Active Voice: Exercise Testing Ė A Window into Cardiovascular Health During Pregnancy
By: Victoria L. Meah, Ph.D.

Pregnancy results in profound adaptation of a femaleís cardiovascular system. It is well established that resting heart rate and cardiac output progressively increase over the course of pregnancy. These changes enable the cardiovascular system to meet the demands of the developing baby but, at rest, a motherís heart has a greater workload compared with pre-pregnancy.

Historically, there was a hypothetical concern that exercise during pregnancy may overload a motherís heart. It was suggested that the additional metabolic demand of activity during pregnancy would result in reduced blood flow to the developing fetus. This remains unsubstantiated, and many empirical studies have shown that blood flow to the fetus is maintained during prenatal exercise in healthy individuals. However, far less is known about how a motherís heart responds to exercise.

In our study published in the May 2021 issue of Medicine & Science in Sports & Exerciseģ, we completed cardiovascular assessments in 18 non-pregnant, 14 pregnant (22 to 26 weeks) and 13 postpartum (12 to 16 weeks post-delivery) healthy females at rest and during exercise. The exercise challenges included a submaximal isometric handhold and low-moderate intensity cycling. We used ultrasound imaging via echocardiography to measure heart function and compared the group responses to the exercise challenges. Because of the greater cardiac function at rest in pregnant participants, we accounted for these differences in our statistical comparisons so that we could isolate the exercise responses only. We found that although pregnant participants had higher resting heart rate and cardiac output compared with non-pregnant and postpartum participants, all groups had similar changes in cardiac function in response to exercise. These findings show that mothersí hearts have proportionate responses to submaximal exercise during pregnancy and further validate the safety of prenatal physical activity within current ACSM recommendations.

This study provides important information about how the heart copes with both pregnancy and exercise. It also acts as a foundation for future research into the value of exercise testing in pregnancy. In other populations, blunted or exaggerated responses during an exercise test can identify those with high risk of cardiovascular disease, even if their resting cardiac function is normal. Early identification of heightened risk in individuals allows for proactive management. This may include increased medical monitoring and/or encouragement to make positive lifestyle changes such as increasing physical activity, nutritional interventions or reducing stress. Proactive management could delay the progression and/or reduce the severity of cardiovascular disease.

Pregnancy is a cardiovascular stress test. Although most adapt well to pregnancy, some individuals develop serious cardiovascular complications, such as preeclampsia, in the latter half of gestation when the cardiac workload peaks. Preeclampsia can have serious consequences to both a motherís and infantís short- and long-term health. As such, ways to reduce the impact of this complication are desperately needed. We suggest that exercise testing completed early in pregnancy may identify those at risk for a cardiovascular complication before it becomes a burden on their health. These individuals could then be proactively managed to improve outcomes for both mom and baby.

There are several important yet unanswered questions regarding the value of exercise testing during pregnancy. As a starting point, this study has shown what a healthy response to exercise is, but future studies are needed to determine what abnormal cardiovascular responses are and whether these predict the later development of complications during pregnancy.

About the author:
Victoria L. Meah, Ph.D., is a Canadian Institute of Health Research-funded postdoctoral fellow in the Program for Pregnancy and Postpartum Health at the University of Alberta. She is also the recipient of a postdoctoral fellowship funded by the generosity of the Alberta Womenís Health Foundation through the Women and Childrenís Health Research Institute. Dr. Meah obtained her doctorate from the School of Sport and Health Sciences at Cardiff Metropolitan University. She studies the influence of physical activity on cardiovascular health during pregnancy. Dr. Meah is a member of the ACSM Pregnancy and Postpartum Special Interest Group steering committee, a BASES-accredited Certified Exercise Practitioner and a member of the Active Pregnancy Foundation Scientific Advisory Board. Connect with her on Twitter @vtorixm or by email at vmeah@ualberta.ca.

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