| Sumario: | Little data exist regarding the acute maternal and fetal cardiovascular effects of caffeine ingestion. The purpose of this study is to assess the cardiovascular effects of caffeine ingestion in pregnant subjects and their fetuses. We examined seven caffeine-naive gravidas longitudinally at 25.7 (SE + or - 0.7) and 36.1 (+ or - 0.7) weeks' gestation, before and after ingestion of a caffeine citrate solution (100 mg/m to the minus second power body surface area). Maternal pulse, blood pressure, fetal heart rate, and fetal heart rate accelerations were determined before and after caffeine ingestion. Uterine artery, fetal aorta, and umbilical artery flow velocity waveforms were examined at similar intervals. Significant before and after caffeine differences, regardless of gestational age, were noted for maternal pulse (85.1 vs 74.2 beats/min), diastolic blood pressure (65.9 vs 73.8 torr), mean arterial blood pressure (81.5 vs 87.5 torr) uterine artery systolic-to-diastolic (S/D) ratio (1.9 vs 2.4) fetal heart rate (144.6 vs 135.4 beats/min), and fetal heart rate accelerations (1.6 vs 4.2 per 30 minutes). Differences for fetal aortic and umbilical artery S/D ratios were not significant with respect to caffeine administration. Fetal aortic peak velocities increased with caffeine (85.5 vs 130.2 cm/sec) and the increase was augmented with advancing gestational age. We conclude that maternal ingestion of modest amounts of caffeine citrate in caffeine-naive subjects significantly affects both the fetal and maternal cardiovascular systems. Caffeine (1,3,7-trimethylxanthine) is commonly found, either occurring naturally or as a food additive, in beverages, foods, and over-the-counter medications. The average person in the United States consumes about 200 mg of caffeine per day, primarily in the form of coffee (brewed coffee, average caffeine content 88 mg per serving). Consumption during pregnancy varies little from this average. Caffeine clearance during pregnancy gradually decreases, so that by the third trimester elimination has declined threefold from the nonpregnant rate, which may lead to a greater exposure for a given dose. Fetal plasma levels rapidly equilibrate with maternal levels because caffeine is highly lipid soluble and rapidly crosses the placenta. Animal models demonstrate adverse fetal outcomes associated with chronic caffeine exposure, but case-control and cohort studies with human fetuses have yielded conflicting results. The cardiovascular effects of this drug have been well described in nonpregnat individuals, but few studies address the maternal and fetal cardiovascular responses to acute caffeine ingestion. Given the altered maternal physiology and the unique cardiovascular responses of the fetus, the effects of this drug may differ greatly and potentially impact on the maintenance of normal maternal-fetal homeostasis. The purpose of this study is to assess the acute maternal and fetal cardiovascular effects of caffeine ingestion in healthy gravidas not accustomed to caffeine intake.
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