Blastocyst versus day-3 embryo transfers: A comparison of fresh and thaw cycle cumulative outcomes

Abstract

Objective: A number of strategies have been designed to reduce multiple gestation rates while enhancing pregnancy and delivery rates. One method is to transfer two day-3 embryos and utilize supernumerary embryos in subsequent thaw cycles. An alternative strategy is to transfer two blastocyst stage embryos after extended culture to day 6 in vitro. The goal of the present study is to examine the cumulative pregnancy outcomes of fresh plus thaw cycles derived from a single oocyte retrieval in patients in whom two day-3 embryos were transferred and compare this data to cumulative outcomes when two blastocyst-stage embryos were transferred. Design: Retrospective analysis. Materials/Methods: Cycles in patients aged less than 35 years who underwent oocyte retrieval and day 3 transfer (D3T) or blastocyst transfer (BT) of two embryos between May 1, 1999 and October 31, 2001 were included in the study. Clinical pregnancy, live birth, singleton delivery, and multiple delivery rates were calculated for D3T and BT cycles. Cumulative pregnancy outcomes were determined by combining the outcomes of fresh cycles with outcomes of subsequent thaw cycles derived from the same ovulation induction/oocyte retrieval cycle. Data was examined by chi-square analysis. Results: During the study period, there were 527 fresh D3T cycles in which two embryos were transferred and patient age was less than 35 years. In fresh cycles only, the clinical pregnancy rate was 44.8% (236/527) and the live birth delivery rate was 31.1% (164/527). In 318 cycles (60.3%) at least one day-3 embryo was cryopreserved. 168 (31.8%) subsequent thaw cycles were performed. Combining fresh and thaw cycle outcomes revealed a cumulative pregnancy rate per oocyte retrieval of 50.5% (266/527). The cumulative live birth rate was 32.8% (173/527). 30 of 266 pregnancies (11.3%) were the result of thaw cycles. In the 188 fresh BT cycles examined, the pregnancy rate was 34.0 % (64/188) and the live birth rate was 29.8% (56/188). 23 (12.2%) subsequent thaw cycles were performed. The cumulative clinical pregnancy rate was 36.2% (68/188) and the cumulative live birth rate was 30.3 % (57/188). 4 clinical pregnancies and 1 live birth were the result of thaw BT cycles. Comparison of cumulative D3T and BT pregnancy, delivery, and multiple pregnancy rates are summarized in Table 1. Table 1Cumulative Pregnancy OutcomesAverage age, yearsPregnancy rate, %Live birth rate, %Singleton, %Twin, %Triplet, %Day-331.350.5 (266/527)∗p < 0.00132.8 (173/527)69.4 (120/173)28.3 (49/173)1.2 (1/173)Blastocyst31.836.2 (68/188)30.3 (57/188)68.4 (39/57)31.6 (18/57)0∗ p < 0.001 Open table in a new tab Conclusions: Among patients younger than 35 years of age, the cumulative live birth rate achieved by transfer by two fresh day-3 embryos combined with subsequent thaw cycles is comparable to cumulative cycle outcomes when two blastocyst-stage embryos are transferred. Additionally, the multiple gestation rates are similar. The significantly higher pregnancy rate of cumulative day-3 cycles is minimized by an increased rate of miscarriage in day 3 transfers. These data indicate that day-3 and blastocyst transfer of two embryos are expected to yield similar cumulative live birth rates with similarly low multiple gestation rates in this population.