Stress hormones and placental steroids in physical exercise during pregnancy.

The hormonal responses to exercise during later pregnancy were studied in relation to an exercise test in ten healthy women. At the end of the 10-min exercise, maternal heart rate had risen from 93 +/- 3.2 (mean +/- SEM) to 157 +/- 6.3 beats/min, and systolic blood pressure from 120 +/- 3.4 to 148 +/- 5.4 mmHg, but diastolic blood pressure was unchanged. Plasma concentrations of noradrenaline and adrenaline rose rapidly during the exercise, from 2.9 +/- 0.3 to 6.9 +/- 1.2 nmol/l and from 0.31 +/- 0.04 to 0.47 +/- 0.08 nmol/l respectively. The serum concentration of prolactin did not change during the test, but 30 min after the exercise the value had risen from 146 +/- 17 to 212 +/- 22 mg/ml, thereafter slowly declining. The serum concentration of cortisol remained unchanged. The mean concentration of oestriol rose from 31.5 +/- 2.6 to 33.9 +/- 3.0 nmol/l at least 5 min after the exercise, thereafter declining to 29 +/- 2.6 nmol/l. After the test, levels of progesterone and oestradiol also fell slightly. Mild irregular uterine activity was found in four subjects. Cardiotocography revealed a transient fetal tachycardia in two subjects.