Fecundity and sex ratio of offspring in an infertile cohort

Objective To determine whether male and female subfecundity is associated with the gender ratio. Design Retrospective cohort study. Setting Reproductive endocrinology clinics in California. Patient(s) A cohort of 30,448 women who sought infertility treatment or evaluation in California between 1990 and 1998 was identified. A fertile comparison group was assembled after matching data from vital statistics records. Intervention(s) Not applicable. Main Outcome Measure(s) Multivariate logistic regression was used to determine the odds of a male birth based on fertility status. Result(s) We identified 5,293 infertile women and 6,730 fertile matched women in the live-birth and fetal death records. There were 6,178 children born to women evaluated and/or treated for infertility, compared with 9,131 born to fertile women, for a total of 15,309 births. There was no significant difference in the secondary sex ratio between births in the infertile cohort and the fertile cohort or on the basis of male factor infertility versus female factor infertility. After controlling for confounding factors, there was no difference in sex ratio based on the use of advanced reproductive technologies, duration of infertility treatment, or the type of infertility. Conclusion(s) This study found no statistical evidence to support an association between infertility and secondary sex ratio.