OBJECTIVE: To evaluate the effect of intracytoplasmic sperm injection (ICSI) and male factor infertility on the sex ratio in births from assisted reproductive technology. DESIGN: Historic cohort study. SETTING: Clinic-based data. PATIENT(S): The study population included 15,164 singleton live births in the Society for Assisted Reproductive Technology national database for 2005 from cycles using ejaculated sperm, categorized by the use of insemination or ICSI and the absence or presence of male factor infertility, and cleavage- versus blastocyst-stage embryo transfers (ETs). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The probability of a male infant with and without the use of ICSI and in the presence or absence of male factor infertility. RESULT(S): The sex ratio for all U.S. live births in 2005 was 52.5%, versus 48.9% for cleavage-stage and 51.6% for blastocyst-stage embryos. With blastocyst-stage embryos, the sex ratios were 49.6% and 54.9% with and without ICSI and 52.6% and 50.0% with and without male factor infertility, respectively. With cleavage-stage embryos, the sex ratio was not significantly affected by ICSI or male factor infertility, singly or in combination. CONCLUSION(S): The use of ICSI, particularly with blastocyst-stage embryos, is associated with a decrease in the sex ratio of male infants.
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