The presence of multiple gestational sacs confers a higher live birth rate in women with infertility who achieve a positive pregnancy test after fresh and frozen embryo transfer: a retrospective local cohort

BACKGROUND: After spontaneous conception, the rate of miscarriage is more common in multiple rather than singleton pregnancies. However, the incidence of miscarriage is lower in in-vitro fertilization twin versus singleton pregnancies. Most patients have little understanding of pregnancy outcomes once they achieve a positive pregnancy test. This study investigated the relationship between multiple pregnancy and miscarriage in women with infertility after fresh and frozen embryo transfer. METHODS: Retrospective local cohort study of all consecutive patients undergoing in-vitro fertilization at our institution (n = 1130), fresh or frozen embryo transfer, between January 1, 2008 and December 31, 2012. Patient characteristics (age, body mass index, initial hCG, maximum follicle stimulating hormone levels) and in-vitro fertilization parameters (estradiol levels, eggs retrieved, and endometrial thickness) were collected and statistically analyzed using T-test and Chi-square test (Stata version 10). Linear and logistic regression were used when appropriate. RESULTS: Overall, live birth rate for all cycles was 30.44% and total pregnancy loss was 6.55% - similar for fresh and frozen cycles despite a higher rate of biochemical pregnancies for frozen cycles. Among all pregnant patients, 62.48% had a live birth. Although clinical pregnancy rate was higher for fresh cycles, live birth rates were similar. In pregnancies where multiple sacs were demonstrated on ultrasound, live birth rates were higher despite 31% of patients losing at least one sac. This finding was comparable between fresh and frozen cycles. However, in patients under age 35 and using donor egg, no live birth advantage was seen in patients with multiple sacs. In fact, transferring more than one embryo did not increase live birth rate either. CONCLUSIONS: Despite the many maternal and fetal risks of multiple pregnancies, patients who achieve a positive pregnancy test with fresh and frozen in-vitro fertilization and who have more than one pregnancy sac are more likely ultimately to deliver at least one baby. This finding is true of both fresh and frozen embryo transfer cycles. This pregnancy advantage is not seen in young patients and in patients using donor egg, and single embryo transfer maximizes birth outcomes.