Case-control study of caffeinated beverages and preterm delivery.

Although many women reduce their caffeine consumption once they known they are pregnant, 70-80% of pregnant women still consume caffeine. To evaluate the relation between caffeine consumption and preterm delivery, a case-control study was conducted to identify all preterm (< 37 weeks gestation) infants born to women in selected North Carolina counties from September 1988 through April 1991. Randomly selected full-term, normal-weight livebirths (matched by race and hospital) served as controls. The study population consisted of 408 cases and 490 controls. Telephone interviews with participants assessed the consumption of caffeinated coffee, tea, cola soft drinks, and noncola caffeinated soft drinks, with caffeine consumption measured by the number of daily servings of each beverage and the total milligrams of caffeine. Third-trimester caffeine consumption from all beverages combined showed a nonsignificant inverse association with preterm delivery. Both first- and second-trimester consumption of 1-150 mg/day were associated with a modestly increased risk of preterm delivery, while no association was found at higher consumption levels. Overall, these results do not support an association between caffeinated beverage consumption and preterm delivery, as is true in most previous studies.