Gestational Changes in Exercise Capacity in Uncomplicated Singleton Pregnancies

Pregnancy is associated with well-characterized changes to the cardiopulmonary systems, yet few studies have quantified exercise capacity across trimesters in healthy pregnancies.

This study aimed to prospectively assess exercise capacity throughout pregnancy via cardiopulmonary exercise testing (CPET).

Healthy pregnant volunteers underwent ramp-protocol cycle-ergometer CPET in the 1st and 3rd trimesters. Volunteers were followed through delivery to record delivery mode, gestational age at delivery, fetal birth weight, and pregnancy complications. The mean CPET measures were summarized and compared between the 1st and 3rd trimesters with paired t-tests.

A total of 25 pregnant volunteers participated, with a mean age of 31.4 years (SD 3.8). All volunteers had normal baseline echocardiograms (median left ventricular ejection fraction 60%, IQR: 60%-62%). Between the 1st and 3rd trimester, there were no statistically significant differences in the mean peak oxygen consumption (1,804 vs 1,894 mL/min, P = 0.58), mean maximal oxygen uptake at the anaerobic threshold (1,236 vs 1,227 mL/min, P = 0.95), mean O₂ pulse (11.0 vs 11.7 mL/beat, P = 0.39), and mean ventilatory efficiency (minute ventilation/volume of carbon dioxide produced and exhaled by the body per minute slope 31 vs 33, P = 0.28). The mean resting and peak heart rate increased significantly (P < 0.01), whereas the mean maximal voluntary ventilation (105 vs 98, P = 0.004) and hemoglobin concentration (13.0 vs 11.8, P < 0.01) decreased. No complications occurred during the CPETs or during labor and delivery.

Despite the expected changes in hemoglobin and lung capacity, exercise capacity remained unchanged between the 1st and 3rd trimesters of pregnancy in healthy volunteers.