The effects of long- and short-term maternal caffeine ingestion on human fetal breathing and body movements in term gestations

The possible effects of long- and short-term maternal ingestion of caffeine during normal human pregnancy on the breathing and body movements of third-trimester fetuses were studied in 14 patients, selected by a dietary questionnaire, and divided into two equal groups: high consumers (>500 mg/day) (group 1) and low consumers (<250 mg/day) (group 2). All mothers followed a standard study protocol and underwent overnight fasting; studies began with a 30-minute control period, followed by oral administration of 200 mg caffeine, and a 180-minute subsequent observation period with continued maternal fasting. Blood samples for glucose and caffeine were obtained every 30 minutes and continuous recording of fetal breathing and body movements were entered on a microcomputer for off-line analysis. The two groups were similar for all obstetric outcome features. Plasma glucose levels were similar and constant in both groups whereas caffeine levels increased significantly at 60 minutes after administration; mean plasma caffeine levels were significantly higher in group 1 than in group 2 at all intervals. Fetal breathing rates and body movement incidences were similar in both groups before and after caffeine administration. Fetal breathing movement incidence decreased significantly in group 2 but was sustained at baseline levels in group 1 throughout the study. High long-term ingestion of caffeine during pregnancy is associated with higher maternal plasma caffeine levels and fetal breathing activity when compared with low caffeine ingestion. Short-term administration of 200 mg caffeine does not appear to have a significant physiologic impact on these activities.