Very high collagen increase in placentae of smoking mothers.

In 55 placentae, collected at term from clinically normal pregnancies, hydroxyproline was assayed. Thirty were from mothers who smoke and 25 from nonsmokers. In placentae of smokers, hydroxyproline concentration was 42.77 +/- 8.77 micrograms/mg of tissue and in these of nonsmokers 22.52 +/- 7.46 micrograms/mg. Such high a difference discloses a large increment in placental collagen production in smokers, which may account for some of the noxious effects of tobacco on pregnancy.