Maternal smoking and low birthweight in the reproductive history of women in Puerto Rico, 1982.

In 1982, a representative sample of 3,175 women ages 15 to 49 years living in Puerto Rico were interviewed and complete reproductive histories obtained. Births to mothers who started smoking regularly at some time before delivery and who were still smoking at the time of the interview (the exposure definition) were compared with unexposed births. Our analysis of 4,444 single, live births delivered in public and private hospitals from 1946 through 1982 demonstrates that births to smoking women aged 20 and older delivering in public hospitals were 2.5 times more likely to weigh less than 2,500 grams (95% confidence interval (CI) = 1.9, 2.3), and on the average weighed 207 grams less (95% CI = 130, 284) than births to a comparable group of nonsmoking mothers. However, we found no other difference in birthweight between newborns of smoking and nonsmoking women when comparing their births within the same hospital category and age group. The data in this study suggest that the effect of smoking on birthweight among births to Puerto Rican women may be modified by maternal age and by whether the infant was born in a private or public hospital.