Maternal caffeine consumption and fetal behavior in normal third-trimester pregnancy

Our aim was to perform a longitudinal cohort study of 20 normal third-trimester pregnancies to observe whether the level of long-term maternal caffeine ingestion influenced fetal behavior.

By dietary history 10 normal pregnant women were categorized as "high" caffeine consumers (> 500 mg/day, group H) and 10 as "low" caffeine consumers (> 200 mg/day, group L). Between 30 and 40 weeks biweekly 2-hour continuous ultrasonographic observations of fetal heart rate; breathing activity; and eye, trunk, and extremity movements were conducted. Maternal caffeine levels were determined at each session, and fetal states were identified and their duration quantified. Data were compared by analysis of variance by means of repeated measures or t tests.

When compared with group L fetuses, group H fetuses spent similar mean time in state 1F (quiet sleep), less mean time in state 2F (active sleep), and much greater mean time in state 4F (arousal). The mean time spent in no state decreased significantly in group L, was unchanged in group H, and was similar for both groups at term. Both groups had similar mean numbers of state changes at all gestational ages studied. Mean maternal serum caffeine levels in group H were always significantly higher than those in group L.

Evolving fetal behavior may be influenced by the level of maternal caffeine consumption during the last trimester.