Outcomes of singleton births after blastocyst versus nonblastocyst transfer in assisted reproductive technology.

OBJECTIVE: To compare obstetric and perinatal outcomes of singleton births after assisted reproductive technology (ART) with blastocyst transfer (days 5 to 6) versus nonblastocyst transfer (days 2 to 4).
DESIGN: Retrospective cohort study.
SETTING: Monash IVF. PATIENT(S): 4,202 women who conceived using in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) between 2004 and 2009. INTERVENTION(S): Records analysis of fresh and frozen-thawed embryo transfers resulting in singleton births of at least 20 weeks' gestation. MAIN OUTCOME MEASURE(S): Perinatal outcomes: preterm birth, low birthweight, very low birthweight, small for gestational age, large for gestational age, preeclampsia, antepartum hemorrhage, placental abruption, placenta previa, and postpartum hemorrhage; and covariates: maternal age, year of birth of the baby, private health insurance status, maternal body mass index, smoking status, parity, gender of baby, and variations in treatment procedures. RESULT(S): Multivariate analysis found no statistically significant difference between transfers on days 5 and 6 and days 2 and 4 for all maternal and perinatal outcomes. There were modest increases in the adjusted odds ratios for preeclampsia (adjusted odds ratio 1.72, 99% confidence interval 0.93-3.20) and placenta previa (1.65, 0.92-2.98). CONCLUSION(S): Obstetric and perinatal outcomes after blastocyst transfer on days 5 to 6 are similar when compared with embryo cleavage-stage transfers on days 2 to 4.