Nutritional services during pregnancy and birthweight: a retrospective matched pair analysis.

Since 1963, unselected prenatal patients at the Royal Victoria Hospital, Montreal, have been given nutritional counselling and, if it was judged necessary, dietary supplementation by the Montreal Diet Dispensary. From uniform data collected for all obstetric patients in 1963--74, 1213 recipients of the dispensary services (89.7% of those available and eligible for matching) were paired with controls matched for date of delivery (within 12 months), religious affiliation, parity, trimester of pregnancy during which prenatal care was begun and weight at the time of conception. The proportion of infants of low birthweight (less than 2500 g) was 5.7% for the recipients and 6.8% for the controls; the difference was not significant, but the recipients' infants were heavier at birth than the controls' infants, by an average of 40 g (P less than 0.05). The difference in birthweight was greatest for the infants of women in their first pregnancy (average 61 g) and least for the infants of women with three or more past deliveries (average 9 g). Increased birthweight (by an average of 53 g, P less than 0.02) among the recipients' infants was limited to those born to women weighing less than 140 lb (63 kg) at the time of conception; among the heavier women the controls had infants who were heavier, but not significantly so. Differences between the groups in duration of gestation and maternal weight gain accounted for only a small part of these differences in birthweight. This study provides evidence that the Montreal Diet Dispensary program significantly increased birthweight. Further efforts must now be directed towards judging the long-term benefit of these changes.