Analysis of the human zona pellucida during culture: correlation with diagnosis and the preovulatory hormonal environment

Comparative studies on ovary and serum hormone levels in silver and blue foxes and their hybrids

The silver and blue fox appear closely related despite their belonging to different genera, and the male and female fox hybrids are completely sterile in mating inter se or back to either of the parental groups. In the present study, we compared ovarian morphology and serum hormone concentrations among silver foxes, blue foxes, HSBs (silver fox male × blue fox female hybrids) and HBSs (blue fox male × silver fox female hybrids) during the pre-breeding and the breeding period. We found that either the fertile blue and silver foxes or the infertile hybrid foxes showed typical characteristics of ovary, with primordial, primary, secondary, antral and Graafian follicles. The diameters and quantities of different follicle classes in fertile foxes were greater than that in hybrids during the two period, while the thickness of zona pellucida (ZP) represented an opposite trend (P < 0.05). The relative weight of bilateral ovaries in fertile foxes was greater than that in hybrids during the pre-breeding period, while mean serum FSH represented an opposite trend during the breeding period (P < 0.05). The mean serum estradiol in fertile foxes was greater than that in HBS foxes during the pre-breeding period, and greater than hybrids during the breeding period (P < 0.05). These findings indicated that in the infertile hybrid foxes, lower estradiol levels produced by lesser and smaller antral follicles, thicker ZP during the two period, higher FSH levels during the breeding period, could be the basis of interpretations in cases of female fox hybrid infertility.

Assessment of the zona pellucida microdissection on its thickness in mammalian embryos

The zona pellucida (ZP) is a dynamically changing object that plays an important role during the preimplantation stage of embryogenesis. The ZP thickness may affect the implantation success and pregnancy rate, it is considered as a prognostic factor in a number of studies. The study was aimed to assess the dynamic changes in the mouse embryonic ZP thickness after laser assisted hatching (LAH) that involved breaching the ZP integrity at the blastocyst stage. Femtosecond laser pulses were used to perform the zona microsurgery. The zona thickness was measured both at the stage of blastocyst microsurgery (~Е3.5, i.e. 3.5 days of embryogenesis) and at the hatching stage (~Е5). Significant differences in the ZP thickness were revealed in the control group of embryos: from 6.21 µm (Е3.5) to 5.4 µm (Е5). The changes in thickness from 6.6 µm (Е3.5) to 6.2 µm (Е5) observed in the group subjected to LAH were non-significant. Tracing the ZP thickness of a particular embryo from the blastocyst stage to the hatching stage made it possible to estimate the thinning coefficients in the experimental and control groups. The findings that indicate lower tensile strength of the zona in case of LAH can provide the basis for further research on the ZP properties in case of using the embryo cryopreservation protocols.

Assisted hatching on assisted conception (in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI))

BACKGROUND

Failure of implantation and conception may result from inability of the blastocyst to escape from its outer coat, which is known as the zona pellucida. Artificial disruption of this coat is known as assisted hatching and has been proposed as a method for improving the success of assisted conception by facilitating embryo implantation.

OBJECTIVES

To determine effects of assisted hatching (AH) of embryos derived from assisted conception on live birth and multiple pregnancy rates.  SEARCH METHODS: We searched the Cochrane Gynaecology and Fertility Group Specialised Register (until May 2020), the Cochrane Central Register of Controlled Trials (CENTRAL; until May 2020), in the Cochrane Library; MEDLINE (1966 to May 2020); and Embase (1980 to May 2020). We also searched trial registers for ongoing and registered trials (http://www.clinicaltrials.gov - a service of the US National Institutes of Health; http://www.who.int/trialsearch/Default.aspx - The World Health Organization International Trials Registry Platform search portal) (May 2020).

SELECTION CRITERIA

Two review authors identified and independently screened trials. We included randomised controlled trials (RCTs) of AH (mechanical, chemical, or laser disruption of the zona pellucida before embryo replacement) versus no AH that reported live birth or clinical pregnancy data.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures recommended by Cochrane. Two review authors independently performed quality assessments and data extraction.

MAIN RESULTS

We included 39 RCTs (7249 women). All reported clinical pregnancy data, including 2486 clinical pregnancies. Only 14 studies reported live birth data, with 834 live birth events. The quality of evidence ranged from very low to low. The main limitations were serious risk of bias associated with poor reporting of study methods, inconsistency, imprecision, and publication bias. Five trials are currently ongoing. We are uncertain whether assisted hatching improved live birth rates compared to no assisted hatching (odds ratio (OR) 1.09, 95% confidence interval (CI) 0.92 to 1.29; 14 RCTs, N = 2849; I² = 20%; low-quality evidence). This analysis suggests that if the live birth rate in women not using assisted hatching is about 28%, the rate in those using assisted hatching will be between 27% and 34%. Analysis of multiple pregnancy rates per woman showed that in women who were randomised to AH compared with women randomised to no AH, there may have been a slight increase in multiple pregnancy rates (OR 1.38, 95% CI 1.13 to 1.68; 18 RCTs, N = 4308; I² = 48%; low-quality evidence). This suggests that if the multiple pregnancy rate in women not using assisted hatching is about 9%, the rate in those using assisted hatching will be between 10% and 14%. When all of the included studies (39) are pooled, the clinical pregnancy rate in women who underwent AH may improve slightly in comparison to no AH (OR 1.20, 95% CI 1.09 to 1.33; 39 RCTs, N = 7249; I² = 55%; low-quality evidence). However, when a random-effects model is used due to high heterogeneity, there may be little to no difference in clinical pregnancy rate (P = 0.04). All 14 RCTs that reported live birth rates also reported clinical pregnancy rates, and analysis of these studies illustrates that AH may make little to no difference in clinical pregnancy rates when compared to no AH (OR 1.07, 95% CI 0.92 to 1.25; 14 RCTs, N = 2848; I² = 45%). We are uncertain about whether AH affects miscarriage rates due to the quality of the evidence (OR 1.13, 95% CI 0.82 to 1.56; 17 RCTs, N = 2810; I² = 0%; very low-quality evidence).

AUTHORS' CONCLUSIONS

This update suggests that we are uncertain of the effects of assisted hatching (AH) on live birth rates. AH may lead to increased risk of multiple pregnancy. The risks of complications associated with multiple pregnancy may be increased without evidence to demonstrate an increase in live birth rate, warranting careful consideration of the routine use of AH for couples undergoing in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI). AH may offer a slightly increased chance of achieving a clinical pregnancy, but data quality was of low grade. We are uncertain about whether AH influences miscarriage rates.

A narrative review of adjuvants in in vitro fertilisation: evidence for good clinical practice

A review of studies published between January 1, 1984 and January 31, 2019 was performed with the aim of analysing the efficacy and adverse effects of commonly used adjuvants to in vitro fertilisation. The authors preferentially selected recent systematic reviews and randomised control trials (where available) from an electronic literature search. The review showed that low molecular weight heparin, corticosteroids and embryo glue may be of use in selected patient groups. Other adjuncts (such as growth hormone, assisted hatching, endometrial disruption and dehydroepiandrosterone) cannot currently be recommended as collated results showed no overall benefit to clinical pregnancy rates or live birth rates. There is a significant lack of robust evidence in this field, and areas in particular need of further research have been highlighted. In conclusion, caution should be exercised in prescribing adjuvants in in vitro fertilisation, either individually or in combination as further research is needed to ascertain their efficacy. Many adjuvants carry the risk of adverse effects which should also be considered. Patients should be clearly informed of the evidence, and where it is lacking, for these treatments. There is a need for further good quality trials to address the questions regarding best practice.

Application of femtosecond laser microsurgery in assisted reproductive technologies for preimplantation embryo tagging

Femtosecond laser pulses were applied for precise alphanumeric code engraving on the zona pellucida (ZP) of mouse zygotes for individual embryo marking and their identification. The optimal range of laser pulse energies required for safe ZP microsurgery has been determined. ZP was marked with codes in three different planes to simplify the process of embryo identification. No decrease in developmental rates and no morphological changes of embryos post laser-assisted engraving have been observed. ZP thickness of embryos post laser-assisted code engraving has been shown to differ significantly from that of control group embryos at the hatching stage. Due to moderate ZP thinning as compared to its initial width at 0.5 dpc (days post coitum), readability of the code degrades slightly and it still remains recognizable even at hatching stage. Our results demonstrate that application of femtosecond laser radiation could be an effective approach for noninvasive direct embryo tagging, enabling embryo identification for the whole period of preimplantation development.

Use of imaging software for assessment of the associations among zona pellucida thickness variation, assisted hatching, and implantation of day 3 embryos

PURPOSE

The aim of this study was to determine if zona pellucida thickness variation (ZPTV) is associated with implantation and if this relationship changes with use of assisted hatching (AH).

METHODS

Day 3 embryos from single or double embryo transfers (DETs) performed between 2014 and 2016 were included. ZPTV was assessed by examining photographs taken before transfer using an automated image processing platform to segment the zona pellucida (ZP) with an active contour technique. One hundred points were obtained of ZP thickness (ZPT) of each embryo to calculate ZPTV ([maximum ZPT-mean ZPT]/mean ZPT). Logistic regression was used to calculate the odds ratio (OR) and 95% confidence intervals (CI) of implantation by tertile of ZPTV. Maternal age and AH were adjusted for a priori. Other cycle and embryo characteristics were adjusted for if they altered the continuous effect estimate by >10%.

RESULTS

There was no statistically significant association between ZPTV and implantation across tertiles although embryos with greater ZPTV showed a trend of decreased implantation (Tertile 2 (T2) versus Tertile 1 (T1), OR = 0.80, CI = 0.50-1.28; Tertile 3 (T3) versus Tertile 1 (T3), OR = 0.75, CI = 0.47-1.20). While similar nonsignificant trends for the association between ZPTV and implantation were observed across tertiles after stratification of embryos hatched or not, embryos with the greatest ZPTV had slightly higher odds for implantation when AH was utilized (T3 vs. T1: with AH, OR = 0.89, CI = 0.49-1.62; without AH, OR = 0.61, 0.29-1.27).

CONCLUSION

ZPTV was not associated with implantation after day 3 transfer. This finding did not vary by use of AH.

Predicting pregnancy in women undergoing in-vitro fertilization with basal serum follicle stimulating hormone levels between 10.0 and 11.9 IU/L

OBJECTIVE

To evaluate the results of the in vitro fertilization (IVF) cycle outcomes in women whose borderline basal follicle stimulating hormone (FSH) levels were between 10.0 and 11.9 IU/L and to analyze the predictors of pregnancy in this population.

MATERIAL AND METHODS

A prospective cohort study was performed at an academic teaching hospital; participants were infertile couples in which the women were undergoing IVF treatment and had borderline basal highest FSH levels between 10.0 and 11.9 IU/L. Statistical modeling was performed to determine risk factors for pregnancy and clinical pregnancy.

RESULTS

A clinical pregnancy rate of 26.5% per cycle and 35% per patient was found in the study population. Among all subjects and non-intracytoplasmic sperm injection (ICSI) subjects, younger age, higher gravidity, higher number of mature follicles on day of Human Chorionic gonadotrophin (hCG) triggering, higher number of oocytes retrieved, and number of embryos produced were significant discriminators between individuals who conceived and those who did not. However, only the number of embryos predicted those who had a clinical pregnancy when compared with those who did not. Higher gravidity, and basal estradiol (E2) levels, and lower maximum basal FSH levels predicted clinical pregnancy in non-ICSI patients. Among ICSI patients, the only predictor of pregnancy was a thicker endometrium. A trend towards higher pregnancy rates was noted in ICSI patients.

CONCLUSION

We showed that pregnancy rates per cycle and per patient in this population were not significantly different than those in patients with a basal FSH level below 10.0 IU/L. Preliminary evidence suggests that ICSI is the fertilization method of choice in these patients.

Oocytes with a dark zona pellucida demonstrate lower fertilization, implantation and clinical pregnancy rates in IVF/ICSI cycles

The morphological assessment of oocytes is important for embryologists to identify and select MII oocytes in IVF/ICSI cycles. Dysmorphism of oocytes decreases viability and the developmental potential of oocytes as well as the clinical pregnancy rate. Several reports have suggested that oocytes with a dark zona pellucida (DZP) correlate with the outcome of IVF treatment. However, the effect of DZP on oocyte quality, fertilization, implantation, and pregnancy outcome were not investigated in detail. In this study, a retrospective analysis was performed in 268 infertile patients with fallopian tube obstruction and/or male factor infertility. In 204 of these patients, all oocytes were surrounded by a normal zona pellucida (NZP, control group), whereas 46 patients were found to have part of their retrieved oocytes enclosed by NZP and the other by DZP (Group A). In addition, all oocytes enclosed by DZP were retrieved from 18 patients (Group B). No differences were detected between the control and group A. Compared to the control group, the rates of fertilization, good quality embryos, implantation and clinical pregnancy were significantly decreased in group B. Furthermore, mitochondria in oocytes with a DZP in both of the two study groups (A and B) were severely damaged with several ultrastructural alterations, which were associated with an increased density of the zona pellucida and vacuolization. Briefly, oocytes with a DZP affected the clinical outcome in IVF/ICSI cycles and appeared to contain more ultrastructural alterations. Thus, DZP could be used as a potential selective marker for embryologists during daily laboratory work.

Evidence-based reproductive medicine: a critical appraisal

Evidence-based medicine has become the golden standard of good medical practice. I analysed meta-analyses and systematic reviews, the cornerstones of evidence-based medicine, pertaining to two important problems in in vitro fertilization: failed implantation and poor ovarian response to ovarian stimulation. Numerous interventions and procedures have been tried to facilitate implantation and to enhance the ovarian response to stimulation. Notwithstanding the fact that many clinical trials have been performed, very few procedures can as yet stand the critical test of evidence-based medicine. A plea is made for co-ordination between clinicians and reviewers and co-operation between infertility centres to combine their efforts to set up sufficiently powered clinical trials to arrive at more solid evidence for a number of interventions in in vitro fertilization programmes.

Assisted hatching on assisted conception (in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI)

BACKGROUND

Failure of implantation and conception may result from an inability of the blastocyst to escape from its outer coat, which is known as the zona pellucida. Artificial disruption of this coat is known as assisted hatching and has been proposed as a method for improving the success of assisted conception by facilitating embryo implantation.

OBJECTIVES

To determine the effect of assisted hatching (AH) of embryos from assisted conception on live birth and multiple pregnancy rates. 

SEARCH METHODS

We searched the Cochrane Menstrual Disorders and Subfertility Group Specialised Register (August 2012), the Cochrane Central Register of Controlled Trials (CENTRAL) (August 2012), MEDLINE (1966 to August 2012) and EMBASE (1980 to August 2012).

SELECTION CRITERIA

Three authors identified and independently screened trials. We included randomised controlled trials (RCTs) of AH (mechanical, chemical or laser disruption of the zona pellucida prior to embryo replacement) versus no AH that reported live birth or clinical pregnancy.

DATA COLLECTION AND ANALYSIS

Three authors independently performed quality assessments and data extraction.

MAIN RESULTS

Thirty-one trials reported clinical pregnancy data, including 1992 clinical pregnancies in 5728 women. There was no significant difference in the odds of live birth in the AH group compared with the control group (9 RCTs; odds ratio (OR) 1.03, 95% confidence interval (CI) 0.85 to 1.26, moderate quality evidence), with no evidence of significant heterogeneity (P = 0.38) or inconsistency (I(2) = 6%). Analysis of the clinical pregnancy rates from the nine studies which reported live birth showed a non-significant result (OR 1.03, 95% CI 0.85 to 1.25 ).Analysis of all of the studies included in this update (31 RCTs) showed that the clinical pregnancy rate in women who underwent AH was slightly improved, but the level only just reached statistical significance (OR 1.13, 95% CI 1.01 to 1.27, moderate quality evidence). However, it is important to note that the heterogeneity for this combined analysis for clinical pregnancy rate was statistically significant (P = 0.001) and the I(2) was 49%. Subgroup analysis of women who had had a previous failed attempt at IVF found improved clinical pregnancy rates in the women undergoing AH compared with the women in the control group (9 RCTs, n = 1365; OR 1.42, 95% CI 1.11 to 1.81) with I(2) = 20%. Miscarriage rates per woman were similar in both groups (14 RCTs; OR 1.03, 95% CI 0.69 to 1.54, P = 0.90, moderate quality evidence). Multiple pregnancy rates per woman were significantly increased in women who were randomised to AH compared with women in the control groups (14 RCTs, 3447 women; OR 1.38, 95% CI 1.11 to 1.70, P = 0.004, low quality evidence).

AUTHORS' CONCLUSIONS

This update has demonstrated that whilst assisted hatching (AH) does appear to offer a significantly increased chance of achieving a clinical pregnancy, the extent to which it may do so only just reaches statistical significance. The 'take home' baby rate was still not proven to be increased by AH. The included trials provided insufficient data to investigate the impact of AH on several important outcomes. Most trials still failed to report on live birth rates.

Is the zona pellucida thickness of human embryos influenced by women's age and hormonal levels?

OBJECTIVE

To evaluate whether zona pellucida thickness (ZPT) of human embryos is correlated with maternal age, patient's hormonal status, embryo quality, and IVF outcomes.

DESIGN

Prospective study.

SETTING

University-affiliated IVF clinic.

PATIENT(S)

Couples undergoing IVF-ET cycles.

INTERVENTION(S)

Zona measurements, clinical data collection.

MAIN OUTCOME MEASURE(S)

Correlation between the ZPT and maternal age, basal FSH and E(2) levels, stimulation protocols, cause of infertility, embryo quality, and implantation/pregnancy rates.

RESULT(S)

The measurements of ZPT were collected from 5,184 day 3 human embryos originated from 744 IVF patients. The overall mean ZPT was 16.18 ± 2.00 μm. No significant correlation was observed between the ZPT and the patient's age, E(2) values on the day of hCG administration, basal concentration of serum FSH, stimulation protocol, infertility diagnosis, and implantation/pregnancy rates. The ZPT was strongly influenced only by the embryo quality: Embryos with good morphology exhibited considerably thinner ZP compared with those of less favorable morphology (mean 15.87 ± 2.48 μm vs. 16.36 ± 2.57 μm, respectively). The ZPT had no significant impact on the implantation and pregnancy rates.

CONCLUSION(S)

The thickness of the human ZP of day 3 embryos is not influenced by women's age and hormonal levels. The strong correlation between ZPT and embryo quality suggests that thickness of ZP depends on inherent embryo properties. The overall ZPT is not a good predictive indicator for IVF clinical outcomes.

Assisted hatching in assisted reproduction: a state of the art

The World Health Organization estimates that one in six couples experience some delay in conception and an increasing number require treatment by the assisted conception (AC) procedures of in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI).The implantation rate of embryos resulting from in vitro fertilization cycles is generally less than 20%. The exposure of oocytes and embryos to the artificial conditions of in vitro culture may have negative effects on the embryo's ability to undergo normal hatching, resulting in low rates of implantation following IVF and embryo transfer. Human embryos resulting from superovulation develop more slowly in vitro compared to embryos in vivo, manifest a relatively high degree of cytogenetic abnormalities and undergo cellular fragmentation. Artificially disrupting the zona pellucida is known as assisted hatching (AH) and there is some evidence that embryos that have undergone zona manipulation for assisted hatching tend to implant one day earlier than unhatched embryos. A variety of techniques have since been employed to assist embryo hatching, including partial mechanical zona dissection, zona drilling and zona thinning, making use of acid tyrodes, proteinases, piezon vibrator manipulators and lasers. This review will consider the impact of IVF conditions on zona pellucida physiology, zona hardening, different techniques of assisted hatching, who may benefit from assisted hatching and potential hazards.

Zona-free embryo culture: is it a viable option to improve pregnancy rates?

Sporadic reports published during the previous decade have documented pregnancies achieved with transfer of zona-free human embryos. Although the overall efficiency seems to be good and some authors have suggested systematic application for special infertility problems, there have been only a few attempts to compare the benefits of zona-free embryo culture and transfer with the traditional approach using zona-intact embryos. So far, the majority of instances in which zona-free culture has been applied have occurred accidentally. This review summarizes the known functions of the zona pellucida, analyses natural and artificial situations where its function is compromised, including zona hardening and difficult hatching that seem to be related to in-vitro embryo culture, and discusses possible methods and timing for artificial zona removal. With the availability of in-vitro systems capable of replacing important functions of the zona pellucida, routine use of zona-free culture for the whole in-vitro period, after or even before fertilization, is a realistic possibility with potential additional benefits. Based on the increasing amount of animal studies, a systematic comparison is suggested that may eventually diminish the handicaps of the in-vitro situation and lead to simplification of manipulations as well as higher success rates after embryo transfer.

The acrosomal protein Dickkopf-like 1 (DKKL1) facilitates sperm penetration of the zona pellucida

OBJECTIVE

To determine the role of Dkkl1 in mouse development, viability, and fertility.

DESIGN

Prospective experimental study.

SETTING

Government research institution.

ANIMAL(S)

Mice of C57BL/6, B6D2F1/J, and 129X1/SvJ strains, as well as transgenic mice of mixed C57BL/6 and 129X1/SvJ strains were used for the studies.

INTERVENTION(S)

Expression of the Dkkl1 gene was characterized during early mouse development, and the effects of Dkkl1 ablation on reproduction and fertility were characterized in vitro and in vivo.

MAIN OUTCOME MEASURE(S)

Dkkl1 RNA expression was determined by Northern blotting hybridization as well as quantitative reverse transcriptase-polymerase chain reaction assays. In vitro fertilization assays were used to assess fertility of sperm from male mice lacking functional Dkkl1.

RESULT(S)

Dkkl1 is a gene unique to mammals that is expressed primarily in developing spermatocytes and its product localized in the acrosome of mature sperm. Here we show that Dkkl1 also is expressed in the trophectoderm/placental lineage. Surprisingly, embryos lacking DKKL1 protein developed into viable, fertile adults. Nevertheless, the ability of sperm that lacked DKKL1 protein to fertilize wild-type eggs was severely compromised in vitro. Because this defect could be overcome either by removal of the zona pellucida or by the presence of wild-type sperm, Dkkl1, either directly or indirectly, facilitates the ability of sperm to penetrate the zona pellucida. Penetration of the zona pellucida by Dkkl1(-) sperm was delayed in vivo as well as in vitro, but the delay in vivo was compensated by other factors during preimplantation development. Accordingly, Dkkl1-/- males offer an in vitro fertilization model for identifying factors that may contribute to infertility.

CONCLUSION(S)

DKKL1 is a mammalian-specific, acrosomal protein that strongly affects in vitro fertilization, although the effect is attenuated in vivo.

Assisted hatching on assisted conception (IVF and ICSI)

BACKGROUND

Failure of implantation and conception may result from an inability of the blastocyst to escape from its outer coat, known as the zona pellucida. Artificial disruption of this coat is known as assisted hatching (AH) and has been proposed as a method for improving the success of assisted conception.

OBJECTIVES

To determine whether assisted hatching (AH) of embryos facilitates live births and clinical pregnancy.

SEARCH STRATEGY

We previously searched the Cochrane Menstrual Disorders and Subfertility Group Specialsed Register (February 2007), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2007), MEDLINE (1966 to February 2007) and EMBASE (1980 to February 2007).

SELECTION CRITERIA

Two authors identified and independently screened trials. We included randomised controlled trials (RCTs) of AH (mechanical, chemical or laser disruption of the zona pellucida prior to embryo replacement) versus no AH, which reported live birth or clinical pregnancy rates.

DATA COLLECTION AND ANALYSIS

Two authors independently performed qualitative assessments and data extraction.

MAIN RESULTS

Twenty-eight trials reported clinical pregnancy data, including 1228 clinical pregnancies in 3646 women. There was no significant difference in the odds of live births in the AH compared with control groups (seven RCTs; OR 1.13, 95% CI 0.83 to 1.55; 255 births from 719 women, with no heterogeneity (P = 0.37) or inconsistency I(2) = 8%)). We also analysed the clinical pregnancy rate from the seven studies that reported live births, which was non-significant (OR 1.13, 95% CI 0.83 to 1.54). Inclusion of studies which were more robust in methodology showed an increase in clinical pregnancy rate which was just statistically significant (16 RCTs; OR 1.20, 95% CI 1.00 to 1.45, P = 0.05). Analysis of all the studies included in this update (28 RCTs) showed a marked increase in clinical pregnancy rate (OR 1.29, 95% CI 1.12 to 1.49).Miscarriage rates per women were similar in both groups (14 RCTs; OR 1.13, 95% CI 0.74 to 1.73). Multiple pregnancy rates per woman were significantly increased in women who were randomised to AH compared with women in control groups (12 RCTs; OR 1.67, 95% CI 1.24 to 2.26).

AUTHORS' CONCLUSIONS

The improvement in clinical pregnancy rate (CPR) with AH means that a clinic with a success rate of 25% could anticipate improving the CPR to between 29% and 49%, all things being equal. The included trials provided insufficient data to investigate the impact of assisted hatching on several important outcomes.

[Laser assisted hatching: Rouen University Hospital outcomes]

OBJECTIVE

Despite technical progress in In Vitro Fertilisation (IVF) procedure, embryo implantation rate remains low. Assisted hatching has been proposed to facilitate natural embryo hatching and implantation.

PATIENTS AND METHODS

Our study has evaluated whether laser assisted hatching improves implantation, pregnancy and live birth rates in different cases. We studied retrospectively 143 IVF cycles concerning more than 38 years old women, 166 IVF cycles after two previous implantation failures and 180 frozen-thawed embryo transfers.

RESULTS

Population characteristics were comparable in hatched and control groups. Implantation, pregnancy and live birth rates in women more than 38 years old were comparable with or without assisted hatching. Concerning repeated implantation failures, even if implantation, pregnancy and live birth rates were higher in assisted hatching group (FIV or ICSI), the differences were not significant. After frozen-thawed embryo transfers, implantation rate was significantly better with assisted hatching (19.14% vs 8.84% [p=0.02]).

DISCUSSION AND CONCLUSION

Assisted hatching improves embryo implantation rate after frozen-thawed embryo transfer.

Impact of assisted hatching on fresh and frozen-thawed embryo transfer cycles: a prospective, randomized study

The aim of this study was to determine if assisted hatching (AH) could improve the rates of pregnancy and implantation for both fresh and frozen-thawed embryo transfer cycles. A total of 760 fresh embryo transfer cycles and 200 frozen-thawed embryo transfer cycles were randomly assigned to either the treatment group (AH) or the control group (no AH). Zona thinning by laser was performed just before embryo transfer. In fresh embryo transfer cycles, the AH group and control group results were comparable. There were no significant differences in the rates of positive human chorionic gonadotrophin (HCG; 47.5 versus 48.8%), clinical pregnancy (42.4 versus 42.6%), or implantation (26.3 versus 25.2%) between the two groups. However, in frozen-thawed embryo transfer cycles, the rates of positive HCG (32.0 versus 17.0%), clinical pregnancy (25.0 versus 14.0%) and implantation (16.7 versus 7.3%) were significantly greater in the AH group than in the control group (P &lt: 0.05). The results of this investigation show that in the fresh embryo transfer cycles, laser-assisted hatching by zona thinning has no impact on the rates of positive HCG, clinical pregnancy and implantation, whereas in frozen-thawed cycles, assisted hatching by zona thinning significantly increases all three of these rates.

Laser assisted hatching in good prognosis patients undergoing in vitro fertilization-embryo transfer: a randomized controlled trial

OBJECTIVE

To evaluate whether assisted hatching improves clinical outcomes of embryo transfers to good prognosis patients, defined as patients < or =39 years with normal follicle-stimulating hormone (FSH) and E(2) levels, no more than one previous unsuccessful cycle of in vitro fertilization (IVF)-embryo transfer, and good embryo quality.

DESIGN

Prospective randomized controlled trial.

SETTING

Private assisted reproductive technology (ART) center.

PATIENT(S)

One hundred ninety-nine good prognosis patients undergoing IVF-embryo transfer.

INTERVENTION(S)

In vitro fertilization followed by embryo transfer on day 3 after oocyte retrieval with or without assisted hatching using a 1,480-nm wavelength infrared laser.

MAIN OUTCOME MEASURE(S)

Clinical intrauterine pregnancy, spontaneous pregnancy loss, and live birth.

RESULT(S)

Rates of clinical intrauterine pregnancy with fetal cardiac activity (53% vs. 54% per cycle), spontaneous pregnancy loss (13% vs. 16% per pregnancy), and live birth (47% vs. 46% per cycle) were very similar between treatment cycles with laser-assisted hatching and control cycles in which embryos were transferred without assisted hatching. There were no significant differences between treatment and control groups in any measured clinical outcome parameters.

CONCLUSION(S)

Assisted hatching does not improve clinical outcomes among good prognosis patients.

Prediction of embryo developmental potential and pregnancy based on early stage morphological characteristics

OBJECTIVE

To analyze the association between morphological details at different stages of culture with blastocyst development, with an aim to improve selection for transfer.

DESIGN

Retrospective audit of data.

SETTING

Tertiary referral center and university hospital.

PATIENT(S)

Two hundred sixty-eight couples underwent 357 treatment cycles.

INTERVENTION(S)

Oocyte pickups for IVF or intracytoplasmic sperm injection (ICSI) after ovarian stimulation. Embryos were individually cultured and examined on days 0-2 for morphological details and developmental characteristics, and selected for transfer, freezing, or further culture.

MAIN OUTCOME MEASURES

The association of blastocyst development and pregnancy with morphological characteristics.

RESULT(S)

Five morphological characteristics (appearance of the cytoplasm, pronuclei and nucleoli, cytoplasmic deficit, and developmental rate) showed the strongest association with blastocyst development. By combining information from all days of culture into a cumulative score, prediction was greatly improved, compared to only using day 2 morphology. Cytoplasmic dysmorphisms of the oocyte, including accumulation of smooth endoplasmic reticulum, were associated with poor developmental performance. Differential weighting of these characteristics was included in a new embryo scoring system, which showed a strong correlation with implantation.

CONCLUSION(S)

Weighting individual morphological characteristics of zygotes and embryos and combining them into a cumulative embryo score can improve selection of embryos for transfer.

Use of laser-assisted intracytoplasmic sperm injection (ICSI) in patients with a history of poor ICSI outcome and limited metaphase II oocytes

In this study, laser-assisted intracytoplasmic sperm injection (ICSI) improved the fertilization rate and the embryo quality in patients with a history of poor ICSI outcome and with limited metaphase II oocytes. This technique is less traumatic to the oocytes during the procedure, and the use of the technique may be expanded.

Assisted hatching on assisted conception (IVF & ICSI)

BACKGROUND

Failure of implantation and conception may result from an inability of the blastocyst to escape from its outer coat, know as the zona pellucida. In vitro culture conditions and/or advancing maternal age may alter the architecture of the zona pellucida and result in hatching difficulties. Artificial disruption of this coat is known as assisted hatching (AH) has been proposed as a method of improving the success of assisted conception.

OBJECTIVES

To determine whether assisted hatching (AH) of embryos facilitates live births and clinical pregnancy and whether it impacts on negative outcomes (such as multiple pregnancy and miscarriage).

SEARCH STRATEGY

We searched the Cochrane Menstrual Disorders and Subfertility Group trials register (1 June 2005), the Cochrane Controlled Trials Register (Cochrane Library Issue 2, 2005), MEDLINE (1996 to June 2003), EMBASE (1980 to June 2005) and reference lists of articles. Authors were contacted for missing and/or unpublished data.

SELECTION CRITERIA

Trials were identified and independently screened by two reviewers. Randomised controlled trials of AH (mechanical, chemical or laser disruption of the zona pellucida prior to embryo replacement) versus no AH that reported live birth, clinical pregnancy or implantation rates were included.

DATA COLLECTION AND ANALYSIS

Qualitative assessments and data extraction were performed independently by two reviewers. Outcomes were extracted as rates and combined using random effects meta-analysis, sensitivity analysis, sub grouping and meta-regression where appropriate.

MAIN RESULTS

Twenty-three randomised controlled trials consisting of 2668 women reported on 849 pregnancy outcomes. There was no significant difference in the odds of live births in the AH compared with control groups (6 RCTs; OR 1.19 95% CI 0.81 to 1.73; 163 births from 516 women). Women undergoing assisted hatching were significantly more likely to achieve clinical pregnancy (23 RCTs, OR 1.33, 95% CI 1.12 to 1.57). Miscarriage rates per woman were similar in both groups (12 RCTs OR 1.23 (95% CI 0.73 to 2.05). Multiple pregnancy rates per woman was increased in women who were randomised to AH compared with control women (9 RCTs OR 1.83 (95% CI 1.19 to 2.83). The improvement in clinical pregnancy rate means for a clinic with a success rate of 25% could anticipate improving the CPR to between 28 and 39%, all things being equal. The trials provided insufficient data to investigate the impact of assisted hatching on several important outcomes, including monozygotic twinning, embryo damage, congenital and chromosomal abnormalities, and in vitro blastocyst development.

AUTHORS' CONCLUSIONS

Despite significantly improved odds of clinical pregnancy, there is insufficient evidence to determine any effect of AH on live birth rates. The increased multiple pregnancy rate is of concern although it likely that with a policy of single embryo transfer this may be lowered. Currently, there is insufficient evidence to recommend assisted hatching.

Effects of assisted hatching method and age on implantation rates of IVF and ICSI

The objective of this study was to investigate whether a change in assisted hatching (AH) technique from total to partial penetration of the zona pellucida improved the outcome of IVF and intracytoplasmic sperm injection cycles where AH was indicated. This was an observational study conducted from the beginning of January 2000 to the end of April 2005. Total AH was performed in 312 cycles, while partial AH was performed in 592 cycles. In women of all ages, implantation, clinical pregnancy and live birth rates were higher in the partial AH group than in the total AH group (12.6 versus 7.2%, P = 0.0001; 22.3 versus 15.7%, P = 0.02; 18.2 versus 12.5%, P = 0.03 respectively). The benefit of partial AH was most marked in women under 38 years old (i.e. the recurrent implantation failure group). The authors conclude that partial AH is associated with higher implantation and pregnancy rates than total AH, especially in women under 38 years old who suffer from recurrent implantation failure.

Impact of assisted hatching on ART outcome in women with endometriosis

BACKGROUND

Assisted hatching can improve the implantation rate in cycles with poor outcome. The impact of assisted hatching in embryos from women with endometriosis is not known. Therefore, the hypothesis that the implantation potential of embryos obtained from women with endometriosis can be improved with assisted hatching was tested.

METHODS

In a prospective randomized study, transfer embryos obtained from 60 women with endometriosis were hatched using a laser system and compared to embryos obtained from patients with the same diagnosis which were left intact (n = 30).

RESULTS

The characteristics of cycles were similar between groups. The pregnancy (40% zona intact, 28.3% assisted hatching), and implantation rates (19.4% zona intact, 17.8% assisted hatching) did not differ in endometriosis cycles regardless of assisted hatching.

CONCLUSION

Assisted hatching does not improve outcome in women with endometriosis undergoing assisted reproduction.

An improved mechanical technique for assisted hatching

BACKGROUND

Varied clinical outcomes of assisted hatching (AH) have been reported. We attempt to investigate whether the size of the zona opening created by AH is adequate for blastocyst hatching, and, if not, set up a new method to improve it.

METHODS

A new AH technique, long zona dissection (LZD), was established, and experiments were performed to compare the effects of different sizes of zona opening on complete hatching of blastocysts in mouse and human embryos in vitro.

RESULTS

The LZD technique can create a long zona slit on early embryos, even blastocysts, with the slit size beyond two-thirds of zona diameter. Compared with three-dimensional partial zona dissection, LZD can significantly enhance the hatching speed and the rate of complete hatching of mouse blastocysts (93.9%). All (100%) human blastocysts completely hatched following LZD; however, when the slit size after AH was about two-fifths of zona diameter, more of the larger inner cell masses (ICM) became trapped by the zona opening during hatching than the smaller ICM (53.3 versus 12.5%, P = 0.01).

CONCLUSIONS

Zona opening of moderate size following AH is inadequate for the completion of blastocyst hatching in vitro; in some cases, however, it can be significantly improved by LZD.

Clinical application of laser-assisted ICSI: a pilot study

Human oocyte survival after intracytoplasmic sperm injection (ICSI) can be compromised by abnormal oolemma breakage patterns during the penetration of the microinjection needle. We previously reported a case of repeated ICSI failures associated with abnormal oolemma breakage in which a substantial improvement and successful pregnancy were achieved by performing ICSI through a laser-drilled hole in the zona pellucida (laser-assisted ICSI). This study was undertaken to compare the efficacy of laser-assisted ICSI with that of conventional ICSI in patients whose oocytes present this particular feature. Oocytes treated by laser-assisted ICSI (n=140) survived better (97.9% versus 85.7%; P<0.05) and tended to form more two-pronucleated zygotes (78.6% versus 69.2%; P=0.07) and less zygotes with three or more pronuclei (2.8% versus 7.8%; P=0.06) as compared with sibling oocytes treated by conventional ICSI (n=140). These data show that laser-assisted ICSI is suitable for oocytes with propensity for sudden oolemma breakage during conventional ICSI. The reduction of oocyte damage with laser-assisted ICSI as compared to conventional ICSI may be useful in other clinical indications where only few oocytes are available or when the oocyte survival after ICSI can be supposed to be compromised.

[Assisted hatching: procedure and effectiveness]

Assisted hatching (AH) has been proposed to improve the implantation rate in patients with poor prognosis for pregnancy. This systematic review of randomized controlled trials addresses primary outcomes of clinical pregnancy and embryo implantation. Several different methods for AH have been introduced over the years but comparative studies are lacking. AH using laser technology is probably the best technique. Assisted hatching increases the pregnancy and implantation rates significantly in patients with a poor prognosis undergoing IVF or ICSI, particularly in older women. More randomized trials are required to confirm any positive effects on the take-home-baby rate and to compare the different techniques.

A prospective randomized controlled study of the effect of short coincubation of gametes during insemination on zona pellucida thickness

A prospective, randomized study was conducted to evaluate the thickness, of zona pellucida (ZP) after brief or standard exposure of human oocytes to spermatozoa, and to determine the correlation between ZP thickness, fertilization rate and embryo quality. The mean ZP thickness 48 h after insemination was found to be significantly less in fertilized oocytes than in non-fertilized oocytes in all treated groups (13.72 +/- 3.0 microns and 15.08 +/- 2.5 microns, respectively; p < 0.007). Zona pellucida thickness correlated positively with embryo quality. Brief exposure of gametes was found to influence ZP thickness. The ZP was significantly thinner after brief and intracytoplasmic sperm injection (ICSI) exposure of oocytes to spermatozoa than after standard in vitro fertilization (IVF). The mean ZP thickness 24 and 48 h after fertilization was significantly greater in standard IVF (16.43 +/- 2.8 microns and 15.22 +/- 2.7 microns, respectively) than in either the brief exposure or ICSI groups (12.78 +/- 2.4 microns and 13.01 +/- 3.5 microns vs. 13.46 +/- 2.2 microns and 13.16 +/- 2.4 microns; p < 0.0001).

A novel approach for patients at risk for ovarian hyperstimulation syndrome: elective transfer of a single zona-free blastocyst on day 5

In this preliminary prospective randomized study of 420 patients undergoing ovarian stimulation for IVF/intracytoplasmic sperm injection (ICSI), 17 patients (4%) developed moderate to severe ovarian hyperstimulation syndrome (OHSS). Re-evaluation for OHSS on day 4 and 6 after oocyte retrieval identified one patient with continuous risk for severe OHSS, resulting in cancellation of the transfer (1/17, 5.8%). Prospectively, two of three patients had the zona pellucida of the blastocyst removed by pronase exposure prior to transfer. Significantly more patients became pregnant when a zona-free blastocyst was transferred in comparison to transfer of a single zona-intact embryo (9/11 or 82% versus 1/5 or 20%; P < 0.01). Higher ongoing singleton pregnancy rates were obtained when the zona pellucida was removed prior to the transfer (6/11 and 1/5 respectively). This preliminary prospective randomized study indicates that by prolonging the evaluation time for patients at risk of developing OHSS for up to 6 days after the oocyte retrieval, those patients at risk for developing severe OHSS can be identified. Transferring a single zona-free day 5 embryo (blastocyst) and freezing of the supernumerary embryos offers the patient with moderate OHSS an optimal chance for a singleton pregnancy, while avoiding the serious maternal complications of ovarian hyperstimulation syndrome.

Laser-assisted intracytoplasmic sperm injection

OBJECTIVE

To improve oocyte survival and fertilization rates after intracytoplasmic sperm injection (ICSI) in patients with inherent oocyte fragility.

DESIGN

Pilot feasibility study and case report.

SETTING

Private hospital.

PATIENT(S)

Infertile couple with repeated failures of ICSI caused by oocyte degeneration.

INTERVENTION(S)

Laser-assisted drilling of the zona pellucida followed by ICSI.

MAIN OUTCOME MEASURE(S)

Oocyte survival, fertilization, and pregnancy.

RESULTS

In a couple with four previous ICSI failures because of poor oocyte survival (33.3%, 0%, 20%, and 18%), a fifth attempt using laser-assisted ICSI resulted in the survival of 8 oocytes out of 13 injected. Normal fertilization occurred in 5 oocytes, and a clinical pregnancy was established.

CONCLUSION(S)

Performing ICSI through a laser-drilled hole in the zona pellucida reduces the risk of oocyte damage related to deformation during the initial phase of the microinjection procedure. This modification of ICSI appears to be suitable for patients whose oocyte show inherent fragility and high degeneration rates after the standard ICSI procedure.

The impact of the zona pellucida thickness variation of human embryos on pregnancy outcome in relation to suboptimal embryo development. A prospective randomized controlled study

BACKGROUND

The study represents a prospective randomized controlled study evaluating zona pellucida thickness variation (ZPTV) measurements versus conventional selection of embryos using classic embryo score criteria, prior to embryo transfer in human IVF/intracytoplasmatic sperm injection (ICSI).

METHODS

Eighty-six patients having > or =3 embryos, with a classic embryo score of < or =2.2, were allocated to either ZPTV measurement or classic embryo morphology score before embryo transfer. The technician selecting embryos using classic embryo scoring was not aware of the ZPTV measurement results. Of the embryos allocated to ZPTV measurements, only the embryos with the highest ZPTV were transferred.

RESULTS

We found no differences in the pregnancy rate per embryo transfer between the two groups (34.4 versus 35.7%). Neither did the implantation rates differ. However, significantly better results were obtained when ZPTV was used as the selection criteria in cases where all embryos had an asynchrony in development or a high embryo score (i.e. were of poorer quality) by classical evaluation (odds ratio = 2.51, confidence interval = 0.33-198).

CONCLUSIONS

Using a normally-developed embryo with an optimal embryo score, no beneficial effect of using ZPTV measurement was seen. However, when only less optimal embryos were available to select for transfer, ZPTV provided a x 2.5 increase in the chance of achieving a clinical pregnancy.

A comparison between quarter, partial and total laser assisted hatching in selected infertility patients

BACKGROUND

The object of this study was to evaluate the efficacy of laser assisted hatching (LAH) of embryos on implantation and pregnancy rates of a selected group of infertility patients.

METHODS

A total of 322 cycles using LAH was undertaken in our Centre between June 1998 and September 1999. Patients were offered LAH if they fell in either one or more of the following categories: (i) Patients over 37 years of age undergoing either IVF or intracytoplasmic sperm injection (ICSI) treatment cycles; (ii) patients with more than 2 previous treatment cycle failures; (iii) patients undergoing frozen embryo replacement cycles and (iv) women who were considered to be poor responders. The initial results of totally breaching the zona pellucida (total LAH; group 1) did not meet with our expectations. We subsequently modified the technique to thinning one area of the zona pellucida (partial LAH; group 2) and this thinned area was then extended to a quarter segment (quarter LAH; group 3).

RESULTS

In group 1, the pregnancy rate was 14.6% with a clinical pregnancy rate of 5.2%. In group 2 the pregnancy rate was 20.9% with a clinical pregnancy rate of 18% and for patients in group 3 the pregnancy rate was 29.0% with a clinical pregnancy rate of 22.1%.

CONCLUSIONS

Overall there was firm statistical evidence that the pregnancy and clinical pregnancy rates arising from quarter LAH were higher in comparison with partial and total LAH.

Laser zona pellucida thinning--an alternative approach to assisted hatching

BACKGROUND

The purpose of this study was to assess the efficacy and hatching characteristics of in-vitro cultured human embryos subjected to laser zona pellucida thinning.

METHOD

Zona thinning was performed on 110 embryos using a non-contact 1.48 microm diode laser and the hatch rate in vitro was compared with 42 control embryos. Variation of zona thickness and degree of zona expansion was assessed. Scanning electron microscopy was performed on embryos entrapped during hatching to identify the site of hatching.

RESULTS

The rate of hatching was significantly higher in laser thinned blastocysts compared with control embryos (68 versus 33% respectively, P < 0.01). Laser thinning increased the variation of zona thickness in embryos from 11.6-27.3%. Natural zona thinning occurred in 92% of laser thinned hatching blastocysts and 100% of control embryos.

CONCLUSION

These results suggest that laser zona thinning is effective and may provide significant advantages over conventional assisted hatching techniques, which create holes.

Pregnancy following fertilization of zona-free, coronal cell intact human ova: Case Report

A pregnancy by intracytoplasmic sperm injection (ICSI) of a couple whose oocytes were recovered without a zona pellucida is reported. Previous IVF/ICSI cycles indicated all oocytes had either very thin or no zona pellucida at the time of cumulus removal prior to ICSI. As a result, many ova were very fragile and lysed upon handling. In the latest attempt, six ova were recovered. After coronal cell dissection of two ova where both lacked a zona pellucida and one lysed, it was elected to attempt to inject the remaining four ova without removal of their coronal cells. The zona pellucida was not visible through the cell layer and the position of the polar body in three ova was speculative. Two embryos possessed normal pronuclei on day 1, and displayed six blastomeres prior to transfer on day 3. During preparation for transfer, sufficient coronal cells fell away to confirm both embryos lacked a zona pellucida. Pregnancy was confirmed by ultrasound observation of a fetal heart 4 weeks later. This report documents that where the zona pellucida is absent, the coronal cells provide sufficient support to maintain blastomere interaction and embryo viability and the zona pellucida is not essential for early embryo development and pregnancy.

Influence of zona pellucida thickness of human embryos on clinical pregnancy outcome following in vitro fertilization treatment

PURPOSE

To evaluate the correlation between the degree of zona pellucida thickness variation (ZPTV) of transferred embryos with identical morphologies and subsequent clinical pregnancy rates during 141 intracytoplasmic sperm injection (ICSI) treatment cycles.

METHODS

A total of 141 women participating in the study group comprising mostly male factor infertilities and some repeat in vitro fertilization (IVF) failures were transferred, 2 days after ovum pickup, with two to three embryos with identical grades created by fertilization with ICSI. All selected embryos were subjected to zona pellucida thickness measurements immediately prior to transfer using a computerized embryo measurement program from videocinematography recordings.

RESULTS

A total of 326 identical-grade transferred pre-embryos resulted in 70 clinical pregnancies with live-born implantation rate of 27.6%. A highly significant correlation was observed between ZPTV of transferred embryos and the IVF outcome with 77.1% and 83.64% of the clinical pregnancies resulting from transferred embryos with ZPTV values greater than 20 and 25, respectively. The mean ZPTV values for 70 conceptual cycles and 62 nonconceptual cycles were 28 +/- 6.43 and 17.85 +/- 8.11, respectively. No significant correlation between ZP thickness and number of blastomeres in the transferred embryos was evident, though embryos with better scores had significantly thinner zonae and higher ZPTV values. Though average zona thickness of embryos declined with age, the mean ZPTV value for women less than 30 years old was significantly higher (25.84 +/- 8.57) as compared with those from women older than 35 years (20.72 +/- 8.45).

CONCLUSIONS

The degree of ZPTV of the transferred embryos exhibits a strong correlation with clinical pregnancy outcome following IVF treatment. This potentially reliable indicator of IVF success rate could be used as a criteria for embryo selection during clinical transfers.