Caffeine-cigarette interaction on fetal growth.

The influence of caffeine and cigarette consumption on fetal growth during pregnancy was studied retrospectively in 913 newborn infants. Analysis of variance was adjusted for length of gestation and sex. A significant caffeine-cigarette interaction was found on birth weight (F = 85.4, p less than 0.01). Among women smoking 15 cigarettes or more per day, birth weight was 206 gm (+/- 57.7 gm) lighter for babies whose mothers consumed 300 mg or more of caffeine per day. Head circumference and length of the newborns were affected only by cigarette smoking. Another caffeine-cigarette interaction was observed on placental weight (F = 15.0, p less than 0.01). Among women who consumed less than 300 mg of caffeine daily, placental weight increased with cigarette consumption. However, it diminished (p less than 0.05) among women smoking 15 cigarettes or more per day if they consumed 300 mg or more of caffeine daily. This is the first time that such interactions were found to influence birth and placental weights, indicating that the concomitant consumption of caffeine and cigarette constitutes a higher risk for the developing fetus.