DDT and DDE exposure in mothers and time to pregnancy in daughters

Reproductive-tract anomalies after administration of the potent oestrogen, diethylstilboestrol, in pregnant women raised concerns about the reproductive effects of exposure to weakly oestrogenic environmental contaminants such as bis[4-chlorophenyl]-1,1,1-trichloroethane (p, p′-DDT) or its metabolites, such as bis[4-chlorophenyl]-1,1-dichloroethene (p, p′-DDE). We measured p, p′-DDT and p, p′-DDE in preserved maternal serum samples drawn 1–3 days after delivery between 1960 and 1963. We recorded time to pregnancy in 289 eldest daughters 28–31 years later. Daughtersʹ probability of pregnancy fell by 32% per 10 μg/L p, p′-DDT in maternal serum (95% CI 11–48). By contrast, the probability of pregnancy increased 16% per 10 μg/L p, p-DDE (6•27). The decreased fecundability associated with prenatal p, p′-DDT remains unexplained. We speculate that the antiandrogenic activity of p, p -DDE may mitigate harmful androgen effects on the ovary during gestation or early life.