Authors
Cohn, B.A., Cirillo, P.M., Wolff, M.S., Schwingl, P.J., Cohen, R.D., Sholtz, R.I., Ferrara, A., Christianson, R.E., van den Berg, B.J., Siiteri, P.K.

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

Journal
The Lancet. 361(9376):2205-2206. 2003.

Summary
DDT (dichlorodiphenyl trichloroethane) was the first of the chlorinated hydrocarbon insecticides widely used after World War II, primarily due to its effectiveness against insect pests that spread malaria, and lice that transmit typhus. In 1973, the use of DDT was banned in the United States because of the persistence of DDT in the environment. DDT resists degradation by natural biological processes and is accumulated in lipid-rich tissues. In particular, organochlorine pesticides accumulate in maternal blood serum and can pass through the placenta to the developing fetus.

Since DDT is known to mimic estrogenic activity by binding to, and activating estrogen receptors, the authors of the present investigation sought to determine whether DDT could have adverse reproductive effects in the daughters of exposed women. Specifically, Cohn's research team studied the pregnancy rates among women born to mothers who were exposed to DDT. Maternal blood samples, taken from the women shortly after giving birth between 1960 and 1963, were analyzed for DDT and its byproduct, DDE. Since the samples were taken prior to the ban of DDT, all had detectable levels of both contaminants. Information pertaining to the fertility of the women's daughters was obtained via questionnaires. The women's daughters were between the ages of 28 and 31, and they provided information pertaining to their fertility history during those months in which contraception was not used. This information was used to determine "time to pregnancy", or how long it takes a woman to become pregnant when she is not protected by contraceptives. The results of the analysis reveal that women of mothers who had higher levels of DDT took longer to become pregnant during times when contraception was avoided. In particular, for every 10 micrograms of DDT per liter of blood in the mother's blood samples, the chance of pregnancy within a menstrual cycle decreased by one-third. However, the chance of becoming pregnant increased by one-sixth with every 10 microgram per liter increase of DDE. The authors speculate that DDE may exert a protective effect by counteracting DDT. DDE may also block the harmful effects of androgen on the ovary during fetal life or just after birth.

The study by Cohn et al. is the first piece of scientific evidence that DDT can exert long-term reproductive effects in the female offspring of exposed women. The findings support the controversial theory that environmental exposure to pesticides and other contaminants that mimic sex hormones might be contributing to human infertility. The researchers believe that additional work with stored blood samples, modern quantitative chemistry, and health records should aid in determining the adult consequences of fetal environmental exposures.