Dichorionic diamniotic twin pregnancy after preimplantation genetic testing and single blastocyst transfer

BACKGROUND

In addition to the potential for multiple pregnancies, natural conception occurring in preimplantation genetic testing (PGT) increases undesired genetic risk. Some studies showed that a dichorionic diamniotic twin pregnancy after a single blastocyst transfer could be caused by embryo splitting or concurrent spontaneous conception.

CASE

We describe a patient undergoing PGT who had a dichorionic diamniotic twin pregnancy after single blastocyst transfer in a natural cycle. In this case, we recommended to determine genetic status of the twins by prenatal diagnosis. The results showed that karyotype, chromosome copy number variation, and parental ACAT1 variation of the twins were all normal and similar. To investigate the origin of pregnancy, we used the genotype data of single-nucleotide polymorphisms typical of genome-wide association studies. Dizygotic twins were inferred by robust estimation of kinship coefficients, which confirmed the occurrence of a spontaneous conception.

CONCLUSIONS

This case strengthens the importance of genetic counseling to inform couples with reproductive genetic risk, such as those who undergo PGT, that intercourse should be avoided, especially in natural transfer cycles. Moreover, prenatal diagnosis remains essential and is strongly recommended to avoid genetic risks.

Maternal and perinatal risks for monozygotic twins conceived following frozen-thawed embryo transfer: a retrospective cohort study

BACKGROUND

The present study aimed to explore the maternal and perinatal risks in cases of monozygotic twins (MZT) following frozen-thawed embryo transfer (FET).

METHODS

All twin births that were conceived following FET from 2007 to 2021 at Shanghai Ninth People's Hospital in Shanghai, China were retrospectively reviewed. The exposure variable was twin type (monozygotic and dizygotic). The primary outcome was the incidence of neonatal death while secondary outcomes included hypertensive disorders of pregnancy, gestational diabetes, intrahepatic cholestasis of pregnancy, placenta previa, placental abruption, preterm premature rupture of the membranes, Cesarean delivery, gestational age, birth weight, weight discordance, stillbirth, birth defects, pneumonia, respiratory distress syndrome, necrotizing enterocolitis, and neonatal jaundice. Analysis of the outcomes was performed using logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals (CIs). The causal mediation analysis was conducted. A doubly robust estimation model was used to validate the results. Kaplan-Meier method was used to calculate survival probability. The sensitivity analysis was performed with a propensity score-based patient-matching model.

RESULTS

Of 6101 dizygotic twin (DZT) and 164 MZT births conceived by FET, MZT showed an increased risk of neonatal death based on the multivariate logistic regression models (partially adjusted OR: 4.19; 95% CI, 1.23-10.8; fully adjusted OR: 4.95; 95% CI, 1.41-13.2). Similar results were obtained with the doubly robust estimation. Comparing MZT with DZT, the neonatal survival probability was lower for MZT (P < 0.05). The results were robust in the sensitivity analysis. Females with MZT pregnancies exhibited an elevated risk of preterm premature rupture of the membranes (adjusted OR: 2.42; 95% CI, 1.54-3.70). MZT were also associated with higher odds of preterm birth (prior to 37 weeks) (adjusted OR: 2.31; 95% CI, 1.48-3.67), low birth weight (adjusted OR: 1.92; 95% CI, 1.27-2.93), and small for gestational age (adjusted OR: 2.18; 95% CI, 1.21-3.69) in the fully adjusted analyses. The effect of MZT on neonatal death was partially mediated by preterm birth and low birth weight (P < 0.05).

CONCLUSIONS

This study indicates that MZT conceived by FET are related to an increased risk of neonatal death, emphasizing a potential need for comprehensive antenatal surveillance in these at-risk pregnancies.

Multiple Gestation after Elective Single-Embryo Transfer: A State-of-the-Art Review of Literature and Suggested Mechanisms

Background

Elective single-embryo transfers are being increasingly used to curb the increase in multiple gestation rates. However, it has been documented that single-embryo transfers could still result in twins and on rarer occasions in triplet pregnancies. Main Body. A literature review was done to highlight the possible mechanisms leading to embryonic splitting. In this review, the incidence of zygotic splitting was addressed and the notion of chorionicity was explained. Risk factors for zygotic splitting and suggested mechanisms for both twin and higher order pregnancies were suggested and discussed.

Conclusion

The hypotheses that we have so far remain unproven due to the rarity of zygotic splitting as well as the ethicolegal considerations of human embryo research. The presence of such incidents necessitates extensive counselling of the couple.

Effect of blastocyst morphology on the incidence of monozygotic twinning pregnancy after single blastocyst transfer

Aims: To explore whether blastocyst morphology [blastocyst stage, inner cell mass (ICM), and trophectoderm (TE) grading] impacts the occurrence of monozygotic twinning (MZT) after single blastocyst transfer (SBT).Materials and methods: A single-center retrospective cohort study was conducted including all clinical pregnancies after single blastocyst transfer between January 2015 and September 2021 (n = 9229). Blastocyst morphology was assessed using Gardner grading system. MZT was defined as more than one gestational sac (GS), or two or more fetal heartbeats in a single GS via ultrasound at 5-6 gestational weeks.Results: The overall MZT rate was 2.46% (227 of 9229 cases), of which was the highest in blastocysts of grade A TE and lowest in those with grade C TE (grade A: B:C = 3.40%:2.67%:1.58%, p = .002). Higher risk of MZT pregnancy was associated with higher trophectoderm grading [A vs. C: aOR, 1.883, 95% CI 1.069-3.315, p = .028; B vs C: aOR, 1.559, 95% CI 1.066-2.279, p = .022], but not extended culture in vitro (day 5 vs. day 6), vitrification (fresh vs. frozen-thawed ET), assisted hatching (AH), blastocyst stage (stage 1-6) or ICM grading (A vs. B).Conclusions: We conclude that TE grade is an independent risk factor of MZT after single blastocyst transfer. Blastocysts with high-grade trophectoderm are more liable to obtain monozygotic multiple gestation.

The effect of the day 3 embryo cell number on the neonatal outcomes of day 5 single blastocyst transfer in frozen embryo transfer cycles

OBJECTIVE

To evaluate the influence of the day 3 embryo cell number on the neonatal outcomes of day 5 single blastocyst transfer in frozen embryo transfer (FET) cycles.

METHODS

This retrospective study analysed a total of 2315 delivery cycles of day 5 single blastocyst transfer in FET cycles, including 489, 761 and 1103 live-born infants segregated according to a day 3 embryo cell number of <8, 8 and >8 cells, respectively. The neonatal outcomes of the three groups were compared.

RESULTS

The day 3 embryo cell number did not significantly affect the incidence of monozygotic twins. The sex ratio increased as the day 3 embryo cell number increased, but the difference was not statistically significant. There were no significant differences in the rates of preterm birth or low birth weight among the three groups. The rates of stillbirths and neonatal deaths were also not significantly different among the three groups. Moreover, the day 3 embryo cell number did not increase the risk of birth defects in newborns.

CONCLUSIONS

The day 3 embryo cell number did not significantly affect neonatal outcomes.

Recurrence risk and risk factors for monozygotic twin and triplet birth in over 65,000 single-embryo transfers

PURPOSE

To determine the recurrence risk and risk factors for monozygotic splitting after elective single-embryo transfers (eSET).

METHODS

A retrospective cohort study was performed investigating 65,664 eSET cycles that resulted in a clinical pregnancy as reported in the Society for Assisted Reproductive Technology (SART) Clinical Outcomes Reporting System (CORS) between 2004 and 2017. Monozygosity was defined as more than one fetal heart tone by the first-trimester ultrasound and concordant sex at live birth. The primary outcome was recurrence risk, with recurrence defined as one patient having two or more cycles of eSET resulting in monozygotic multiples. The secondary objective was to identify factors associated with smonozygotic splitting, using a multivariable logistic regression model and a stepwise purposeful model selection.

RESULTS

There were 1355 (2.05%) pregnancies that resulted in two or more fetal heart tones after SET, including 840 monozygotic twins and triplets at birth. Recurrence occurred in two cases-0.0001% of patients with multiple eSET cycles. One case resulted from embryos created from a single cohort with intracytoplasmic sperm injection (ICSI), assisted hatching (AH), and blastocyst transfers. The second case resulted from donor egg embryos with ICSI and blastocyst transfers. Risk factors associated with monozygotic live birth were blastocyst transfer (OR 1.23, 95% CI 1.04-1.47, P = 0.0176) and AH (OR 1.23, 95% CI 1.05-1.44, P = 0.0081).

CONCLUSION

Recurrence of monozygotic live births in eSET was very rare. Blastocyst transfer and AH were confirmed to be risk factors for monozygotic live births, while ICSI, PGT, and FET do not appear to be associated.

Molecular Characterization of a Rare Case of Monozygotic Dichorionic Diamniotic Twin Pregnancy after Single Blastocyst Transfer in Preimplantation Genetic Testing (PGT)

Preimplantation genetic testing (PGT) is widely used to select unaffected embryos, increasing the odds of having a healthy baby. During the last few decades, it was accepted that monozygotic dichorionic diamniotic twin pregnancies occurred from the embryo splitting before Day 3 postfertilization according to Corner’s dogma. Hence, the occurrence of a dichorionic diamniotic twin pregnancy after a single blastocyst transfer was considered a dizygotic pregnancy resulting from blastocyst transfer and concurrent natural fertilization. In our study, we have provided for the first time molecular proof that a single blastocyst transfer can result in a monozygotic dichorionic diamniotic twin pregnancy, invalidating Corner’s dogma. In this case, we recommend systematically assessing the genetic status of dichorionic twins after single blastocyst transfer using prenatal diagnosis to exclude the risk from a potential concurrent spontaneous pregnancy and to ensure that both fetuses are unaffected. To achieve this goal, we have developed here an innovative noninvasive prenatal diagnosis by exclusion of paternal variants with droplet digital PCR, maximizing the reliability of genetic diagnosis. Further multicentric prospective studies using genetic testing are now required to establish the rate of blastocyst splitting leading to dichorionic pregnancy in PGT and to identify the risk factors.

Pregnancy Outcomes Following the First Frozen Blastocyst Transfer Among Women Aged Less Than 35 Years Old: A Retrospective Cohort Study

Background: Many guidelines have been issued regarding the number of embryos to be transferred after in vitro fertilization (IVF), but patients and clinicians may be reluctant to accept or offer a single embryo transfer due to the expected lower chance of pregnancy or live birth. This study was aimed to provide additional information on cycle outcome according to the number and quality of thawed transferred blastocysts.

Methods: A retrospective cohort study was designed to collect the data of 505 patients who performed the first frozen blastocysts transfer at Tam Anh General Hospital from June 2018 to September 2019. One good-quality embryo was transferred for 121 patients (Group 1), two good for 214 patients (Group 2), one good and one poor for 112 patients (Group 3), one good and two poor for 25 patients (Group 4), and one or two poor for 33 patients (Group 5).

Results: The pregnancy rate was 71.9%, 74.8%, 69.4%, 84.0%, and 39.4% in Group 1–5, respectively. The multiple pregnancy rate was 36.9%, 16.9%, and 32.0% in Groups 2–4, respectively, higher than Group 1 (4.9%). The live birth rate was 55.6%, 50.9%, and 60.0% in Group 2–4, respectively, but not significantly different from the Group 1 (47.9%).

Conclusions: Transferring an additional good or poor embryo, along with a good embryo, does not increase the live birth rate while the incidence of multiple pregnancies rises significantly.

On the origin of zygosity and chorionicity in twinning: evidence from human in vitro fertilization

Assisted reproduction is presumed to increase monozygotic twin rates, with the possible contribution of laboratory and medical interventions. Monozygotic dichorionic gestations are supposed to originate from the splitting of an embryo during the first four days of development, before blastocyst formation. Single embryo transfers could result in dichorionic pregnancies, currently explained by embryo splitting as described in the worldwide used medical textbooks, or concomitant conception. However, such splitting has never been observed in human in vitro fertilization, and downregulated frozen cycles could also produce multiple gestations. Several models of the possible origins of dichorionicity have been suggested. However, some possible underlying mechanisms observed from assisted reproduction seem to have been overlooked. In this review, we aimed to document the current knowledge, criticize the accepted dogma, and propose new insights into the origin of zygosity and chorionicity.

Monozygotic dichorionic-diamniotic pregnancies following single frozen-thawed blastocyst transfer: a retrospective case series

BACKGROUND

The primary aim of the study is to report cases of monozygotic dichorionic-diamniotic (DC-DA) pregnancies after single frozen-thawed blastocyst transfer.

METHODS

This is a retrospective case series. All single frozen-thawed blastocyst transfer cycles performed between June 2013 and December 2018 at the Shanghai Ji Ai Genetics and IVF Institute, Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China, were reviewed retrospectively. We included frozen embryo transfer (FET) cycles which clinical pregnancy was confirmed with multiple gestational sacs showed on ultrasonography at around 6 to 7 weeks of gestation. We then conducted an in-depth analysis to further exclude cases which contained newborns of different genders or natural FET cycles.

RESULTS

Five thousand four hundred fifteen frozen-thawed single blastocyst transfer cycles were preformed between June 2013 and December 2018 at the Shanghai Ji Ai Genetics and IVF Institute, Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China. Of these, fourteen women underwent a single blastocyst transfer and then achieved clinical pregnancy with an ultrasound diagnosis of multi-chorionic pregnancy. With one natural cycle FET excluded, we finally included thirteen single blastocyst transfer cycles performed in down-regulated controlled FET or hormone replacement FET, in which the possibility of concurrently spontaneous pregnancy was extremely small. These included 13 cases reveal the phenomenon of monozygotic DC-DA twinning after single blastocyst transfer, which challenges the classical theory that only monochorionic pregnancy could happen after 3 days of fertilization.

CONCLUSION

This case series suggest that single blastocyst transfer could result DC-DA pregnancies during IVF treatment.

Risk Factors for Monozygotic Twins in IVF-ICSI Cycles: a Case-Control Study

In vitro fertilization (IVF) is associated with a higher incidence of monozygotic twin pregnancies, which are known to be burdened by a higher risk of main obstetric complications. The reasons behind this association are still unclear. In the present study, we therefore investigate the risk factors for monozygotic twinning in pregnancies achieved by IVF. We conducted a multicenter retrospective case-control study. All IVF cycles performed between 2014 and 2019 at the infertility units of two Italian academic institutes were retrospectively reviewed. Only pregnancies obtained with single embryo transfer were eligible. A total of 50 monozygotic twin pregnancies (cases) were identified and matched in a 1:5 ratio to 250 singleton pregnancies (controls) by study center and study period. Monozygotic twin pregnancies were diagnosed by ultrasound. Women experiencing miscarriage could be included provided that the pregnancy loss occurred after a definitive diagnosis of monozygotic twin pregnancy. Demographic, clinical, and embryological characteristics were retrieved from patients' charts. Overall, the incidence of monozygotic twin pregnancies was 1.2% (50 out of 4016 single embryo transfers). At univariate analyses, statistically significant differences emerged for BMI, peripheral levels of estradiol and progesterone at the time of hCG administration, total number of retrieved suitable oocytes, freezing-thawing cycles, and assisted hatching. After performing a multivariate logistic analysis, only assisted hatching remained significantly associated with monozygotic twinning (adjusted odds ratio 2.32, 95%CI 1.03-5.25). Blastomere separation during the passage through this artificial hole or interference with the signaling pathway within the embryo could be the mechanisms involved.

Assisted hatching of vitrified-warmed blastocysts prior to embryo transfer does not improve pregnancy outcomes

Objective

This study aims to determine the impact of assisted hatching (AH) on pregnancy outcomes in vitrified-warmed blastocyst transfers, and evaluate if embryo expansion or morphology influences outcomes.

Methods

A retrospective cohort study was performed including vitrified-warmed blastocyst transfers at our clinic between 2013 and 2017. Of the 2165 embryo transfers, 1986 underwent laser AH and 179 were non-assisted hatched (NAH). The primary outcome was live birth. Secondary outcomes included conception, implantation, clinical pregnancy, clinical pregnancy loss, and monozygotic twinning (MZT).

Results

AH and NAH groups had similar rates of conception (38.7% vs 42.1%), implantation (26.2% vs 27.3%), clinical pregnancy (29.1% vs 30.3%), clinical pregnancy loss (24.0% vs 17.8%), live birth (19.9% vs 20.5%), and MZT (2.08% vs 2.86%). Five pairs of dichorionic/diamniotic twins resulted from single embryo transfers. AH of embryos with expansion grades ≤3 was associated with lower rates of conception (32.5% vs 44.3%%, p < 0.05) and clinical pregnancy (24.0% vs 32.8%, p < 0.05).

Conclusion

AH prior to transfer of vitrified-warmed blastocysts was not associated with improved pregnancy outcomes. The identification of dichorionic/diamniotic twins from single blastocyst transfers challenges the previously held notion that dichorionic/diamniotic MZTs can only occur from division prior to the blastocyst stage. Prospective studies are needed to validate the novel finding of lower rates of conception and clinical pregnancy after AH in embryos with lower expansion grade.

The indicator of clinical outcomes for patients with heterotopic pregnancy following in-vitro fertilization with embryo transfer

OBJECTIVE

To explore the early predictors for pregnancy outcomes in patients with heterotopic pregnancy (HP) following in-vitro fertilization with embryo transfer (IVF-ET).

MATERIAL AND METHODS

This retrospective study reviewed 81 patients with HP following IVF-ET in our institution between January 2003 and September 2017. The relationships between clinical outcomes and general characteristics, sonographic features and different management options were analyzed by logistic regression analysis.

RESULTS

The gestational age at the time of diagnosis was 50.9 ± 12.3 days. Among these cases, 76 were accurately diagnosed by TVS, 1 was misdiagnosed as adnexal torsion by TVS, and 4 were confirmed to have IUPs after the surgical treatment. Hence, the sensitivity of TVS for detecting HP was 93.8% (76/81). However, forty-seven patients (58.0%) had suspected HP when they underwent the initial TVS. Among these patients, live births occurred for 60 patients, 11 of whom delivered preterm. The miscarriage rate was 58.3% (14/24) for patients without IUP cardiac activity at HP diagnosis, and 12.3% (7/57) for patients with IUP cardiac activity; a significant correlation was identified (χ² = 18.651, P < 0.001). Additionally, the abortion rate of patients following fresh non-donor embryo was higher than patients after frozen-thawed embryo (χ² = 10.437, P = 0.001). Further by logistic regression analysis, patients following frozen-thawed embryo and an IUP with cardiac activity at HP diagnosis were identified as two independent factors of pregnancy outcome. (OR = 0.060, 95%CI = 0.008-0.471, P = 0.007; OR = 0.010, 95%CI = 0.001-0.124, P<0.001).

CONCLUSIONS

Patients following frozen-thawed embryo and an IUP with cardiac activity at HP diagnosis could be the independent predictors for a favorable prognosis.

Monoamniotic twin pregnancy following the transfer of a single blastocyst resulting from intracytoplasmic sperm injection of a single oocyte: a case report

In this report we present an unusual case of a couple who achieved a twin pregnancy by intracytoplasmic sperm injection (ICSI) with a single immature oocyte retrieved. The oocyte was at metaphase I at 39 h post human chorionic gonadotrophin (hCG) administration, which is our standard ICSI time. Extended culture allowed the extrusion of the polar body, and sperm injection was performed at 43 h post-trigger. The fertilized egg underwent embryo biopsy on day 3 and preimplantation genetic assessment for three chromosomes (X, Y and 21). The embryo remained in culture until day 5. Later, the biopsy results reported a transferable embryo, which was replaced to the uterine cavity at blastocyst stage. Pregnancy test gave a positive β-hCG result, and the 6 weeks' scan, performed to confirm the fetal heart, revealed the presence of one amniotic sac and two fetal heartbeats, which currently have been so far eventless and smooth, ongoing at 18 weeks of gestation.

Successful monozygotic triplet pregnancy after a single blastocyst transfer following in vitro maturation of oocytes from a woman with polycystic ovary syndrome: a case report

Background

Although women with polycystic ovarian syndrome (PCOS)-related sub-fertility are high responders to controlled ovarian stimulation, it is difficult to obtain mature oocytes in these women. Therefore, in vitro maturation (IVM), which is the technique of letting the contents of the ovarian follicles and the oocytes inside mature in vitro, has often been proposed in such women. We describe the first successful delivery of monozygotic triplets resulting from transfer of a single blastocyst following IVM of oocytes.

Case presentation

A 32-year-old nulligravida female with PCOS underwent IVM. She underwent vitrified-warmed single blastocyst transfer following IVM, and a dichorionic triamniotic triplet pregnancy was confirmed at 8 weeks. Healthy triplets were delivered by cesarean section at 33 weeks’ gestation. This is the first case of monozygotic triplets derived from IVM oocytes that were successfully delivered. The determination of chorionicity and amnionicity is generally supposed until 3 days after fertilization, and no division or splitting of her embryo was observed on transfer. Interestingly, her embryo might have split after the transfer, resulting in a dichorionic triamniotic triplet pregnancy.

Conclusions

Patients should be informed of a possible increased risk of monozygotic multiple pregnancies after single embryo transfer following IVM.

Risk factors for monozygotic twinning after in vitro fertilization: a systematic review and meta-analysis

OBJECTIVES

To establish the risk factors for monozygotic twin (MZT) and monochorionic twin (MCT) pregnancies after in vitro fertilization (IVF).

DESIGN

Systematic review and meta-analysis.

SETTING

Not applicable.

PATIENT(S)

Women who achieved MZT and non-MZT pregnancies through IVF.

INTERVENTION(S)

Systematic search of Medline from January 1995 to October 2018 with cross-checking of references from relevant articles in English.

MAIN OUTCOME MEASURE(S)

Possible risk factors for MZT or MCT pregnancies after IVF, comprising extended embryo culture, insemination method (conventional IVF and intracytoplasmic sperm injection [ICSI]), embryo biopsy for preimplantation genetic testing for aneuploidies or for monogenic/single-gene defects (PGT-A or PGT-M) programs, assisted hatching (AH), oocytes donation, female age, and embryo cryopreservation.

RESULT(S)

A total of 40 studies were included. Blastocyst transfer compared with cleavage-stage embryo transfer, and female age <35 years were associated with a statistically significant increase in the MZT and MCT pregnancy rate after IVF: (23 studies, OR 2.16, 95% CI, 1.74-2.68, I²=78%; 4 studies, OR 1.29; 95% CI, 1.03-1.62, I²=62%; and 3 studies, OR 1.90, 95% CI, 1.21-2.98, I²=59%; 2 studies, OR 2.34; 95% CI, 1.69-3.23, I²=0, respectively). Conventional IVF compared with ICSI and assisted hatching were associated with a statistically significantly increased risk of MZT pregnancy (9 studies, OR 1.19, 95% CI, 1.04-1.35, I²=0; 16 studies, OR 1.17, 95% CI, 1.09-1.27, I²=29%, respectively). Embryo biopsy for PGT-A or PGT-M, embryo cryopreservation, and oocytes donation were not associated with MZT pregnancies after IVF.

CONCLUSION(S)

Blastocyst transfer is associated with an increased risk of both MZT and MCT pregnancies after IVF. Further evidence is needed to clarify the impact of female age, insemination method and AH on the investigated outcomes.

Determinants of monozygotic twinning in ART: a systematic review and a meta-analysis

BACKGROUND

The incidence of monozygotic twins (MZT) after ART appears to be higher than the incidence after spontaneous conceptions contradicting the aim of ART to avoid multiple pregnancies because of the associated risks.

OBJECTIVE AND RATIONALE

The aim was to study the frequency of MZT after IVF and ICSI and how it is influenced by the day of embryo transfer, maternal age, zona pellucida manipulation, controlled ovarian stimulation, stimulation protocol, culture media and embryo quality.

SEARCH METHODS

Original studies and reviews were identified by searching the PubMed, Embase and Cochrane databases up to March 2017. The inclusion criterion was publications focusing on the five study questions related to MZT in our study. The exclusion criteria were articles that did not include blastocyst transfer, were on non-humans, were not published in peer-reviewed journals, and were based only on case studies. All of the articles were categorized according to the Oxford Centre for Evidence-based Medicine's 'Levels of Evidence', and quality and risk of bias assessment was performed with 'The Cochrane Collaboration's Risk of Bias Tools'. A meta-analysis was performed to study the impact of the day of embryo transfer on the MZT rate.

OUTCOMES

The literature search resulted in a total of 42 articles, including 38 original studies, for analysis. The included original studies reported a MZT rate with blastocyst transfer from zero to 13.2%. Our meta-analysis found a higher frequency of MZT after blastocyst transfer compared with cleavage-stage embryos transfer: odds ratio = 2.18, 95% CI: 1.93-2.48 (fixed effect meta-analysis). A younger maternal age may increase the MZT rate, and recent studies regarding the use of zona pellucida manipulating techniques have disagreed with the previous suspicion of a higher MZT rate after the use of these methods. The extended culture to-blastocyst stage is a potential risk factor for MZT, but it is uncertain whether this phenomenon is due to the extended time, culture media or greater likelihood of younger oocytes to reach the blastocyst stage. An increased frequency of MZT following the GnRH-agonist suppression protocol has been suggested, as well as a decreased frequency of MZT with high gonadotrophin doses, which could reflect an age-related effect. Only limited literature has focused on the role of embryo morphology in the MZT rate, therefore, this issue remains unresolved.

WIDER IMPLICATIONS

We found blastocyst transfer to be a risk factor for MZT. Hence, the results of this meta-analysis may weaken the previously proposed view that greater experience with blastocyst transfer and improved culture media could decrease the high rate of MZT after blastocyst transfer. To minimize the rate of MZT and the associated complications, the mechanisms underlying blastocyst transfer and MZT pregnancy must be elucidated.

Multi-chorionic pregnancies following single embryo transfer at the blastocyst stage: a case series and review of the literature

OBJECTIVE

To report cases of in vitro fertilization-frozen embryo transfer (IVF-FET) with single blastocyst transfer resulting in di- or tri-chorionic pregnancies, and to review the literature on monozygotic, multi-chorionic pregnancies originating at the blastocyst stage.

DESIGN

Retrospective case series and literature review.

MATERIALS AND METHODS

All in vitro fertilization cycles (fresh, frozen, autologous, and donor oocyte) performed between June 2012 and June 2017 at the University of California, San Francisco Center for Reproductive Health, were reviewed retrospectively. Cycles with cleavage-stage embryos or transfer of more than one blastocyst were excluded. Cycles were analyzed to determine if clinical pregnancy occurred with the presence of two or more gestational sacs noted on initial ultrasound. An in-depth chart review was performed with further exclusions applied that would lend credence to dizygosity rather than monozygosity such as fetal/neonatal sex discordance, fresh embryo transfer, and natural cycle FET (in which concomitant spontaneous pregnancy could have occurred). Demographic, clinical and IVF-FET cycle characteristics of the resulting patients were collected. Additionally, a review of the English language literature was performed (PUBMED, PMC) using the search words monozygotic twins, dichorionic diamniotic, in vitro fertilization, and single embryo transfer in order to identify cases of DC-DA monozygotic twinning from 1978 to 2017. Resulting articles were reviewed to eliminate all cases of dizygosity and day 3 embryo transfers. We obtained the following data from the literature search: basic patient demographics, type of fertilization, type and day of embryo transferred, number of embryos transferred, gestational ultrasound details, presence of any genetic testing if performed after delivery, and number of live births.

RESULT(S)

Two thousand four hundred thirty-four women underwent fresh or frozen single embryo transfer between June 2012 and June 2017 at the University of California, San Francisco Center for Reproductive Health. Of these, 11 women underwent a single blastocyst transfer with subsequent clinical pregnancies identified as multi-chorionic gestations. Four were in downregulated controlled FET cycles, in which concomitant spontaneous pregnancy could not have been possible. We then reviewed all cases of monozygotic dichorionic-diamniotic (DC-DA) splitting in IVF patients reported in the literature from 1978 to 2017. These eight cases demonstrate monozygotic splitting after the blastocyst stage, which challenges the existing dogma that only monochorionic twins can develop after day 3 post-fertilization.

CONCLUSION(S)

The accepted theory of monozygotic twinning resulting from the splitting of an embryo per a strict post-fertilization timing protocol must be re-examined with the advent of observed multi-chorionic pregnancies resulting from single blastocyst transfer in the context of IVF.

Effect of different artificial shrinkage methods, when applied before blastocyst vitrification, on perinatal outcomes

BACKGROUND

In recent years, single blastocyst transfer combined with vitrification has been applied widely, which can maximize the cumulative pregnancy rate in per oocyte retrieval cycles and minimize the multiple pregnancy rate. Thus, the guarantee for these is the effectiveness of vitrified blastocyst. Studies has shown that AS of the blastocoel cavity prior to vitrification can reduce injuries, increase the thawed blastocyst survival rate and implantation rate. Several AS methods have been established. However, only a few studies have compared the effectiveness and safety of these AS methods. In this study, we aimed to compare the clinical outcomes and neonatal outcomes in FET cycles with single blastocyst that were artificially shrunk before vitrification by either LAS or MNAS method.

METHODS

A retrospective comparative study of FET cycles in infertile patients which were at our clinic between January 2013 and December 2014. These FET cycles were divided into two groups by the shrinking methods used before vitrification and the clinical and neonatal outcomes were assessed.

RESULTS

There were no statistically differences in blastocyst survival rates (95.40% vs 94.05%, P > 0.05) between the LAS and MNAS groups. However, compared with MNAS, LAS improved the warmed blastocyst implantation/clinical pregnancy rate (60.82% vs 54.37%, P < 0.05), live birth rate (50.43% vs 45.22%, P < 0.05) and also increased the monozygotic twin rate (4.07% vs 1.73%, P < 0.05). There were no differences in the average gestational weeks (38.83 ± 1.57 vs 38.74 ± 1.75), premature birth rate (0.30% vs 0.49%), average birth weight (3217.89 ± 489.98 g vs 3150.88 ± 524.03 g), low birth weight rate (5.60% vs 8.63%) and malformation rate (0.59% vs 0.48%) (P > 0.05).

CONCLUSIONS

No significant differences in neonatal outcomes were observed, while in clinical outcomes, LAS improved the warmed blastocyst implantation/clinical pregnancy rate and live birth rate markedly, there was also an increased risk of monozygotic twin pregnancies.

Potential of zygotes to produce live births can be identified by the size of the male and female pronuclei just before their membranes break down

Aim

To determine whether there are differences in size between the male and female pronuclei immediately before the pronuclear membrane breakdown (PNMBD) and to evaluate whether pronuclear size differences influence normal birth rates.

Methods

Time‐lapse photography was used to measure the size of each pronucleus, while the outcome of 71 frozen‐thawed single blastocyst transfers in patients receiving hormone therapy was analyzed retrospectively. The pronuclear measurements were made 4 hours before the PNMBD, corresponding to 16‐20 hours after insemination or intracytoplasmic sperm injection, and immediately before the PNMBD. The differences in the areas between the pronuclei in the zygotes that were associated with the live births were compared with those that were associated with the failed pregnancies.

Results

The average difference in the area between the pronuclei 4 hours before and immediately before the PNMBD in the patients with a live birth was significantly smaller than in the patients with a failed birth. In addition, the average area difference in the patients with a successful birth was significantly smaller when the measurements were made immediately before the PNMBD, compared with the measurements 4 hours before the PNMBD. Such differences were not detected among the patients who did not achieve a birth.

Conclusion

The birth of healthy babies resulted from zygotes that contained pronuclei of similar size when the measurements were made immediately before the PNMBD. Evaluating the size of each pronucleus immediately before the PNMBD provides an effective indicator of the embryo's potential at an early stage of development.

Do ARTs affect the incidence of monozygotic twinning?

STUDY QUESTION

Does the manipulation of gametes or embryos during ARTs increase the risk for monozygotic twinning (MZT)?

SUMMARY ANSWER

Frozen embryo transfer (ET) is associated with a lower MZT rate, while blastocyst culture is associated with an increased risk of monozygotic pregnancy.

WHAT IS KNOWN ALREADY

Monozygotic twins have a higher risk for perinatal complications. Although an increased incidence of monozygotic pregnancies after ART has been previously reported, data regarding the possible impact of different laboratory procedures are conflicting.

STUDY DESIGN, SIZE, DURATION

All clinical pregnancies after single ET carried out in our centre between 2004 and 2013 (n = 6096) were retrospectively analysed for the incidence of MZT. The effect of different laboratory procedures on the incidence of MZT was evaluated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The following ART risk factors were assessed: maternal age, type of ET (fresh versus frozen), zona pellucida (ZP) manipulation (specifically, ICSI, embryo biopsy and assisted hatching), use of donor oocytes, embryo stage at time of ET (cleavage, compaction, early or advanced blastocyst) and culture media.

MAIN RESULTS AND THE ROLE OF CHANCE

The overall MZT rate was 2.2% (136/6096). Frozen ET was associated with a significant reduction in MZT incidence (adjusted odds ratio (aOR) 0.48, 95% CI 0.29-0.80), while blastocyst transfer (early or advanced blastocyst) was associated with a significant increase in MZT risk (aOR 2.70, 95% CI 1.36-5.34; aOR 2.05, 95% CI 1.29-3.26, respectively). No significant differences were found between the MZT and singleton (non-MZT) groups regarding maternal age, the use of different ZP manipulation techniques, not type of culture media used.

LIMITATION, REASONS FOR CAUTION

This study is limited by its retrospective nature and the fact that monozygosity was not confirmed by genetic testing. Furthermore, since monozygotic pregnancy is a rare event, other ART parameters that may influence its incidence could not be assessed during our analysis.

WIDER IMPLICATION OF THE FINDINGS

Our findings warrant future studies designed to investigate the association between specific ART procedures and MZT, namely the potential risk of blastocyst transfer to increase MZT.

STUDY FUNDING/COMPETING INTERESTS

No external funding was used for this study. There are no conflicts of interest.

45,X product of conception after preimplantation genetic diagnosis and euploid embryo transfer: evidence of a spontaneous conception confirmed by DNA fingerprinting

BACKGROUND

Preimplantation genetic screening (PGS) provides an opportunity to eliminate a potential implantation failure due to aneuploidy in infertile couples. Some studies clearly show that twins following single embryo transfer (SET) can be the result of a concurrent natural conception and an incidence as high as 1 in 5 twins has been reported. In our case PGS was performed on trophectoderm (TE) biopsies by quantitative polymerase chain reaction (qPCR). The product of conception (POC) was cytogenetically investigated after selection of the placental villi by means of the direct method. Molecular cytogenetic characterization of the POC was performed by fluorescence in situ hybridization (FISH) and array-comparative genomic hybridization (a-CGH) analyses. To investigate the possibility of a spontaneous conception, a panel of 40 single nucleotide polymorphisms (SNPs) was used to compare genetic similarity between the DNA of the POC and the DNA leftover of the TE biopsy.

FINDINGS

We describe a 36-year old infertile woman undergoing PGS who had a spontaneous abortion after a single euploid embryo transfer on a spontaneous cycle. The POC showed a 45,X karyotype confirmed by FISH and a-CGH. DNA fingerprinting demonstrated a genetic similarity of 75 % between the DNA of the POC and TE biopsy, consistent with a sibling status. All supernumerary euploid embryos were also tested showing a non-self relationship with the POC, excluding a mix-up event at the time of fetal embryo transfer.

CONCLUSIONS

DNA fingerprinting of the transferred blastocyst and POC, confirmed the occurrence of a spontaneous conception. This case challenges the assumption that a pregnancy after assisted reproductive technology (ART) is always a result of ART, and strengthens the importance to avoid intercourses during PGS and natural transfer cycles. Moreover, cytogenetic analysis of the POCs is strongly recommended along with fingerprinting children born after PGS to see what the concordance is between the embryo transferred and the resultant child.

Heterotopic pregnancy after a single embryo transfer

Heterotopic pregnancy is a rare and life-threatening condition which is defined as coexistent intrauterine and ectopic gestation. The risk of ectopic and heterotopic pregnancy is increasing due to the increased risk of multiple pregnancies with the aid of assisted reproductive technologies. However, it hardly happens in the setting of single embryo transfer, since single embryo transfer significantly reduces the incidence of multiple pregnancies. Surprisingly, we experienced a case of heterotopic pregnancy after a single embryo transfer caused by coincidental natural pregnancy during assisted reproductive technologies. An infertile woman who underwent, during her natural cycle, transfer of a single embryo that had been cryopreserved for 3 years was found to be heterotopically pregnant. After an early and successful management with laparoscopic right salpingectomy, she finally reached at full-term vaginal delivery.

Time-lapse monitoring reveals that vitrification increases the frequency of contraction during the pre-hatching stage in mouse embryos

Contraction during the blastocyst stage is observed during embryonic development of various mammals, including humans, but the physiological role of this process is not well understood. Using time-lapse monitoring (TLM), we studied the influence of vitrification and contractions on embryonic development in mice. Mouse embryos were cultured at the 2-cell stage. At the 8-cell stage, embryos were randomly divided into a fresh group (FG) and vitrified group (VG) and observed for up to 144 h. Strong contractions (i.e., contractions causing a decrease in volume of more than 20% and expansion of the perivitelline space) occurred significantly more often in unhatched embryos than hatching embryos in both groups. Regarding hatching embryos, contractions in the pre-hatching stage were significantly more frequent in the VG than the FG. Furthermore, mRNA expression levels of genes related to contractions were determined at three time points, the 8-cell stage, early blastocyst stage, and 20 h after blastocoel formation, with quantitative reverse transcription-polymerase chain reaction. There was no significant difference in Hspa1a expression between the FG and VG, but Hspa1a overexpression was observed just after thawing and tended to decrease gradually thereafter in some blastocysts. Furthermore, in the VG, Atp1a1 tended to show higher expression in the strong contraction group than in the weak contraction group. Overall, vitrification is an excellent method for cryopreservation but could increase contractions in the pre-hatching stage and may increase energy demands of the embryo. Observation of contraction by TLM may improve the evaluation of embryo quality.

Risk of Monozygotic Twins After Assisted Reproduction: A Population-Based Approach

BACKGROUND

Recent studies have suggested that ovarian stimulation and assisted reproductive techniques (ART) may increase the frequency of monozygotic twins. In this article, we present the analysis of the estimated frequency of twin deliveries following in vitro fertilization (IVF) in Lombardy during the period 2010-2014 for a total of 450,949 pregnancies.

METHOD

This is a population-based study using data from the regional data base of Lombardy, a northern Italian region with a population of about 10 million inhabitants. During the considered period, a total of 461,424 single or multiple births were registered in Lombardy. After exclusion of triplets or more pregnancies, the total number of twin deliveries, in separate strata of like and unlike sex pregnancies twin deliveries, were obtained and the rate of twin deliveries was computed according to spontaneous and non-spontaneous conception and type of ART. Further, estimates of dizygotic or monozygotic twin births were calculated using Weinberg's methods.

RESULTS

The frequency of twins deliveries was 1.24/100 deliveries after natural conception and 20.05 after assisted conception. The estimated rates of monozygotic twins was 0.45 and 0.72/100 (95% CI: 0.58-0.91) deliveries after natural and assisted conception, respectively. This difference was statistically significant (p < .05).

CONCLUSION

the present population based study suggests that the risk of monozygotic twin is about 60% higher among assisted than after natural conception.

Estimating the Risk of Monochorionic Twins in IVF Pregnancies From the Perspective of a Prenatal Diagnosis Unit

The aim of the present work was to estimate the risk of monochorionic twin (MCT) pregnancies in in vitro fertilization (IVF) cycles using data from a prenatal diagnosis unit. This was a retrospective cross-sectional study reporting on the frequency of IVF pregnancies among women attending a prenatal diagnosis service specifically dedicated to the management of monochorionic pregnancies. The observed rate was compared with the local regional rate of IVF births (2.2%). A binomial distribution model was used to calculate the 95% CI of proportions. One hundred and forty-five monochorionic pregnancies were selected. Ten of these were achieved with IVF, corresponding to a rate of 6.9% (95% CI: 3.5–11.8), significantly higher than the background rate in the local population of 2.2%. When considering exclusively monochorionic pregnancies achieving delivery of two viable newborns (n = 132), the number of IVF pregnancies was nine (6.8%, 95% CI: 3.7–12.5). We did not detect major differences in pregnancy outcome between IVF and natural monochorionic pregnancies, with the exception of the proportion of newborns with a neonatal birth < 2,500 g (100% vs. 80%, p = .03). In conclusion, data obtained from the perspective of a prenatal diagnosis unit suggest that women undergoing IVF face a 3- to 4-fold increased risk of monochorionic pregnancies.

Clustering of monozygotic twinning in IVF

PURPOSE

The aim of this analysis was to study whether monozygotic twinning (MZT) events occur in clusters after IVF and, if so, to explore possible explanations for this clustering.

METHODS

This is a retrospective cohort study carried out in a single, large university-affiliated reproductive medicine practice. Medical records of all patients who had undergone fresh IVF cycles, resulting in a viable clinical pregnancy, from Jan 2002 to Dec 2013 were reviewed. The incidence of MZT in 6-month intervals and the association with independent risk factors such as maternal age, extended embryo culture, PGD/intracytoplasmic sperm injection (ICSI)/assisted hatching performed were analyzed.

RESULTS

Over the 12-year study period, 25,502 fresh IVF cycles were performed, resulting in 8598 clinical pregnancies. Ninety-five cycles (1.1 %) resulted in MZ twins. The percentage of MZT was >2 standard deviations (SD) higher than the overall percentage of MZT in 4 of the 24 6-month intervals. PGD, extended embryo culture (≥4 days), and more recent cycles (2005 or later) were independent risk factors for MZT. The use of multivariable logistic regression modeling to control for risk factors for MZT did not correct for this clustering effect, with both high-risk interval (clustering) and extended embryo culture remaining significant.

CONCLUSION

This study supports our hypothesis that MZT occurs in clusters and that this clustering effect could not be explained by demographics and cycle characteristics alone. Although we are unable to explain the clustering phenomenon, this study is important as it highlights high-risk intervals for MZT and opens the door to performing a more detailed investigation, to identify the mechanisms responsible for the spikes of MZT incidence.