Fetal Heart Rate Response to Maternal Exertion

Marshall W. Carpenter, Stanley P. Sady, Bente Hoegsberg, Mina A. Sady, Barbara Haydon, Eileen M. Cullinane, Donald R. Coustan, Paul D. Thompson

Research output: Contribution to journalArticlepeer-review

89 Scopus citations


Doppler monitoring of fetal heart rates during maternal exertion has suggested that fetal bradycardia occurs frequently during vigorous exercise, causing concern for fetal safety. Doppler determination of fetal heart rate during vigorous maternal effort is difficult. To avoid motion artifact, we observed fetal heart rate using two-dimensional ultrasound and determined the incidence of fetal bradycardia in 45 pregnant women (age, 29.0±3.7 years [mean ± SD]; gestational age, 25.2 ± 3.0 weeks) during 85 submaximal and 79 maximal cycle ergometer tests. Average fetal heart rate did not change during exercise. A single episode of fetal bradycardia (heart rate <110 beats per minute for ≥10 s) occurred during submaximal exertion during a maternal vasovagal episode. Sixteen episodes of fetal bradycardia were noted within three minutes after cessation of exercise, 15 of which followed maximal maternal effort. We conclude that brief submaximal maternal exercise up to approximately 70% of maximal aerobic power (maternal heart rate ≤148 beats per minute) does not affect fetal heart rate. In contrast to submaximal maternal exertion, maximal exertion is commonly followed by fetal bradycardia. This may indicate inadequate fetal gas exchange.

Original languageEnglish (US)
Pages (from-to)3006-3009
Number of pages4
JournalJAMA - Journal of the American Medical Association
Issue number20
StatePublished - May 27 1988
Externally publishedYes

ASJC Scopus subject areas

  • Medicine(all)


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