Differences in clinical outcomes between men with mosaic Klinefelter syndrome and those with non-mosaic Klinefelter syndrome.

Purpose: This study compared the clinical outcomes of men with Klinfelter syndrome based on karyotype. Methods: The authors analyzed the outcomes of microdissection testicular sperm extraction (micro-TESE) performed on 57 patients with Klinfelter syndrome (KS) at our clinic. Results: The average ages of the non-mosaic and mosaic KS groups were 32.2 ± 4.8 and 45.9 ± 13.1 years, respectively. The sperm retrieval rates of the non-mosaic and mosaic KS groups were 46.5% (20/43) and 50.0% (7/14), respectively. The fertilization rates after intracytoplasmic sperm injection did not significantly differ between the non-mosaic and mosaic KS groups. The mosaic KS group had higher cleavage and blastocyst development rates than the non-mosaic KS group (72.2% vs. 96.2% and 30.5% vs. 44.7%, respectively). The group using motile sperm had better outcomes than the group using immotile sperm. The embryo transfer outcomes of the non-mosaic and mosaic KS groups did not significantly differ (clinical pregnancy rate: 28.0% vs. 20.7%, miscarriage rate: 14.3% vs. 33.3%, production rate per transfer: 22.0% vs. 13.8%, and production rate per case: 58.8% vs. 57.1%). Conclusions: Compared with the non-mosaic KS group, the mosaic KS group had significantly better intracytoplasmic sperm injection outcomes because of the higher utilization rate of motile sperm.

Risk factors for placenta accreta spectrum in pregnancies conceived after frozen-thawed embryo transfer in a hormone replacement cycle.

OBJECTIVE: Assisted reproductive technology (ART), especially frozen-thawed embryo transfer (FET) in a hormone replacement cycle (HRC), is a risk factor for placenta accreta spectrum (PAS). This study aimed to clarify the risk factors for PAS related to the maternal background and ART techniques in pregnancies achieved after FET in an HRC. STUDY DESIGN: We performed a case-control study in two tertiary perinatal centres in Japan. Among 14,028 patients who delivered at ≥24 weeks of gestation or were transferred after delivery to two tertiary perinatal centres between 2010 and 2021, 972 conceived with ART and 13,056 conceived without ART. PAS was diagnosed on the basis of the FIGO classification for the clinical diagnosis of PAS or retained products of conception after delivery at ≥24 weeks of gestation. We excluded women with fresh embryo transfer, FET with a spontaneous ovulatory cycle, a donor oocyte cycle, and missing details of the ART treatment. Finally, among women who conceived after FET in an HRC, 62 with PAS and 340 without PAS were included in this study. Multivariate logistic regression models were used for case-control comparisons, with adjustment for maternal age at delivery, parity, endometriosis or adenomyosis, the number of previous uterine surgeries of caesarean section, myomectomy, endometrial polypectomy or endometrial curettage, placenta previa, the stage of transferred embryos, and endometrial thickness at the initiation of progestin administration. RESULTS: PAS was associated with ≥2 previous uterine surgeries (adjusted odds ratio, 3.57; 95 % confidence interval, 1.60-7.97) and the stage of embryo transfer (blastocysts: adjusted odds ratio, 2.89; 95 % confidence interval, 1.15-7.26). In patients with <2 previous uterine surgeries, PAS was associated with an endometrial thickness of <7.0 mm (adjusted odds ratio, 5.18; 95 % confidence interval, 1.10-24.44). CONCLUSION: Multiple uterine surgeries and the transfer of blastocysts are risk factors for PAS in pregnancies conceived after FET in an HRC. In women with <2 previous uterine surgeries, a thin endometrium before FET is also a risk factor for PAS in these pregnancies.

Clinical outcomes of personalized blastocyst embryo transfer after endometrial receptivity analysis: A multicenter, retrospective cohort study.

Purpose: To evaluate clinical outcomes after endometrial receptivity analysis (ERA). Methods: This was a multicenter, retrospective cohort study involving 861 women who underwent ERA testing at certified fertility clinics in Japan, and who received subsequent personalized blastocyst embryo transfers (ET) between 2018 and 2020. Clinical outcomes, including pregnancies, miscarriages, and live births, were evaluated according to receptivity status for ERA. Results: Mean patient age was 37.7 years (SD = 4.0), and the median number of previous ETs was 2 (interquartile range, 2-3). 41.0% (353/861) of patients were non-receptive for ERA testing. Clinical pregnancy, miscarriage, and live birth rates for personalized blastocyst ET were 44.5% (226/508), 26.1% (59/226), and 26.8% (136/508) for receptive patients, and 43.1% (152/353), 28.3% (43/152), and 28.9% (102/353) for non-receptive patients, all statistically nonsignificant. Multiple logistic regression demonstrated similar nonsignificant associations between receptivity and clinical outcomes. Greater patient age, smoking, and longer duration of infertility were significantly and negatively associated with receptivity, whereas a history of delivery was positively associated and statistically significant. Conclusions: Clinical outcomes after ERA testing were similar between receptive and non-receptive patients. Further prospective study including an appropriate comparison group are warranted to evaluate the efficacy of ERA testing.

A novel system based on artificial intelligence for predicting blastocyst viability and visualizing the explanation.

Purpose: The purpose of the study was to invent and evaluate the novel artificial intelligence (AI) system named Fertility image Testing Through Embryo (FiTTE) for predicting blastocyst viability and visualizing the explanations via gradient-based localization. Methods: The authors retrospectively analyzed 19 342 static blastocyst images with related inspection histories from 9961 infertile patients who underwent in vitro fertilization. Among these data, 17 984 cycles of single-blastocyst transfer were used for training, and data from 1358 cycles were used for testing purposes. Results: The prediction accuracy for clinical pregnancy achieved by a control model using conventional Gardner scoring system was 59.8%, and area under the curve (AUC) was 0.62. FiTTE improved the prediction accuracy by using blastocyst images to 62.7% and AUC of 0.68. Additionally, the accuracy achieved by an ensemble model using image plus clinical data was 65.2% and AUC was 0.71, representing an improvement in prediction accuracy. The visualization algorithm showed brighter colors with blastocysts that resulted in clinical pregnancy. Conclusions: The authors invented the novel AI system, FiTTE, which could provide more precise prediction of the probability of clinical pregnancy using blastocyst images secondary to single embryo transfer than the conventional Gardner scoring assessments. FiTTE could also provide explanation of AI prediction using colored blastocyst images.

Developmental trajectory of monopronucleated zygotes after in vitro fertilization when they include both male and female genomes.

OBJECTIVE: To examine the cause of monopronucleated zygote (1PN) formation that includes both maternal and paternal genomes. DESIGN: Retrospective cohort study. SETTING: Private fertility clinic. PATIENT(S): A total of 44 1PN and 726 2-pronuclear zygotes from 702 patients were observed using 2 different time-lapse observation systems. INTERVENTION(S): Previously recorded time lapse data were reviewed to examine the mechanism of 1PN formation. MAIN OUTCOME MEASURE(S): The distance between the position of the second polar body extrusion and the fertilization cone or epicenter/starting position of the cytoplasmic wave was measured, and the consequent data were analyzed. Cytoplasmic waves were confirmed using vector analysis software. RESULT(S): The cut-off value for the difference in the distance between the position of the second polar body extrusion and the fertilization cone or the epicenter/starting position of the cytoplasmic wave was 17 µm (AUC: 0.987, 95% CI: 0.976-0.999) for the Embryo Scope and 18 µm (AUC: 0.972, 95% CI: 0.955-0.988) for the iBIS time-lapse observation systems. CONCLUSION(S): In this study, it was found with a high degree of accuracy that a monopronucleus is formed when the fusion of the sperm takes place within 18 µm from the point of the second polar body extrusion. The theoretical chance of 1PN occurrence after in vitro fertilization is 2.7% when the sperm is considered to be fused anywhere in the plasma membrane of an oocyte.

Clinical outcome of intrauterine infusion of platelet-rich plasma in patients with recurrent implantation failure.

PURPOSE: This study aimed to evaluate the effectiveness of intrauterine infusion of platelet-rich plasma (PRP) before embryo transfer (ET) in recurrent implantation failure (RIF) cases. METHODS: The authors retrospectively analyzed 54 ET cycles involving frozen and thawed high-quality blastocysts after intrauterine PRP infusion between September 2019 and November 2020. All patients had a history of at least two times of implantation failure on ET. A total of 54 patients were categorized into two groups: thin endometrium (39 patients) and unexplained implantation failure (15 patients). In the thin-endometrium group, the endometrial thickness (EMT) was <8.0 mm at cycle days 12-14 in the prior ET cycle. RESULTS: Among the 54 ET cycles after PRP infusion, 31 (57.4%) were positive for human chorionic gonadotropin (hCG) and 27 (50%) achieved clinical pregnancy, which was significantly better than that in prior ET cycles without PRP infusion (27.2% and 9.6%, respectively). The EMT was not increased at ET date on the PRP cycle compared with that in the prior ET cycle in both patient groups. Moreover, EMT was not different between the hCG-positive and hCG-negative groups. CONCLUSION: Although intrauterine PRP infusion had no superior effect on increasing the EMT than conventional therapeutic agents, it resulted in high pregnancy rates in patients experiencing RIF with or without thin endometrium.

Masked high progesterone levels during in vitro fertilization and embryo transfer treatment in a patient with 21-hydroxylase deficiency: A case report.

The most common form of congenital adrenal hyperplasia is 21-hydroxylase deficiency (21OHD). Women with 21OHD have reduced fertility because of excessive production of adrenal androgen and progesterone, which can inhibit folliculogenesis, disturb the normal gonadotropin secretion pattern and development of the endometrium, and affect endometrial receptivity. Here, we report on an infertile woman with 21OHD who initially showed normal progesterone levels and spontaneous ovulation with the treatment by an endocrinologist. However, in vitro fertilization and embryo transfer repeatedly failed because of a gradual elevation in progesterone, which was masked by fertility treatment. The case underlines that close coordination is required between the endocrinologist and reproductive specialist for the total treatment for woman with 21OHD.

Clinical Outcomes of Rescue Intracytoplasmic Sperm Injection at Different Timings Following In Vitro Fertilization.

BACKGROUND: Although rescue intracytoplasmic sperm injection (r-ICSI) is extensively used worldwide, the indication of r-ICSI and its optimal timing remains obscure. This study aimed to assess the outcomes of r-ICSI following in vitro fertilization in different timings when fertilization is confirmed. METHODS: This study included 5,156 cycles (47,785 eggs). Fertilization was confirmed by polar body analysis after 4 and 6 hr of coincubation of the sperm and oocyte. Oocytes that underwent IVF were divided into two groups based on the time when a second polar body was detected in more than 30% of all oocytes (Four-hr group and six-hr group). If the second polar body was not detected or was present in less than 30% of all oocytes after six hr of coincubation, rescue-ICSI (r-ICSI) was performed for oocytes without a second polar body (r-ICSI group). RESULTS: The fertilization rates of two pronuclear (2PN) oocytes in the three groups (Four-hr group, six-hr group, and r-ICSI group) were 70.7%, 51.3%, and 58.0%, respectively. The blastocyst formation rates were 62.8%, 53.4%, and 42.9%, respectively. CONCLUSION: Performing r-ICSI after six hr of coincubation can salvage cases with fertilization failure in IVF. The higher fertilization rate of r-ICSI indicates that all oocytes without signs of fertilization after six hr of coincubation should undergo r-ICSI.

A retrospective analysis of ovarian response to gonadotropins after laparoscopic unilateral or bilateral salpingectomy for hydrosalpinges.

BACKGROUND AND AIMS: We compared the effects of unilateral and bilateral salpingectomy for hydrosalpinx on ovarian function, oocyte retrieval, and embryogenesis. METHODS: We retrospectively examined the hospital records of 109 women with unilateral hydrosalpinx and 57 women with bilateral hydrosalpinges who had undergone in vitro fertilization (IVF) treatment (280 oocyte retrieval cycles) between January 2011 and December 2018. We compared age at oocyte retrieval, level of anti-Müllerian hormone (AMH) measured within 1 year of oocyte retrieval, duration of infertility, number of previous IVF treatments, level of follicle stimulating hormone, total gonadotropin dose, number of oocytes retrieved, fertilization rate, blastocyst formation rate, and peak serum estrogen concentration. This study was approved by the institutional review board. RESULTS: Of the women with unilateral hydrosalpinx, no significant differences were observed in ovarian response, rate of fertilization or rate of blastocyst production between the 21 women (24 cycles) who had undergone unilateral salpingectomy and the 88 women (146 cycles) who had not. Of the women with bilateral hydrosalpinges, the 13 (24 cycles) who had undergone bilateral salpingectomy had slightly lower AMH levels and significantly fewer oocytes retrieved (5.5 ± 3.9 vs 8.3 ± 5.5; P = .0068) than the 44 women (86 cycles) who had not had a salpingectomy. Women who had undergone bilateral salpingectomy also had significantly lower peak serum estrogen concentrations than those who had not undergone salpingectomy (1876.1 ± 765.9 vs 2489.5 ± 1551.4; P = .009). CONCLUSION: In women with hydrosalpinx, bilateral salpingectomy may reduce ovarian function and response to gonadotropins, especially the number of oocytes retrieved. Unilateral salpingectomy does not have these effects.

The inclusion of blastomeres into the inner cell mass in early-stage human embryos depends on the sequence of cell cleavages during the fourth division.

The fate of the ICM in humans is still unknown, due to the ethical difficulties surrounding experimentation in this field. In this study we have explored the existing time-lapse recording data of embryos in the early stages of development, taking advantage of the large refractile bodies (RBs) within blastomeres as cellular markers. Our study found that the cellular composition of the ICM in humans is largely determined at the time of the fourth division and blastomeres which cleave first to fourth, during the fourth division from 8 cells to 16 cells, have the potential to be incorporated in the ICM.

Predictive factors influencing pregnancy rate in frozen embryo transfer.

PURPOSE: To evaluate the outcomes of embryo transfer (ET) and to identify the parameters influencing pregnancy outcomes. METHODS: This study included 938 ET cycles involving single frozen and thawed good-quality blastocyst (Gardner grade ≥3BB) between August 2017 and January 2018. The significance of several parameters including endometrial thickness, position of the transferred air bubble, self-evaluation score by physicians, and uterus direction at ET as predictors of clinical pregnancy was evaluated using univariate and multivariate analyses. RESULTS: Among 938 ET cycles, 462 (49.3%) resulted in a clinical pregnancy. Endometrial thickness was positively associated with clinical pregnancy in a linear trend. Between the variable position of the transferred air bubble and clinical pregnancy rate showed a curvilinear relationship. Clinical pregnancy rate was higher in cases with good self-evaluation score, whereas there was no difference between groups with different uterus directions. Univariate analysis of predictive parameters identified endometrial thickness, self-evaluation score by physicians, and position of air bubbles as significant predictors of clinical pregnancy, of which endometrial thickness and position of air bubbles appeared to be independently related to clinical pregnancy. CONCLUSION: Endometrial thickness and the position of transferred air bubbles influenced clinical pregnancy in ET cycles.

Sperm retrieval from a male with the rare 47, XXYqs variant of Klinefelter syndrome for intracytoplasmic sperm injection: A case report.

A 27-year-old man with nonobstructive azoospermia was diagnosed with Klinefelter syndrome (KS) with a satellite Y chromosome (47, XXYqs) by karyotyping. Genetic analysis revealed azoospermia factor c (AZFc) microdeletion of gr/gr deletion in the Y chromosome. Microdissection testicular sperm extraction (micro-TESE) was performed in bilateral testes. Very few seminiferous tubules were bilaterally observed, and a minute number of spermatozoa obtained from the left testis were cryopreserved. Histologic examination of the left testicular tissue revealed severe tubular atrophy with only Sertoli cells accompanied by Leydig cell hyperplasia. Oocyte harvest was conducted in his wife in two different cycles after ovarian stimulation, and intracytoplasmic sperm injection was performed for 24 oocytes (8 and 16 oocytes respectively) using thawed spermatozoa. Fertilisation was confirmed in total of 19 oocytes (79.2%), with 15 cleaved embryos (62.5%). Two cleavage-stage embryos were cryopreserved at day 2, but no blastocysts developed. Frozen-thawed embryo transfer was performed using two cleavage-stage (day 2) embryos; however, the wife did not conceive. In conclusion, spermatozoa were successfully obtained by micro-TESE from a patient with 47, XXYqs. Despite failure of conception, the fertilisation and cleavage rates were comparable or better than those reported in patients with "typical" KS.

Noninvasive embryo selection: kinetic analysis of female and male pronuclear development to predict embryo quality and potential to produce live birth.

OBJECTIVE: To evaluate a noninvasive method of examining euploid embryos, focusing on kinetic analyses, from second polar body extrusion to pronuclear membrane breakdown (PNMBD). DESIGN: Retrospective embryo cohort study. SETTING: Private IVF clinic. PATIENT(S): 213 frozen-thawed single blastocyst transfers. INTERVENTION(S): Fertilized oocytes were recorded by means of time-lapse photography, followed by kinetic analysis of female and male pronuclei (PNs). MAIN OUTCOME MEASURE(S): The differences in size between the 2PNs in embryos resulting in live births compared with those of embryos from failed pregnancies were analyzed according to sequential size from early PN stages to PNMBD. RESULT(S): It was found that the difference in areas between male and female PNs immediately before PNMBD is a better predictor of embryo quality if this difference is below a known cutoff value. The size of male PNs 8 hours before the onset of PNMBD should be larger than female PNs (B). The difference in size between male and female PNs 8 hours before PNMBD should be larger than the difference in their size immediately before PNMBD. When normal embryos were defined using the equation (A∪C)∩B, the birth rates for in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) were 68.1% and 50.0%, respectively. For the remaining embryos, defined as abnormal according to the above criteria, birth rates were 9.4% for IVF and 4.2% for ICSI. CONCLUSION(S): We have developed a method for noninvasive embryo evaluation by means of the kinetic analysis of female and male PN growths. This method should enable us to select embryos that have a higher potential for healthy births.

Piezo-assisted ICSI improves fertilization and blastocyst development rates compared with conventional ICSI in women aged more than 35 years.

PURPOSE: Piezo-assisted intracytoplasmic sperm injection (Piezo-ICSI) is reported to be an effective method for inseminating fragile oocytes compared with conventional ICSI (c-ICSI). However, infertile patient groups suitable for Piezo-ICSI have not been elucidated. This study was conducted to determine age groups suitable for Piezo-ICSI using sibling egg controls inseminated by a well-trained embryologist to reduce technical inequalities. METHODS: A total of 947 matured oocytes were inseminated either by Piezo-ICSI or by c-ICSI in sibling oocytes as controls. Fertilization (2 pronuclei, PN), survival, and blastocyst development rates on day (D) 5 and D6 after insemination were compared between the Piezo-ICSI and c-ICSI groups. Further analyses were applied to groups of women >35 or ≤35 years of age. RESULTS: There were no significant differences in fertilization, survival, or blastocyst development rates between the two insemination treatment groups. However, for women >35 years of age, the fertilization (P = .008) and blastocyst development (P = .016) rates with Piezo-ICSI on D5 and D6 were significantly higher than in those subjected to c-ICSI. CONCLUSIONS: Piezo-ICSI was useful for inseminating oocytes from women >35 years of age.

Effectiveness of high-dose transvaginal progesterone supplementation for women who are undergoing a frozen-thawed embryo transfer.

PURPOSE: To evaluate the effectiveness of high-dose progesterone supplementation for women who are undergoing a frozen-thawed embryo transfer (FET). METHODS: Among the 2010 FET cycles that were included in the present study, 1188 were 1200 mg/d of vaginal progesterone, while 822 were 900 mg/d. The dose of progesterone that was used was decided by the treatment period and additional progesterone supplementation was used when the serum progesterone levels were <9 ng/mL on luteal day 5. RESULTS: The clinical pregnancy rate was higher in the 1200 mg group than in the 900 mg group. The mean serum progesterone level on luteal day 5 in the 1200 mg and 900 mg groups was 12.6 ng/mL and 13.4 ng/mL, respectively. The rate of additional progesterone supplementation was higher in the 1200 mg group. A logistic regression analysis identified a younger age (≤37 years) and the use of 1200 mg progesterone as independent predictive factors for the clinical pregnancy outcome. The analysis of the infant outcomes revealed no significant difference in the distribution of birth ages and weights. CONCLUSION: High-dose transvaginal progesterone of 1200 mg/d as luteal support contributed to good pregnancy outcomes.

Phase III trial comparing the efficacy and safety of recombinant- or urine-derived human chorionic gonadotropin for ovulation triggering in Japanese women diagnosed with anovulation or oligo-ovulation and undergoing ovulation induction with follitropin-alfa.

Aim: Outside of Japan, recombinant-human chorionic gonadotropin (r-hCG) is widely used for the induction of final follicular maturation and early luteinization in women undergoing ovulation induction; whereas in Japan, urine-derived hCG (u-hCG) is predominantly used. The primary objective of this study was to demonstrate the non-inferiority of r-hCG to u-hCG for ovulation induction, as assessed by the ovulation rate. Methods: This was an open-label, parallel-group, randomized, multicenter, phase III trial in Japanese women with anovulation or oligo-ovulation secondary to hypothalamic-pituitary dysfunction or polycystic ovary syndrome, undergoing ovulation induction with recombinant-human follicle-stimulating hormone. The women were randomized (2:1) to receive either a single 250 µg s.c. dose of r-hCG or a single 5000 IU i.m. dose of u-hCG for ovulation triggering. Results: Eighty-one women were randomized to either r-hCG (n=54) or u-hCG (n=27). Ovulation occurred in 100% of the participants and treatment with r-hCG was observed to be non-inferior to u-hCG for ovulation induction. Overall, the type and severity of adverse events were as expected for women receiving fertility treatment. Conclusion: This study demonstrated that r-hCG was non-inferior to u-hCG for inducing ovulation. Furthermore, r-hCG demonstrated an expected safety profile, with no new safety concerns identified.

Is human chorionic gonadotropin supplementation beneficial for frozen and thawed embryo transfer in estrogen/progesterone replacement cycles?: A randomized clinical trial.

Aim: Human chorionic gonadotropin (hCG) is used frequently for luteal support in fresh in vitro fertilization cycles as it induces progesterone secretion from the ovaries after oocyte retrieval and modulates the endometrium for implantation in fresh cycles. In contrast, hCG is not usually used for the transfer of cryopreserved-thawed embryos in estrogen/progesterone replacement cycles because ovulation is suppressed. However, several studies have shown that luteinizing hormone and hCG receptors are present in the human endometrium and that hCG can directly induce the decidualization of endometrial stromal cells in vitro. Thus, this study evaluated whether hCG supplementation can be beneficial for cryopreserved-thawed embryo transfer in estrogen/progesterone replacement cycles. Methods: One-hundred-and seventy-three cryopreserved-thawed embryo transfer cycles with estrogen/progesterone replacement were divided randomly into two groups. Transdermal oestradiol was used in combination with vaginal progesterone suppositories for HR. The embryo transfer was performed on day 17 and/or day 20 of the HR therapy cycle in both groups. In Group A, 3000 IU of hCG was administered on days 17, 20, and 23. In Group B, hCG was not used. Results: There was no significant difference in the average age of the patients, the average number of previous assisted reproductive technology cycles, or the average number of embryo transfers between the two groups. The rates of pregnancy and implantation per embryo were 37.2% and 25.3%, respectively, in Group A and 35.6% and 21.7%, respectively, in Group B. The pregnancy and implantation rates were similar in both groups. Conclusion: Supplementation with hCG is not beneficial for cryopreserved-thawed embryo transfer in estrogen/progesterone replacement cycles.

Effects of endometrial injury on frozen-thawed blastocyst transfer in hormone replacement cycles.

Aim: To evaluate whether local endometrial injury would improve the pregnancy rates after frozen-thawed blastocyst transfer in cycles with hormone replacement. Methods: Seventy-seven patients who were aged <40 years with a history of at least three unsuccessful embryo transfers and who underwent frozen-thawed blastocyst transfer during hormone replacement cycles between February and June, 2013 were studied. They were allocated into two groups based on the last digit of their clinical record number: an experimental group (n=22), excluding patients who withheld consent or who were unable to undergo treatment, and a control group (n=55). In the experimental group, the endometrium was scratched once with an endometrial sampler during the luteal phase of the cycle preceding the embryo transfer. Results: There was no significant difference in the baseline characteristics between the groups. The clinical pregnancy rate was 6% in the experimental group and 22% in the control group. Among these, the ongoing pregnancy rate was 100% in the experimental group and 50% in the control group. Conclusion: Endometrial injury might increase the pregnancy rates after frozen-thawed blastocyst transfer and decrease the risk of miscarriage in patients with a history of unsuccessful embryo transfers.

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.

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

Aim: Several studies have indicated that the cause of the increased birthweight of frozen-thawed embryos was associated with assisted reproductive technology (ART) procedures, such as cryopreservation. In the present study, the mean birthweight of singletons was compared between the ovulatory and hormone replacement therapy (HRT) cycles in order to investigate the primary factor that leads to higher birthweights from frozen-thawed embryo transfer (FET). Methods: This retrospective study was carried out from January 2011 to December 2014 on 2738 singletons who were born at 37-41 weeks' gestation, following ART in a single facility. The mean birthweight of the singletons who were born after a fresh embryo transfer (ET) was compared to the mean birthweight of the singletons who were born after a FET. In the FET cycles, the mean birthweight of the singletons was compared between the ovulatory and HRT cycles. Results: The mean birthweight of the singletons who were born after a FET was significantly higher than that of the singletons who were born after a fresh ET. In the FET cycles, the birthweight from the HRT cycles was significantly higher than that from the ovulatory cycles. Among the HRT cycles, there was no difference between the birthweight of the singleton who were born from a blastocyst transfer and those who were born from a cleavage-stage ET. Conclusion: The primary factor to affect the birthweight of singletons might be the pre/postET hormonal environment of the endometrium and not the stage of the transferred embryo nor the frozen-thawed procedure itself.