[Effects of lead administered during pregnancy to C57B1 mice].

Treatment of female mice with high doses of lead from different times of the gestation, induces abortion or retardation of growth of the embryos. When it is given from birth, it provokes important mortality in the youngs and a retardation of the postnatal growth. In most cases, lead administered from the first day of gestation delays slightly the development of the embryo and inhibits its implantation. It seems that a deficiency in the plasmatic progesterone levels is directly implied in this inhibition.