Objective: To determine the fetal response to and safety of maximal materna
l exercise in the third trimester.
Methods: Twenty-three active women with uncomplicated pregnancies (singlet-
on gestations) underwent maximal exercise testing in late gestation using a
progressive maximal cycle ergometer protocol. Fetal heart rate (FHR) respo
nses were monitored and classified using National Institute of Child Health
and Human Development guidelines. Statistical analyses involved use of the
Student t test repeated measures analysis of variance with Tukey-Kramer mu
ltiple comparisons posttest, and the chi(2) test.
Results: There was an increase in baseline FHR in the 20-minute posttest pe
riod compared with the 20-minute pretest period. There were significantly f
ewer accelerations in the second posttest 10-minute segment compared with t
he second pretest 10-minute segment. Variability was reduced in both postte
st periods compared with the first 10-minute pretest period. Time to reacti
vity increased after testing. Mild tachycardia was noted in two tracings an
d bradycardia occurred in a fetus with previously undiagnosed growth restri
ction. There were no abnormal neonatal outcomes.
Conclusion: Maximal exercise testing in late gestation led to minimal chang
es in FHR. Fetal bradycardiac responses were not seen in appropriate for ge
stational age fetuses, suggesting that brief maximal maternal exertion for
research or diagnostic purposes is safe in this group. (Obstet Gynecol 2000
;96;565-70. (C) 2000 by The American College of Obstetricians and Gynecolog
ists.).