Parental smoking empirically related to pregnancy outcome.

Abstract

A prospective statistical study of 48505 pregnancies was carried out to evaluate the effects of parental smoking on pregnancy. Infants born to smoking mothers were significantly smaller than those of nonsmokers. The difference increased with number of cigarettes smoked/day reaching 213 gm for heavy smokers (over 30). Mean birth weights were essentially the same when grouped according to fathers smoking habit indicating no effect of paternal smoking. In third trimester nonsmoker infants were heavier than the groups mean weight and a progressive decrease in birth weight with increasing maternal smoking was noted. When birth weights according to maternal smoking were grouped by maternal prepregnant weight progressive decreases in infant birth weight were demonstrated with increased smoking excluding the possibility that the decrease was due to maternal body weight. When mothers were grouped as to specific trimester in which they smoked the data suggested that smoking in any trimester decreased birth weight. With maternal smoking prematurity by birth weight rose directly to a significant degree (P .05).