also not possible to analyze if our observations are specific for, or exacerbated in, the ART population. Ideally, a control group of naturally conceived siblings of IVF/ICSI children should simultaneously be studied to address this limitation and to assess the impact of the ART procedure without the influence of parental (subfertility) characteristics.

WIDER IMPLICATIONS OF THE FINDINGS

The results of this study contribute to our understanding of the reported increased risk for hypertension in ART offspring. We speculate that early, accelerated growth may be involved in the reported increased risk for hypertension in ART offspring, with endothelial dysfunction as a possible underlying mechanism. However, additional research into the mechanisms involved is required.

STUDY FUNDING/COMPETING INTERESTS

The study was financially supported by the March of Dimes, grant number #6-FY13-153. The sponsor of the study had no role in study design, data collection, data analysis, data interpretation or writing of the paper. The authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

NTR4220.

Birthweight of singletons born after blastocyst-stage or cleavage-stage transfer: analysis of a data set from three randomized controlled trials

PURPOSE

The present post hoc analysis aims to study the neonatal data of singletons born from three randomized controlled trials (RCTs) which compared the outcome of day 3 and day 5 transfers.

METHODS

Our analysis included 208 liveborn singletons from three existing RCTs (publication dates 2004, 2005, and 2006), 93 children from cleavage-stage transfers and 115 from blastocyst-stage transfers. Vanishing twins were excluded from the analysis. Singleton birthweight was the primary outcome measure. Gestational age and gender of the newborn were accounted for in the multiple regression analysis, along with other confounding factors, such as maternal age, BMI, parity, and smoking behavior.

RESULTS

There was no significant difference in gestational age (median, interquartile range) between cleavage-stage transfer (275 days; 267-281) and blastocyst-stage transfer (277 days; 270-281; p = 0.22). Singleton birthweight (median, interquartile range) was not significantly different between cleavage-stage transfer (3330 g; 3020-3610) and blastocyst-stage transfer (3236 g; 2930-3630; p = 0.40), even following multivariable regression analysis to control for potential maternal and newborn confounders.

CONCLUSION

The gestational age and birthweight were not significantly different after cleavage-stage and blastocyst-stage transfers. One limitation to be recognized is the age of the data, with original data collection dates from 2001 to 2004. Additionally, the RCTs used for the present analysis have a fairly young age restriction.

Obstetric and neonatal outcome of ART in patients with polycystic ovary syndrome: IVM of oocytes versus controlled ovarian stimulation

STUDY QUESTION

Does IVM of immature oocytes retrieved from small antral follicles in women with polycystic ovary syndrome (PCOS) have an impact on obstetric and neonatal outcomes compared to controlled ovarian stimulation (COS)?

SUMMARY ANSWER

Obstetric and neonatal outcomes after IVM appear to be similar to those after COS.

WHAT IS KNOW ALREADY

Women with PCOS have an increased risk of adverse pregnancy outcomes and congenital malformations in their offspring. For patients with PCOS who require IVF, IVM of germinal vesicle (GV)-stage oocytes retrieved from antral follicles has been adopted as a mild approach ART, with improved pregnancy rates over the last two decades. Although reports of obstetrical and neonatal outcomes after IVM have been reassuring, the limited sample sizes in previous studies preclude firm conclusions, and further study is warranted.

STUDY DESIGN, SIZE, DURATION

This is a retrospective observational study analysing obstetric and neonatal data from 1036 clinical pregnancies in unique patients with PCOS who conceived following a cycle of IVM or COS between January 2010 and December 2016 in a tertiary reproductive centre. In total, 393 singleton pregnancies with a gestational age beyond 20 weeks were included. A phenotypic approach was used for the diagnosis of PCOS. Pregnancies following oocyte donation, standard IVF (as opposed to ICSI) or preimplantation genetic testing and pregnancies requiring testicular biopsy in the male partners were excluded.

PARTICIPANTS/MATERIALS,SETTING, METHODS

Pregnancy outcomes were analysed in women with PCOS phenotype A, C or D, as defined by different combinations of the Rotterdam criteria. Data from 164 pregnancies beyond 20 weeks after IVM were compared with those from 229 pregnancies after COS. Pregnancies in the IVM group were obtained after minimal ovarian stimulation and IVF with ICSI of transvaginally collected GV oocytes that had reached the metaphase II stage in vitro after 28 to 40 h of culture. No hCG trigger was administered before oocyte retrieval. Outcome measures were analysed or reported in singleton pregnancies only and included adverse obstetric events and neonatal health parameters, in particular birthweight, prematurity, small-for-gestational age, large-for-gestational age, perinatal death and major/minor malformation rates. The incidence of hypertensive disorders of pregnancy (HDP) and birthweight was analysed by multiple linear and logistic regression, adjusted for relevant treatment variables and maternal characteristics.

MAIN RESULTS AND THE ROLE OF CHANCE

The IVM and the COS groups differed significantly (P < 0.001) for maternal circulating AMH levels and PCOS phenotype distribution, with more of the PCOS phenotype A in the IVM group. Pregnant women in the IVM group were younger than pregnant women in the COS group (P = 0.05). With regard to obstetric complications in singleton pregnancies, in the unadjusted analysis, mothers of infants in the IVM group more often had HDP (29/164 (17.9%) vs 22/229 (9.6%), P = 0.02) compared with mothers in the COS group. Singletons born after IVM and COS had a similar birthweight standard deviation score (SDS) (0.51 ± 0.94 after IVM vs 0.33 ± 1.05 after COS, P = 0.19). Preterm birth rate (32–36.9 weeks) and early preterm birth rate (<32 weeks) were also similar in both groups. The total malformation rate was 4.1% in singletons after IVM and 2.4% in singletons after COS. Multivariate linear regression analysis accounting for relevant confounders demonstrated that parity was the only independent predictive factor (P = 0.04) for birthweight SDS. Multivariate logistic regression analysis showed that BMI, parity and type of ART (IVM as opposed to COS) were significantly correlated with the incidence of HDP. Only patients with the PCOS phenotype A showed a tendency towards a higher risk of HDP in those who underwent IVM compared to those who had COS.

LIMITATIONS, REASONS FOR CAUTION

The study is limited by its retrospective nature and loss to follow-up of a subset of children with no information regarding congenital malformations. Furthermore, the paediatricians who assessed the children after birth were not blinded for the type of ART procedure.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides further evidence that, compared to COS, IVM of oocytes derived from small antral follicles does not adversely affect the neonatal health of the offspring of patients with PCOS. The observed increased risk of HDP in patients with PCOS phenotype A following IVM treatment warrants further scrutiny.

STUDY FUNDING/COMPETING INTEREST(S)

Translational IVM research at Universitair Ziekenhuis Brussel (UZ Brussel) and Vrije Universiteit Brussel (VUB) has been supported by grants from the Institute for the Promotion of Innovation by Science and Technology in Flanders (Agentschap voor Innovatie door Wetenschap en Technologie—IWT, project 110680), the Fund for Research Flanders (Fonds Wetenschappelijk Onderzoek–Vlaanderen—FWO, project G.0343.13) and the Belgian Foundation Against Cancer (HOPE project, Dossier C69). Clinical IVM research was supported by research grants from Cook Medical and Besins Healthcare. M.D.V. reports honoraria for lectures from Cook Medical and Besins Healthcare outside the submitted work. S.S.R. reports honoraria for lectures by MSD and Besins and research grants by MSD, Ferring and Merck Serono outside of the submitted work. C.B. reports personal fees from Merck-Serono, Ferring, IBSA, Finox, MSD and Abbott outside the submitted work. H.T. reports grants from Merck, MSD, Goodlife, Cook, Roche, Besins, Ferring, Mithra (now Allergan) and the Research Fund of Flanders (FWO) and consultancy fees from Finox, Abbott, Obseva and Ovascience outside the submitted work. The other authors have nothing to disclose.

Birthweight of singletons born after cleavage-stage or blastocyst transfer in fresh and warming cycles

STUDY QUESTION

Does extended culture to the blastocyst stage affect singleton birthweight after either fresh or vitrified-warmed embryo transfer?

SUMMARY ANSWER

Singleton birthweight z-scores did not vary significantly after a fresh blastocyst transfer, whereas the additional effect of vitrification remains inconclusive.

WHAT IS KNOWN ALREADY

Observational studies have associated extended culture with an increased risk of preterm birth and low birthweight. On the contrary, in terms of birthweight and gestational age, singletons born after vitrification have been associated with a better perinatal outcome when compared to those born following a fresh transfer.

STUDY DESIGN, SIZE, DURATION

Our post-hoc cohort analysis on neonatal outcomes included 447 liveborn singletons was derived from a recent retrospective analysis on cumulative live birth rates after cleavage-stage and blastocyst transfers. These babies were born following a fresh single cleavage-stage transfer (FCT Day 3, n = 113), fresh single blastocyst transfer (FBT Day 5, n = 218), vitrified-warmed cleavage-stage transfer (VCT Day 3, n = 58) or vitrified-warmed blastocyst transfer (VBT Day 5, n = 58).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Singleton birthweight was the primary outcome measure. Gestational age and gender of the newborn were accounted for by using birthweight z-scores in a multivariable linear regression analysis, adjusting for other confounders (maternal age, BMI, parity and smoking behaviour). Vanishing twins were excluded from the analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

A significantly lower z-score was observed after blastocyst transfer compared to cleavage-stage transfer in the vitrified-warmed Day 5 group (P = 0.013), a difference not observed in the fresh transfer groups (P = 0.32). Following multivariable regression analysis [adjusted regression coefficient (95% confidence interval)], the FCT and FBT groups showed no significant influence on the birthweight z-scores after fresh transfer [-0.19 (-0.44; 0.05)], but the transfer of vitrified blastocysts (VBT) was associated with a lower birthweight [-0.52 (-0.90; -0.15)] compared with the transfer of vitrified cleavage-stage embryos (VCT).

LIMITATIONS, REASONS FOR CAUTION

The present cohort was relatively small, especially in the vitrified-warmed subgroups. Pregnancy-associated factors possibly influencing birthweight (such as diabetes, hypertension, pre-eclampsia) were also not accounted for in the analysis.

WIDER IMPLICATIONS OF THE FINDINGS

Different ART procedures, including extended culture and vitrification, may hold potential safety issues. These results require further confirmation in future larger studies.

STUDY FUNDING/COMPETING INTEREST(S)

None.

TRIAL REGISTRATION NUMBER

N/A.

Live birth rate and neonatal outcome following cleavage-stage embryo transfer versus blastocyst transfer using the freeze-all strategy

RESEARCH QUESTION

What are the live birth rates and neonatal outcomes following cleavage-stage embryo transfer and blastocyst transfer in a freeze-all treatment scenario?

DESIGN

This was a retrospective cohort study. All good-quality embryos were frozen on the third day; the remaining embryos were grown on until they reached blastocyst stage and then frozen. Between 2007 and 2016, 11,801 patients underwent cleavage-stage embryo transfer and 1009 patients underwent blastocyst transfer in the first treatment cycle using the freeze-all strategy. The live birth rate and neonatal outcomes were evaluated.

RESULTS

The live birth rate in the first frozen embryo transfer cycle was higher following blastocyst transfer than following cleavage-stage transfer (69.1% versus 55.5%, P < 0.01), but there was no difference in live birth rate in the second frozen embryo transfer cycle between blastocyst transfer and cleavage-stage transfer (45.2% versus 52.7%, P > 0.05). Similarly, no difference was found in the cumulative live birth rate for the first complete IVF cycle (71.1% versus 69.2%, P > 0.05). Blastocyst transfer gave a higher risk of preterm singleton delivery than did cleavage-stage transfer. However, there was no difference in the risk of early preterm delivery, low birth weight, very low birth weight, high birth weight and very high birth weight between the two groups.

CONCLUSIONS

There is no evidence to support the superiority of blastocyst transfer compared with cleavage-stage transfer in a freeze-all treatment scenario. There may be a higher risk of preterm singleton delivery following blastocyst transfer than following cleavage-stage transfer but further studies are needed to verify this.

Effect of embryo and blastocyst transfer on the birthweight of live-born singletons from FET cycles

PURPOSE

To evaluate the effect of culture duration (embryo (day 3) transfer vs. blastocyst (day 5-6) transfer) on the birthweight of singletons from frozen embryo transfer (FET) cycles.

METHODS

A total of 1092 singletons were analyzed in this retrospective study. The distribution of large for gestational age (LGA) infants, the mean birthweight, and z scores of singletons were compared between the day 3 and day 5-6 transfer groups. Multiple linear regression analysis was performed to evaluate the relationships between confounding factors and singleton birthweight.

RESULTS

The proportion of LGA infants significantly increased with BMI (BMI < 20, 12.8%; 20 ≤ BMI ≤ 25, 23.2%; BMI > 25, 32.3%; P < 0.0001). However, the proportions of small for gestational age (SGA) and LGA infants were not significantly different between day 3 and day 5-6 transfers. The absolute mean birthweight of singletons was not significantly different between day 3 transfer (3422 ± 547 g) and day 5-6 transfer (3433 ± 559 g; P = 0.732). The z scores (calculated from a reference population) of singletons were also not significantly different between the two groups (0.499 vs. 0.533, P = 0.625). Multiple linear regression analysis showed that maternal BMI, gestational age, and infant gender had significant effects on singleton birthweight, while culture duration (P = 0.731) did not significantly affect singleton birthweight.

CONCLUSIONS

In vitro culture duration did not affect the birthweight of newborns resulting from day 3 to day 5-6 transfers in FET cycles.

The effect of blastocyst transfer on newborn sex ratio and monozygotic twinning rate: an updated systematic review and meta-analysis

RESEARCH QUESTION

Is blastocyst transfer (BT) associated with a higher offspring secondary sex ratio and monozygotic twinning (MZT)?

DESIGN

A systematic search of PubMed/MEDLINE, Embase, Web of Science, Cochrane Library and Google Scholar databases was carried out for studies published between 1995 and May 2017 using relevant keywords and a meta-analysis performed on selected studies. The analysis was performed using Stata 12.0; odds ratios (OR) and 95% confidence intervals (CI) were used to assess the results for binary studies. Subgroup analyses and meta-regression were also conducted.

RESULTS

Twenty-six studies published between 2001 and May 2017 (sex ratio: 13, MZT: 12, and both sex ratio and MZT: 1) were identified. The analysis showed a significantly higher M/F ratio at birth (OR = 0.89, 95% CI: 0.86 to 0.93, I² = 19.8%) and a higher risk of MZT (OR = 0.37, 95% CI: 0.22 to 0.60, I² = 75.2%) after BT compared with cleavage-stage embryo transfer (CT). Furthermore, a subgroup analysis was performed based on studies published after 2009; results were found to be consistent with the 2009 meta-analysis.

CONCLUSIONS

This meta-analysis provides an update and stronger evidence to support the observation that BT is associated with a higher proportion of males and an increased risk of MZT. In clinical practice, these BT-associated neonatal outcomes should be taken into account when counselling infertility patients.

Birthweight in infants conceived through in vitro fertilization following blastocyst or cleavage-stage embryo transfer: a national registry study

PURPOSE

In vitro fertilization (IVF) infants have lower birthweights than their peers, predisposing them to long-term health consequences. Blastocyst transfer (BT), at day 5-6 post-fertilization, is increasing in usage, partially due to improved pregnancy outcomes over cleavage-stage transfer (CT, day 2-3). Data to date, however, have been inconclusive regarding BT's effects on birthweight.

METHODS

Participants included all US autologous, single-gestation, fresh embryo transfer cycles initiated from 2007 to 2014 that resulted in a term infant (N = 124,154) from the National Assisted Reproductive Technology Surveillance System. Generalized linear models including obstetric history, maternal demographics, and infant sex and gestational age were used to compare birthweight outcomes for infants born following BT (N = 67,169) with infants born following CT (N = 56,985) and to test for an interaction between transfer stage and single embryo transfer (SET).

RESULTS

Infants born following BT were 6 g larger than those born following CT (p = 0.04), but rates of macrosomia (RR 1.00, 95% CI 0.96-1.04) and low birthweight (LBW, RR 1.00, 95% CI 0.93-1.06) were not different between the groups. The interaction between SET and transfer stage was significant (p = 0.02). Among SET infants, BT was associated with 19.26 g increased birthweight compared to CT (p = 0.008).

CONCLUSIONS

The increase in birthweights identified following BT is unlikely to be clinically relevant, as there were no differences in rates of macrosomia or LBW. These findings are clinically reassuring and indicate that the increasing use of BT is unlikely to further decrease the on average lower birthweights seen in IVF infants compared to their naturally conceived peers.

Continuous embryo culture elicits higher blastulation but similar cumulative delivery rates than sequential: a large prospective study

PURPOSE

To assess whether continuous embryo culture involves better embryological and/or clinical outcomes than sequential.

METHODS

Prospective study at a private IVF center. All consecutive IVF cycles (September 2013-2015) fulfilling the inclusion criteria underwent embryo culture in either Continuous-Single-Culture-Media (CSCM, n = 972) or sequential media (Quinn's Advantage, n = 514), respectively. ICSI, blastocyst culture in either standard (MINC) or undisturbed (Embryoscope) incubation, transfer (until September 2016), and pregnancy follow-up (until September 2017) were performed. When aneuploidy testing was required, trophectoderm biopsy and qPCR were performed. Sub-analyses and logistic regression corrected for confounders were performed. The primary outcomes were overall blastocyst rate per oocyte and mean blastocyst rate per cycle. The sample size was defined to reach 95 and 80% statistical power for the former and the latter outcome, respectively. Secondary outcomes were euploidy (if assessed), cumulative delivery rates, gestational age, and birthweight.

RESULTS

Continuous embryo culture resulted into a higher overall blastocyst rate per inseminated oocyte than sequential (n = 2211/5841, 37.9% vs. 1073/3216, 33.4%; p < 0.01), confirmed also from a cycle-based analysis (mean blastocyst rate: 38.7% ± 29.7% vs. 34.3% ± 29.4%; p = 0.01). The continuous media (OR = 1.23), the undisturbed incubation system (OR = 1.22), the maternal age (OR = 0.92), and the sperm factor (OR = 0.85) were outlined as positive predictors of blastulation. However, the cumulative delivery rates per ended cycle (i.e., delivery achieved or no blastocyst produced or left; > 90%) were comparable in the two groups (n = 244/903, 27.0% vs. 129/475, 27.2%). The neonatal outcomes were similar.

CONCLUSIONS

Continuous culture involves better embryological but similar clinical outcomes than sequential. This large prospective study supports the absence of clinical disparity among the two approaches.

Influence of cryopreservation on perinatal outcome after blastocyst- vs cleavage-stage embryo transfer: systematic review and meta-analysis

OBJECTIVE

To compare the perinatal outcomes of singleton pregnancies resulting from blastocyst- vs cleavage-stage embryo transfer and to assess whether they differ between fresh and frozen embryo transfer cycles.

METHODS

A systematic review of the literature was carried out using the Scopus, MEDLINE and ISI Web of Science databases with no time restriction. We included only peer-reviewed articles involving humans, in which perinatal outcomes of singleton pregnancies after blastocyst-stage embryo transfer were compared with those after cleavage-stage embryo transfer. Primary outcomes were preterm birth before 37 weeks and low birth weight (< 2500 g). Secondary outcomes were very preterm birth before 32 weeks, very low birth weight (< 1500 g), small-for-gestational-age (SGA), large-for-gestational-age (LGA), perinatal mortality and congenital anomaly. A meta-analysis was performed using a random-effects model. Three subgroups were evaluated: fresh only, frozen only and fresh plus frozen embryo transfer cycles.

RESULTS

From a total of 3928 articles identified, 14 were selected for qualitative/quantitative analysis. Significantly higher incidences of preterm birth < 37 weeks (11 studies, n = 106 629 participants; risk ratio (RR), 1.15 (95% CI, 1.05 - 1.25); P = 0.002) and very preterm birth < 32 weeks (seven studies, n = 103 742; RR, 1.16 (95% CI, 1.02-1.31); P = 0.03) were observed after blastocyst- than after cleavage-stage embryo transfer in fresh cycles. However, the risk of preterm and very preterm birth was similar after blastocyst- and cleavage-stage transfers in frozen and fresh plus frozen cycles. Overall effect size analysis revealed fewer SGA deliveries after blastocyst- compared with cleavage-stage transfer in fresh cycles but a similar number in frozen cycles. Conversely, more LGA deliveries were observed after blastocyst- compared with cleavage-stage transfer in frozen cycles (two studies, n = 39 044; RR, 1.18 (95% CI, 1.09-1.27); P < 0.0001) and no differences between the two groups in fresh cycles (four studies, n = 42 982; RR, 1.14 (95% CI, 0.97-1.35); P = 0.11). There were no differences with respect to low birth weight, very low birth weight or congenital anomalies between blastocyst- and cleavage-stage transfers irrespective of the cryopreservation method employed. Only one study reported a higher incidence of perinatal mortality after blastocyst- vs cleavage-stage embryo transfer in frozen cycles, while no differences were found in fresh cycles.

CONCLUSIONS

Our results suggest that cryopreservation of embryos can influence outcome of pregnancy conceived following blastocyst- vs cleavage-stage embryo transfer in terms of preterm birth, very preterm birth, LGA, SGA and perinatal mortality. Caution should be exercised in interpreting these findings given the low level of evidence and wide heterogeneity of the studies. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Insulin and branched-chain amino acid depletion during mouse preimplantation embryo culture programmes body weight gain and raised blood pressure during early postnatal life

Mouse maternal low protein diet exclusively during preimplantation development (Emb-LPD) is sufficient to programme altered growth and cardiovascular dysfunction in offspring. Here, we use an in vitro model comprising preimplantation culture in medium depleted in insulin and branched-chain amino acids (BCAA), two proposed embryo programming inductive factors from Emb-LPD studies, to examine the consequences for blastocyst organisation and, after embryo transfer (ET), postnatal disease origin. Two-cell embryos were cultured to blastocyst stage in defined KSOM medium supplemented with four combinations of insulin and BCAA concentrations. Control medium contained serum insulin and uterine luminal fluid amino acid concentrations (including BCAA) found in control mothers from the maternal diet model (N-insulin + N-bcaa). Experimental medium (three groups) contained 50% reduction in insulin and/or BCAA (L-insulin + N-bcaa, N-insulin + L-bcaa, and L-insulin + N-bcaa). Lineage-specific cell numbers of resultant blastocysts were not affected by treatment. Following ET, a combined depletion of insulin and BCAA during embryo culture induced a non sex-specific increase in birth weight and weight gain during early postnatal life. Furthermore, male offspring displayed relative hypertension and female offspring reduced heart/body weight, both characteristics of Emb-LPD offspring. Combined depletion of metabolites also resulted in a strong positive correlation between body weight and glucose metabolism that was absent in the control group. Our results support the notion that composition of preimplantation culture medium can programme development and associate with disease origin affecting postnatal growth and cardiovascular phenotypes and implicate two important nutritional mediators in the inductive mechanism. Our data also have implications for human assisted reproductive treatment (ART) practice.

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Chronic disease may derive from maternal undernutrition during pregnancy, including the periconceptional period.

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Mouse embryos cultured in medium low in insulin and select amino acids gave rise to offspring with disease symptoms.

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We propose these metabolite deficiencies around conception induce adverse programming of the early embryo leading to increased disease risk in later life.

Retrospective comparative study of the factors affecting birthweights in frozen-thawed embryo transfer, compared to fresh embryo transfer

Aim

Several studies have indicated that the cause of the increased birthweight of frozen‐thawed embryos was associated with assisted reproductive technology (ART) procedures, such as cryopreservation. In the present study, the mean birthweight of singletons was compared between the ovulatory and hormone replacement therapy (HRT) cycles in order to investigate the primary factor that leads to higher birthweights from frozen‐thawed embryo transfer (FET).

Methods

This retrospective study was carried out from January 2011 to December 2014 on 2738 singletons who were born at 37‐41 weeks’ gestation, following ART in a single facility. The mean birthweight of the singletons who were born after a fresh embryo transfer (ET) was compared to the mean birthweight of the singletons who were born after a FET. In the FET cycles, the mean birthweight of the singletons was compared between the ovulatory and HRT cycles.

Results

The mean birthweight of the singletons who were born after a FET was significantly higher than that of the singletons who were born after a fresh ET. In the FET cycles, the birthweight from the HRT cycles was significantly higher than that from the ovulatory cycles. Among the HRT cycles, there was no difference between the birthweight of the singleton who were born from a blastocyst transfer and those who were born from a cleavage‐stage ET.

Conclusion

The primary factor to affect the birthweight of singletons might be the pre/postET hormonal environment of the endometrium and not the stage of the transferred embryo nor the frozen‐thawed procedure itself.

Comparative neonatal outcomes in singleton births from blastocyst transfers or cleavage-stage embryo transfers: a systematic review and meta-analysis

BACKGROUND

Comparative neonatal outcomes with respect to singleton births from blastocyst transfers or cleavage-state embryo transfers are controversial with respect to which method is superior. Many studies have yielded contradictory results. We performed a systematic review and meta-analysis for the purpose of comparing neonatal outcomes in single births following IVF/ICSI.

METHODS

We searched the Medline, Embase and Cochrane Central Register of Clinical Trials (CCTR) databases until October 2016. Studies and trials that contained neonatal outcomes for singleton births were included. Data were extracted in 2 × 2 tables. The analysis was performed using Rev Man 5.1 software. Risk ratios (RRs) and risk differences, with 95% confidence intervals, were calculated to assess the results of each outcome. Subgroups were applied in all outcomes. Newcastle-Ottawa scale (NOS) checklists were used to assess the quality of the referenced studies.

RESULTS

Twelve studies met the criteria in this meta-analysis. There was a high risk of preterm birth after blastocyst embryo transfer versus the risk after cleavage-stage transfer (RR: 1.11, 95% CI: 1.01-1.22). For the "only fresh" subgroup, the outcome was coincident (RR: 1.16, 95% CI: 1.06-1.27). For the "fresh and frozen" and "only frozen" subgroups, there were no differences. Patients who received fresh blastocyst embryo transfers had a high risk of very preterm births (RR: 1.16, 95% CI: 1.02-1.31). Finally, cleavage-stage embryo transfers were associated with a high risk of infants who were small for gestational age (0.83, 95% CI: 0.76-0.92) and a low risk of those who were large for gestation age (1.14, 95% CI: 1.04-1.25).

CONCLUSIONS

The risks of preterm and very preterm births increased after fresh blastocyst transfers versus the risks after fresh cleavage-stage embryo transfers. However, in frozen embryo transfers, there were no differences. Blastocyst embryo transfers resulted in high risks of infants who were large for gestational age, and cleavage-stage embryo transfers resulted in high risks of infants who were small for gestational age.

Blastocyst Development in a Single Medium Compared to Sequential Media: A Prospective Study With Sibling Oocytes

The aim of the present study was to compare blastocyst formation rates after embryo culture in a single medium (Global) as compared to sequential media (ISM1/BlastAssist). In this prospective trial with sibling oocytes, 542 metaphase II (ΜΙΙ) oocytes from 31 women were randomly and equally divided to be fertilized and cultured to the blastocyst stage in either sequential media (ISM1/BlastAssist; n = 271 MII oocytes) or a single medium (Global; n = 271 MII oocytes). In both groups, embryos were cultured in an interrupted fashion with media changes on day 3. Embryo transfer was performed on day 5. Blastocyst formation rates on day 5 (61.7% ± 19.9% vs 37.0% ± 25.5%, P < .001) were significantly higher following culture in Global as compared to ISM1/BlastAssist, respectively. Fertilization rates, cleavage rates, and percentage of good quality embryos on day 3 were similar between Global and ISM1/BlastAssist, respectively. The percentages of good quality blastocysts (63.0% ± 24.8% vs 32.1% ± 37.2%, P < .001), blastocysts selected for transfer (27.8% ± 19.2% vs 11.1% ± 14.4%, P = .005), and utilization rates (62.5% ± 24.8% vs 39.0% ± 25.2%, P < .001) were significantly higher in Global as compared to ISM1/BlastAssist, respectively. In conclusion, culture in Global was associated with higher blastocyst formation rates compared to ISM1/BlastAssist, suggesting that the single medium may provide better support to the developing embryo.

Risk of adverse pregnancy and perinatal outcomes after high technology infertility treatment: a comprehensive systematic review

In the literature, there is growing evidence that subfertile patients who conceived after infertility treatments have an increased risk of pregnancy and perinatal complications and this is particularly true for patients who conceived through use of high technology infertility treatments. Moreover, high technology infertility treatments include many concomitant clinical and biological risk factors. This review aims to summarize in a systematic fashion the current evidence regarding the relative effect of the different procedures for high technology infertility treatments on the risk of adverse pregnancy and perinatal outcome. A literature search up to August 2016 was performed in IBSS, SocINDEX, Institute for Scientific Information, PubMed, Web of Science and Google Scholar and an evidence-based hierarchy was used to determine which articles to include and analyze. Data on prepregnancy maternal factors, low technology interventions, specific procedures for male factor, ovarian tissue/ovary and uterus transplantation, and chromosomal abnormalities and malformations of the offspring were excluded. The available evidences were analyzed assessing the level and the quality of evidence according to the Oxford Centre for Evidence-Based Medicine guidelines and the Grading of Recommendations Assessment, Development, and Evaluation system, respectively. Current review highlights that every single procedure of high technology infertility treatments can play a crucial role in increasing the risk of pregnancy and perinatal complications. Due to the suboptimal level and quality of the current evidence, further well-designed studies are needed.

Obstetrical and perinatal outcomes following blastocyst transfer compared to cleavage transfer: a systematic review and meta-analysis

STUDY QUESTION

Is blastocyst transfer safe when compared to cleavage stage embryo transfer regarding obstetric and perinatal outcomes?

SUMMARY ANSWER

The clinical equipoise between blastocyst and cleavage stage embryo transfer remains as the evidence associating blastocyst transfer with some adverse perinatal outcomes is of low/very low quality.

WHAT IS KNOWN ALREADY

Extended embryo culture to the blastocyst stage provides some theoretical advantages and disadvantages. While it permits embryo self-selection, it also exposes those embryos to possible harm due to the in vitro environment. Both effectiveness and safety should be weighed to permit evidence-based decisions in clinical practice.

STUDY DESIGN, SIZE, DURATION

This is a systematic review and meta-analysis of randomized controlled trials (RCTs) and observational studies reporting perinatal outcomes for singletons comparing the deliveries resulting from blastocyst and cleavage stage embryo transfer. Observational studies were included because the primary outcomes, perinatal mortality and birth defects, are rare and require a large number of participants (>50 000) to be properly assessed. The last electronic searches were last run on 11 March 2016.

PARTICIPANTS/MATERIALS, SETTING, METHOD

There were 12 observational studies encompassing 195 325 singleton pregnancies included in the study. No RCT reported the studied outcomes. The quality of the included studies was evaluated according to the Newcastle-Ottawa Scale and the quality of the evidence was evaluated according to GRADE criteria.

MAIN RESULTS AND THE ROLE OF CHANCE

Blastocyst stage transfer was associated with increased risks of preterm birth (<37 weeks), very preterm birth (<32 weeks), large for gestational age and perinatal mortality, although the latter was only identified from one study. Conversely, blastocyst stage transfer was associated with a decrease in the risks of small for gestational age and vanishing twins, although the latter was reported by only one study.

LIMITATIONS, REASONS FOR CAUTION

The observational nature of the included studies and some inconsistency and imprecision in the analysis contributed to decreasing our confidence in the estimates.

WIDER IMPLICATIONS OF THE FINDINGS

Due to the overall low quality of available evidence, the clinical equipoise between cleavage stage and blastocyst transfer remains. More large well-conducted studies are needed to clarify the potential risks and benefits of blastocyst transfer. As this review was initiated to support global recommendations on best practice, and in light of the challenges in lower resource settings to offer extended culture to blastocyst stage, it is critical to take into consideration these obstetric and neonatal outcomes in order to ensure any recommendation will not result in the overburdening of existing maternal and child health care systems and services.

STUDY FUNDING/COMPETING INTERESTS

No external funding was either sought or obtained for this study. The authors have no competing interests to declare.

PROSPERO REGISTRATION NUMBER

CRD42015023910.

Phenotypic developmental plasticity induced by preincubation egg storage in chicken embryos (Gallus gallus domesticus)

The developing chicken blastoderm can be temporarily maintained in dormancy below physiological zero temperature. However, prolonged preincubation egg storage impairs normal morphological and physiological development of embryos in a potential example of fetal programming (in this case, “embryonic programming”). We investigated how preincubation egg storage conditions (temperature, duration, hypoxia, and hypercapnia) affects viability, body mass, and physiological variables and functions in day 15 chicken embryos. Embryo viability was impaired in eggs stored for 2 and 3 weeks, with the effects greater at 22°C compared to 15°C. However, embryo size was reduced in eggs stored at 15°C compared with 22°C. Phenotypic change resulting from embryonic programming was evident in the fact that preincubation storage at 15°C diminished hematocrit (Hct), red blood cell concentration ([RBC]), and hemoglobin concentration ([Hb]). Storage duration at 15°C more severely affected the time course (2, 6, and 24 h) responses of Hct, [RBC], and [Hb] to progressive hypoxia and hypercapnia induced by submersion compared with storage duration at 22°C. The time‐specific regulation of acid–base balance was changed progressively with storage duration at both 22 and 15°C preincubation storages. Consequently, preincubation egg storage at 22°C resulted in poor viability compared with eggs stored at 15°C, but size and physiological functions of embryos in eggs stored for 1–2 weeks were worse in eggs stored in the cooler than stored under room conditions. Avian eggs thus prove to be useful for examining developmental consequences to physiology of altered preincubation thermal environment in very early stages of development (embryonic programming).

Blastocyst culture using single versus sequential media in clinical IVF: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

The purpose of this study was to undertake a review of the available evidence comparing the use of a single medium versus sequential media for embryo culture to the blastocyst stage in clinical IVF.

METHODS

We searched the Cochrane Central, PubMed, Scopus, ClinicalTrials.gov, Current Controlled Trials and WHO International Clinical Trials Registry Platform to identify randomized controlled trials comparing single versus sequential media for blastocyst culture and ongoing pregnancy rate. Included studies randomized either oocytes/zygotes or women. Eligible oocyte/zygote studies were analyzed to assess the risk difference (RD) and 95 % confidence intervals (CI) between the two media systems; eligible woman-based studies were analyzed to assess the risk ratio (RR) and 95 % CI for clinical pregnancy rate.

RESULTS

No differences were observed between single and sequential media for either ongoing pregnancy per randomized woman (relative risk (RR) = 0.9, 95 % CI = 0.7 to 1.3, two studies including 246 women, I ² = 0 %) or clinical pregnancy per randomized woman (RR = 1.0, 95 % CI = 0.7 to 1.4, one study including 100 women); or miscarriage per clinical pregnancy: RR = 1.3, 95 % CI = 0.4 to 4.3, two studies including 246 participants, I ² = 0 %). Single media use was associated with an increase blastocyst formation per randomized oocyte/zygote (relative distribution (RD) = +0.06, 95 % CI = +0.01 to +0.12, ten studies including 7455 oocytes/zygotes, I ² = 83 %) but not top/high blastocyst formation (RD = +0.05, 95 % CI = -0.01 to +0.11, five studies including 3879 oocytes/zygotes, I ² = 93 %). The overall quality of the evidence was very low for all these four outcomes.

CONCLUSIONS

Although using a single medium for extended culture has some practical advantages and blastocyst formation rates appear to be higher, there is insufficient evidence to recommend either sequential or single-step media as being superior for the culture of embryos to days 5/6. Future studies comparing these two media systems in well-designed trials should be performed.

Effect of mesenchymal stem cells and mouse embryonic fibroblasts on the development of preimplantation mouse embryos

Despite advances in assisted reproduction techniques, the poor quality and failures in embryo in vitro development remain as drawbacks resulting in low pregnancy rate. Mouse embryonic fibroblasts (MEFs) have been widely used to support embryonic stem cells. Mesenchymal cells (MSCs) have also been shown to release bioactive factors. In the present study, we have evaluated the ability of MSCs and MEFs to support early development of mouse embryos. The embryos were cultivated alone or in coculture with inactivated MSC or MEF for 4 d. After 4 d in culture, the percentage of blastocyst formation in coculture with MSC (91.7 ± 4.3%) or MEF (95.1 ± 3.3%) was higher than in the control group (72.2 ± 9.0%). We did not observe any difference in proliferation or apoptosis. However, the blastocysts cocultured with MSC or MEF presented a significantly higher number of cells within the inner cell mass per embryo when compared to the controls. The MSC and MEF groups presented also a higher cell number and diameter when compared to the control (CTRL). In summary, our data indicate that coculture with MSC or MEF improves early embryonic development and quality in vitro.

Do We Pay Enough Attention to Culture Conditions in Context of Perinatal Outcome after In Vitro Fertilization? Up-to-Date Literature Review

Adverse perinatal outcomes in singleton IVF pregnancies have been most often explained by parental underlying diseases and so far laboratory conditions during embryo culture are still not explored well. The following review discusses the current state of knowledge on the influence of IVF laboratory procedures on the possible perinatal outcome. The role of improved media for human embryo culture is unquestionable. Addition of certain components to culture media and their effect on embryo survival and implantation rates have been taken into consideration recently and studied on animal model. Impact of media on perinatal outcome in IVF offspring has also been studied. It has been discovered that epigenetic changes and neonatal birth weight are probably associated with the use of specific culture media, as is the relation between placental size and its influence on perinatal outcome. There are still questions in the discussion about duration of embryo culture (cleavage stage versus blastocyst transfer). Some of the IVF methods, such as in vitro maturation of oocytes and freezing/thawing procedures, also require well-powered randomized controlled trials in order to define their exact impact on perinatal outcome. Constant further research is needed to assess the impact of laboratory environment on fetal and postnatal development.

Should we be promoting embryo transfer at blastocyst stage?

Improved laboratory standards and better culture media have made extended culture to blastocyst stage a reality to identify embryos with maximum implantation potential. The strategy of extended culture has become more popular across the world at a time when regulatory bodies have emphasized the need to increase the uptake of elective single embryo transfer, minimize complications associated with multiple births and aim for a healthy singleton live-birth as the preferred outcome in IVF. New data on perinatal outcomes suggest that pregnancies after embryo transfer at blastocyst stage are associated with a higher risk of preterm delivery, large for gestational age babies, monozygotic twins and altered sex ratio compared with those following embryo transfers at cleavage stage. In addition, concerns have been raised of increased congenital anomalies and epigenetic modifications with embryo transfer at blastocyst stage. Twenty-four years on from the first embryo transfer at blastocyst stage, we examine the reasons for extended embryo culture, evaluate the risks and benefits of this strategy and suggest the need to reconsider this policy in the interests of fetal safety.

The effects of chemical and physical factors on mammalian embryo culture and their importance for the practice of assisted human reproduction

BACKGROUND

Although laboratory procedures, along with culture media formulations, have improved over the past two decades, the issue remains that human IVF is performed in vitro (literally 'in glass').

METHODS

Using PubMed, electronic searches were performed using keywords from a list of chemical and physical factors with no limits placed on time. Examples of keywords include oxygen, ammonium, volatile organics, temperature, pH, oil overlays and incubation volume/embryo density. Available clinical and scientific evidence surrounding physical and chemical factors have been assessed and presented here.

RESULTS AND CONCLUSIONS

Development of the embryo outside the body means that it is constantly exposed to stresses that it would not experience in vivo. Sources of stress on the human embryo include identified factors such as pH and temperature shifts, exposure to atmospheric (20%) oxygen and the build-up of toxins in the media due to the static nature of culture. However, there are other sources of stress not typically considered, such as the act of pipetting itself, or the release of organic compounds from the very tissue culture ware upon which the embryo develops. Further, when more than one stress is present in the laboratory, there is evidence that negative synergies can result, culminating in significant trauma to the developing embryo. It is evident that embryos are sensitive to both chemical and physical signals within their microenvironment, and that these factors play a significant role in influencing development and events post transfer. From the viewpoint of assisted human reproduction, a major concern with chemical and physical factors lies in their adverse effects on the viability of embryos, and their long-term effects on the fetus, even as a result of a relatively brief exposure. This review presents data on the adverse effects of chemical and physical factors on mammalian embryos and the importance of identifying, and thereby minimizing, them in the practice of human IVF. Hence, optimizing the in vitro environment involves far more than improving culture media formulations.