Effects of dietary lead and zinc on pregnancy.

In order to further understand the effects of ingested Pb on pregnancy and the possible interaction of the trace element Zn with Pb, groups of dated pregnant rats were fed 10, 50, 100, 200, or 500 mg/L of Pb in water throughout pregnancy. A control group with no Pb, but diet ad lib, and a pair-fed control group with no Pb were also studied. Maternal average daily food consumption was significantly reduced at 50 mg/L of Pb and up. Total and net maternal weights were significantly reduced at 50 mg/L of Pb and up. Pair feeding at the 200 mg/L level improved maternal weight gain but not to control levels. Zn, 200 mg/L, supplement at the 200 mg/L of Pb level caused no improvement nor did ad lib diet with Pb removed after 16 days. Fetal weight decreased progressively as Pb levels were increased. Pair feeding at the 200 mg/L Pb of level and Zn, 200 mg/L, supplement with 200 mg/L of Pb significantly increased fetal weight but not to control levels. Placental weight was unchanged throughout. The results indicate that Pb-induced fetal growth retardation is due to reduced maternal food and energy intake, as well as to direct effect on the fetus. Excess dietary Zn improves fetal growth, probably by increasing maternal food consumption.