Comparison of early pregnancy and neonatal outcomes after frozen and fresh embryo transfer in ART cycles
OBJECTIVE To describe patterns of preterm birth and low birth weight (LBW) for infants born after assisted reproductive technology (ART) and determine whether these were associated with maternal or treatment characteristics. DESIGN Retrospective cohort study of national population data of infants conceived through ART. SETTING Australian birth records from 1996 to 2000. PATIENT(S) Eighteen thousand, four hundred twenty-nine liveborn and stillborn infants conceived through ART. INTERVENTION(S) In vitro fertilization, intracytoplasmic sperm injection, and gamete intrafallopian transfer. MAIN OUTCOME MEASURE(S) Preterm birth and LBW. RESULT(S) Preterm birth and LBW were more common among singletons and twins conceived with IVF and born to nulliparous mothers. Preterm birth and LBW were, respectively, 1.3 times and 1.5 times more likely to occur among singletons conceived by transfer of fresh embryos, compared with transfer of frozen embryos. Preterm birth and LBW was more common among couples who had female-factor infertility compared with male-factor infertility. CONCLUSION(S) The transfer of fresh embryos and female-factor infertility were independently associated with preterm birth and LBW for both singletons and twins after ART.