The impact of infertility on family size in the USA: data from the National Survey of Family Growth.

BACKGROUND Investigators have postulated that family size may be influenced by biologic fertility potential in addition to sociodemographic factors. The aim of the current study is to determine if a diagnosis of infertility is associated with family size in the USA. METHODS We analyzed data from the male and female samples of the 2002 National Survey of Family Growth using multivariable logistic regression models to determine the relationship between infertility and family size while adjusting for sociodemographic and reproductive characteristics. RESULTS In the survey, 4409 women and 1739 men met the inclusion criteria, of whom 10.2% and 9.7%, respectively, were classified as infertile, on the basis of having sought reproductive assistance. Infertile females had a 34% reduced odds of having an additional child compared with women who did not seek reproductive assistance. For each additional 6 months it took a woman to conceive her first child, the odds of having a larger family fell by 9% and the odds of having a second child were reduced by 11%. A diagnosis of male infertility reduced the odds of having a larger family more than a diagnosis of female infertility. CONCLUSIONS A diagnosis of infertility, especially male factor, is associated with reduced odds of having a larger family, implicating a biologic role in the determination of family size in the USA.