Prolongation of gestation by growth hormone: a confounding factor in the assessment of its prenatal action.

The administration of urified growth hormone to normally nourished pregnant rats prolonged gestation leading to postmaturity of the offspring. The effect explains, in part, the apparent influence of growth hormone on prenatal and early postnatal development and supports the notion that the prenatal action of exogeneous growth hormone is restricted to a therapeutic one under conditions of malnutrition.