Determinants of size at birth in a Canadian population.

Anthropometric, medical, and sociodemographic characteristics and smoking habit of a random sample of postpartum women in a Canadian population were determined. These characteristics were analyzed in relation to the birth size of their babies. With controls for gestational age and fetal sex, the following maternal variables were positively correlated with birth weight: prepregnant weight, weight gain in pregnancy, stature, bicristal and biacromial diameter, calf and upper arm circumference, and triceps and subscapular skinfold thickness. Smoking during pregnancy reduced birth weight by 13 gm per cigarette smoked daily. Similar associations of maternal size and smoking habit were observed with respect to infant length, head circumference, and chest circumference. The predictors of birth weight are proposed for use in adjusting upward or downward the population distribution of birth weight to reflect the individual characteristics of the mother.