ABSTRACT
Little data exist regarding the acute maternal and fetal cardiovascular effects of
caffeine ingestion. The purpose of this study is assess the cardiovascular effects
of caffeine ingestion in pregnant subjects and their fetuses. We examined seven caffeine-naive
gravidas longitudinally at 25.7 (SE ± 0.7) and 36.1 (± 0.7) weeks' gestation, before
and after ingestion of a caffeine citrate solution (100 mg/m2 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.
