Does selenium reduce the risk of threatened preterm delivery associated with placental cytochrome P450-1A1 activity?

Selenium (Se), an essential trace element in human nutrition, is thought to have an important role in the prevention of oxygen damage by organic hydro peroxides generated by oxidative metabolism. Epidemiological studies have s hown an association between placental cytochrome P450-1A1 (CYP1) activity a nd threatened preterm delivery (TPD), and other experimental studies have s hown alterations in fetal development with (CYP1) activity or toxicity. The present study examined the possible protective effect of selenium on the p otential toxicity of maternal exposure to polycyclic aromatic hydrocarbons (PAHs) on the normal course of pregnancy. Placental CYP1 activity was used as a risk factor resulting from maternal exposure to PAHs. TPD occurrence w as used as a general indicator of troubles in the normal course of pregnanc y. A group of TPD patients and a group of controls were selected A om 178 p regnant women attending obstetrical care in a maternity hospital. Selenium concentrations in maternal plasma were lower in the TPD group: 63.7 ng/ml ( CI95% confidence bounds = 43.6-82.2) vs 69.2 ng/ml (CI95% confidence bounds = 49.3-96.3) (t test, P< 0.01). When placental CYP1 was induced, an associ ation between TPD and selenium was found, with an increase of 10 ng/ml for the latter. An adjusted odds ratio of 0.55 (CI 95% confidence bounds = 0.34 -0.88; <chi>(2), P< 0.01) was estimated. When placental CYP1 was not activa ted, the odds ratio was estimated at 0.99 (CI 95% confidence bounds = 0.95- 1.03; NS). This epidemiologic finding suggests that antioxidant Se status m ay be a protective factor against the potential toxic effect of PAHs on the normal course of pregnancy. The downward trend that me observed supports t he hypothesis that the one-electron pathway metabolism of PAHs may explain a large fraction of TPD and some preterm deliveries. :(C) 2000 Academic Pre ss.