Pregnancy outcome in North American women. I. Effects of diet, cigarette smoking, and psychological stress on maternal weight gain

This study examined the roles of diet, cigarette smoking, and psychological stress in pregnancy weight gain. The 60 subjects were selected by defined criteria to minimize variation in anthropometric, socioeconomic, and medical variables which also affect weight gain. To maximize variation in weight gain, subjects were also selected on the basis of low weight gain (≤15 lb) and adequate weight gain (>15 lb). Each weight gain group contained smokers and nonsmokers. Smokers consumed more calories than nonsmokers (2119 versus 1810 kcal/day. p < 0.01). For nonsmokers. differences between the intakes of low weight gain (1617 kcal/day) and adequate weight gain (1905 kcal/day) women were significant (p < 0.02) and calorie intake was correlated with weight gain (r = 0.44, p < 0.02). Psychological stress negatively correlated with weight gain (r = 0.37, p < 0.01) but not with calorie intake. We conclude that low weight gain is associated with a lower food intake. In contrast, smoking and stress may cause low weight gain by reducing the utilization of calories for weight gain.