Does participation in prenatal courses lead to heavier babies?

In a prospective epidemiologic survey of 1,676 primiparous women delivering in four Montreal hospitals during an eight-month period, we studied the impact of prenatal courses on birthweight, maternal weight gain, and cigarette smoking. Women who participated in prenatal courses were older and of higher socioeconomic status and were less likely to be smokers than non-participants. After adjustment for these differences, newborns of course participants had similar mean birthweights compared to those of non-participants (3286 grams vs 3271 grams), and the difference for maternal weight gain was substantially reduced. Most of the reduction in cigarette consumption occurred during the first three months of pregnancy, even among later participants, suggesting that something other than prenatal courses influenced cigarette smoking reduction in course participants. We conclude that as far as the birthweight objective is concerned, the format and content of prenatal courses (as currently constituted in the Montreal region) require re-examination, and new ideas and interventions need to be developed and tested.