Trends and correlates of the sex distribution among U.S. assisted reproductive technology births
Article In Press
Jennifer L. Narvaez, M.D., Jeani Chang, Ph.D., M.P.H., Sheree L. Boulet, Dr.P.H., M.P.H., Michael J. Davies, Ph.D., M.P.H., Dmitry M. Kissin, M.D., M.P.H.
To assess national trends in the sex distribution of live-born infants in the assisted reproductive technology (ART) and general population and to identify factors correlated with offspring sex.
Retrospective cohort study.
Fertility treatment centers.
All live-born infants included in the National Vital Statistics System and resulting from ART cycles reported to the National ART Surveillance System during 2006–14.
Main Outcome Measure(s)
Trends in the proportion of male infants in the general population and proportion of males from fresh ART cycles among all ART live-born infants and singletons after single ET.
There were 214,274 live-born infants resulting from fresh ART cycles; 53.5% (5,492/10,266) of infants resulting from PGD/PGS cycles were male, as compared with 50.6% (103,228/204,008) in the non-PGD/PGS group. Among non-PGD/PGS cycles, blastocyst transfer was positively associated with male infants (adjusted risk ratio [aRR] = 1.03; 95% confidence interval [CI], 1.02–1.04). Intracytoplasmic sperm injection was negatively associated with male infants (aRR = 0.94; 95% CI, 0.93–0.95) and for singletons after single ET (aRR = 0.93; 95% CI, 0.90–0.95), as was transfer of two embryos (aRR 0.98; 95% CI, 0.97–0.99) or three or more embryos (aRR = 0.98; 95% CI, 0.96–0.99) among all live births from cycles without PGD/PGS use.
The proportion of male live-born infants among ART population did not change during 2006–14, ranging from 50.5% to 51.2%. Factors such as blastocyst transfer, intracytoplasmic sperm injection use, embryo stage, and number of embryos transferred may be associated with infant sex; further investigation is needed to understand possible underlying causes.