Purpose To provide clinicians with data showing the benefits of transferring a single blastocyst in frozen embryo transfer (FET) cycles so that they may counsel their patients accordingly. Methods This is a closed cohort study of 678 FET cycles occurring between January 2011 and December 2017 in a private IVF laboratory and associated physicians' practice. Patients included in the analysis were less than 38 years of age at oocyte collection, had at least two vitrified blastocysts, and were undergoing their first autologous FET cycle. The patients were categorized into four groups after they had chosen either elective single-embryo transfer (eSET) or double-embryo transfer (eDET). Outcomes for eSET and eDET were compared within groups of patients having freeze-all IVF cycles (PGT-A patient vs. non-PGT-A patient) and fresh IVF transfer groups (negative outcome vs. pregnant/delivered in fresh cycle). Main outcome measures of the study were live birth, multiple pregnancy, and implantation rates. Results There were no statistically significant differences observed in live birth rates for eSET (54-62%) vs. eDET (54-66%) (P = 0.696-1.000) in the four patient groups evaluated. Multiple pregnancy rates were significantly decreased in all eSET groups (0-3%), compared with eDET groups (24-65%) (P = 0.0001-0.037). Conclusions This data shows that transfer of a single vitrified-warmed blastocyst maintains live birth rates, while decreasing multiple pregnancies, and may become more acceptable to physicians and patients.

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MATERIALS AND METHODS: Six 5x5 mm ovarian cortical pieces were harvested from each organ donor cadaver (n¼18 pieces from 3 donors; mean age 31AE8 years) and assigned to either open vitrification (OV) or closed vitrification (CV) in a paired design. Cryopreserved tissues were thawed 8-10 weeks later and evaluated on thaw (0h) and after 24-96h culture. Formalin fixed, paraffinembedded blocks were serially sectioned and primordial (pdf) and primary (pyf) follicle densities, % of pdf and pyf with DNA double-strand breaks (by gH2AX) and apoptotic cell death pathway activation (AC3) were determined.RESULTS: The data are summarized in Table 1. Compared to OV, pdf and pyf densities were similar in the CV group after thawing. Likewise, the percentages of apoptotic and DNA-damaged pdf did not differ between the OVand CV groups on the thaw day. However, the percentage of apoptotic pdf was significantly reduced in the CV group compared to the OV after 96h in culture (p¼0.03).CONCLUSIONS: Our results show that the newly developed CV system provides similar or better efficacy compared to open vitrification with human ovarian tissue. The mechanism of higher primordial follicle survival rate with CVafter 96h culture needs to be further explored. Having showed that the OV has similar efficacy to slow freezing with ovarian tissues (see abstract 2017-A-2005-ASRM), we propose that the CV method should become the standard method of ovarian tissue cryopreservation.

OBJECTIVE: To investigate the effects of single embryo transfer (ET) and double ET on pregnancy outcomes in women with a unicornuate uterus.DESIGN: Retrospective analysis. MATERIALS AND METHODS: The pregnancy outcomes of 300 infertility patients with a unicornuate uterus and got clinical pregnancy via in vitro fertilization (IVF)-ET from January 2012 to May 2015 were analyzed. The rates of embryo implantation, live birth, transfer cycle pregnancy, clinical pregnancy and multiple pregnancy were compared between single and double ET using chi-squared test; comparisons of pregnancy outcomes were made between singleton pregnancy via single ET (A group) and via double ET (B group), and between singleton pregnancy of A group and twin pregnancy via double ET (C group) using two-sample t-test, chi-squared test or fisher exact test.RESULTS: There were a total of 377 transfer cycles in the 300 cases, including 53 single ET cycles which obtained 23 cases of singleton pregnancy and 324 double ET cycles which obtained 126 cases of singleton pregnancy, 74 cases of twin pregnancy and 3 cases of triple pregnancy. 35 cases of spontaneous/selective reduction were excluded from analysis. Comparison of the IVF treatment outcomes based on single or double ET, the rates of transfer cycle pregnancy (43.4%(23/53) vs. 62.7%(203/324), p¼0.008), clinical pregnancy (46.8%(22/47) vs. 76.7%(194/253), p<0.001) and multiple pregnancy in single ET were all significantly lower. While the rates of embryo transplantation (43.4%(23 /53) vs. 43.1%(279/648), p¼0.962) and live birth (37.7%(20/53) vs. 48.4%(157/324), p¼0.147) had no significant differences. There were no significant difference in pregnancy outcomes between A and B group (p¼0.741). When comparing the pregnancy outcomes of A and C group, the differences were significantly different (P¼0.002): the rates of early pregnancy loss (8.7%(2/23) vs. 14.3%(6/42)), late miscarriage (4.3%(1/23) vs. 16.7%(7/42), and preterm delivery (13.0%(3/23) vs. 42.9%(18/42) in A group were all lower; in addition, the gestational weeks at delivery (38.1AE1.9 vs. 35.2AE2.9; p<0.001) and birth weight (3.1AE0.5vs. 2.2AE0.6, kg; p<0.001) in A group were both significantly higher. Although the rates of term low birth weight infant (0 (0/17) vs. 18.2%(4/22); p¼0.118) and perinatal mortality (0 (0/20) vs. 10.7%(6/56); p¼0.331) were both lower in A than C group but didn't reach significant level (Table ).CONCLUSIONS: Single ET could obtain similar rates of embryo implantation and live birth as double ET. Singleton pregnancy via single ET can not only gain better pregnancy outcomes than twin pregnancy via double ET, but also reduce the risk of multiple pregnancy. Therefore, single ET is recommended in women with a unicornuate uterus during IVF-ET.