Birth order and sexual orientation in women

One of the world's largest databases on human sexuality was used to investigate whether lesbians, like homosexual men, have a later birth order relative to heterosexual comparisons. The women (N > 5,000) were interviewed by investigators at the Kinsey Institute for Sex and Reproduction from 1938 to 1963. The women were dichotomously classified as lesbian (n = 257) or heterosexual(n = 5,008). No significant birth order effect was observed. Results support theories of gender-specific mechanisms in the development of sexual orientation in women and men.