Elective single embryo transfer trends and predictors of a good perinatal outcome--United States, 1999 to 2010.

OBJECTIVE To assess trends in elective single ET and identify factors associated with a good perinatal outcome. DESIGN Retrospective cohort study. SETTING Clinic-based data. PATIENT(S) A total of 886,686 fresh, nondonor cycles reported to the National Assisted Reproductive Technology Surveillance System during 1999-2010, of which 17,166 met criteria for elective single ET. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Rates of elective single ET and good perinatal outcome (term, singleton infant with normal birth weight). RESULT(S) In 2010, elective single ET comprised 5.6% of all fresh transfers, representing an eightfold increase since publication of first guidelines in 2004 recommending elective single ET. Compared with other ETs, elective single ETs were nearly twice as likely to result in a good perinatal outcome (37.1% vs. 18.9%, respectively). Among women using elective single ET, those aged <35 and 35-37 years had a good perinatal outcome (40.2% and 32.5%, respectively). In multivariable, log-binomial analyses, factors positively associated with a good perinatal outcome included male factor infertility, day 5 ET, and having ≥3 supernumerary embryos for cryopreservation. CONCLUSION(S) Between 1999 and 2010, national rates of elective single ET increased. Given the frequency of good perinatal outcomes among women aged 35-37 years, guidelines for elective single ET could be expanded to include patients in this age group with favorable prognoses.