Clinical outcomes of transfer of frozen and thawed single blastocysts derived from nonpronuclear and monopronuclear zygotes.

PURPOSE: In assisted reproductive technology, normal zygotes are bipronuclear (2PN) during fertilization confirmation; however, sometimes, nonpronuclear zygotes (0PN) and monopronuclear zygotes (1PN) are found during routine observations. METHODS: To elucidate the clinical usefulness of in vitro-fertilized embryos, we investigated the rates of clinical pregnancy, live birth, miscarriage, and congenital abnormality after transfer of frozen-thawed 1PN- and 0PN-derived single blastocysts at Denentoshi Ladies Clinic, Kanagawa, Japan. RESULTS: The rates of pregnancy and live birth for 1PN-derived blastocysts obtained by conventional in vitro fertilization were 37.5% and 27.1%, respectively, which was not significantly different from those for 2PN-derived blastocysts; however, the rates for 0PN-derived blastocysts were significantly lower. The pregnancy and live birth rates for 0PN-derived embryos obtained by intracytoplasmic sperm injection (ICSI) were 45.7% and 34.8%, respectively, which was not significantly different from those for 2PN-derived blastocysts; however, the rates for 1PN-derived blastocysts were significantly lower (4.0% for both) than those for 2PN- and 0PN-derived blastocysts. No congenital abnormalities were found in infants resulting from transfer of 0PN- or 1PN-derived blastocysts. CONCLUSIONS: Both 1PN- and 0PN-derived blastocysts can be used for embryo transfer; however, care should be taken in making decisions about 1PN-derived blastocysts, especially if they are obtained by ICSI.

Nonpronuclear- and monopronuclear-derived blastocysts do not impair subsequent perinatal and maternal outcomes.

CONTEXT: The routine clinical practice is to prioritize the transfer of blastocysts derived from 2PN embryos if they are available. For women who only have blastocysts resulting from 0PN and 1PN embryos, whether to transfer these embryos or discard them has been an ongoing debate over the years. OBJECTIVE: To investigate the perinatal and obstetric outcomes following the transfer of vitrified-warmed single blastocysts derived from 0PN and 1PN zygotes. DESIGN: Retrospective cohort study. SETTING: University-affiliated IVF center. PATIENT(S): This study included singletons born to women who had undergone 0PN and 1PN vitrified-warmed single blastocyst transfers, compared to those resulting from 2PN vitrified-warmed single blastocyst transfers from 2012 to 2020. INTERVENTIONS: None. MAIN OUTCOME MEASURE(S): Perinatal and obstetric outcomes. RESULT(S): A total of 7,284 women were included in the final analysis. Of these, 386, 316, and 6582 cycles resulted from 0PN-, 1PN-, and 2PN-derived blastocysts transfer, respectively. The rates of clinical pregnancy, miscarriage, and live birth were similar across the study cohorts in both unadjusted and adjusted analyses. When comparing the 0PN and 2PN groups, no differences were found in birth outcomes after adjusting for confounders. Similarly, maternal complications and mode of delivery were comparable between these two study cohorts. Birth parameters were also similar between the 1PN and 2PN blastocyst groups, except for more male births in the 1PN cohort. Furthermore, a comparison between the 1PN and 2PN groups did not reveal any significant differences in maternal outcomes. CONCLUSION: The current study showed that the transfer of 0PN and 1PN blastocysts did not compromise reproductive outcomes or increase maternal and perinatal complications. This information is valuable for clinicians to counsel couples effectively and guide them in making informed decisions.

Obstetric and neonatal outcomes after the transfer of vitrified-warmed blastocysts developing from nonpronuclear and monopronuclear zygotes: a retrospective cohort study.

OBJECTIVE: To evaluate the obstetric and neonatal outcomes after the transfer of vitrified-warmed single blastocysts developing from nonpronuclear (0PN) and monopronuclear (1PN) zygotes. DESIGN: Cohort study. SETTING: Affiliated hospital. PATIENT(S): This study was a retrospective analysis of 435 0PN and 281 1PN vitrified-warmed single blastocyst transfers, and 151 0PN and 75 1PN singletons, compared with 13,167 two-pronuclear (2PN) vitrified-warmed single blastocyst transfers and 4,559 2PN singletons, respectively. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Pregnancy rate (PR), abortion rate (AR), live birth rate (LBR), and singleton birthweight were the primary outcome measures. RESULT(S): PR, AR, and LBR were similar when compared between the 0PN and 2PN groups after vitrified-warmed blastocyst transfer. However, the 0PN group had a higher birthweights, higher z scores, and a greater proportion of very large for gestational age newborns. When comparing the 1PN and 2PN groups, we found that the PR was similar whereas the AR was higher and the LBR was lower. No differences were detected in the other neonatal outcomes. CONCLUSION(S): The results of the present study show that the transfer of 2PN blastocysts should be prioritized because of a higher AR and a lower LBR after 1PN blastocyst transfers and a higher birthweight after 0PN blastocyst transfers when compared with 2PN blastocyst transfers. Our data indicate the need for concern about the safety of 1PN and 0PN embryo transfers.