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By William C. Haas III, MD, MBA
Integrative Medicine Fellow, Department of Family and Community Medicine, University of Arizona, Tucson
Dr. Haas reports no financial relationships relevant to this field of study.
SYNOPSIS: Regular exercise throughout pregnancy exhibits a protective effect against the development of hypertension and excessive gestational weight gain without increasing the incidence of low birthweight infants.
SOURCE: Barakat R, et al. Exercise during pregnancy protects against hypertension and macrosomia: Randomized clinical trial. Am J Obstet Gynecol 2015 Dec 15; doi: 10.1016/j.ajog.2015.11.039. [Epub ahead of print].
Hypertensive disorders are some of the leading causes of maternal and fetal morbidity and mortality.1,2 The precise mechanism for elevated blood pressure during pregnancy is not yet known; however, excessive gestational weight gain (GWG) and maternal obesity have been strongly correlated with developing a hypertensive disorder (i.e., gestational hypertension, pre-eclampsia).3,4
Implementing interventions to minimize excessive GWG have been recommended to reduce perinatal complications, including hypertension. Retrospective studies suggest that women engaging in regular exercise have a reduced risk of developing pregnancy-induced hypertension and pre-eclampsia.5,6 In an effort to strengthen the evidence for physical activity in pregnancy, a group of researchers recently conducted a randomized, controlled trial evaluating the effect of exercise on pregnancy-induced hypertension as well as excessive GWG. Secondary outcomes included the incidence of infant macrosomia and low birthweight.
Based on calculations from a power analysis, 1100 pregnant women were recruited for the study. Inclusion criteria included women with singleton pregnancies and no history of diabetes mellitus (type 1, type 2, or gestational). After applying exclusion criteria (history of preterm delivery, contraindications to exercise, or plans to deliver at a hospital not associated with the study), 840 patients were identified and equally randomized to an exercise intervention or standard care.
The exercise intervention consisted of group training sessions (10-12 participants) that occurred 3 days/week for 50 minutes starting in the first trimester and continuing until delivery. Each session involved aerobic exercise, light resistance training, and stretching. The control group was given general advice about the positive effects of physical activity and questioned regarding their level of physical activity each trimester. Blood pressure was measured at every visit using a standardized protocol. Total GWG was calculated using the weight at the last clinic visit before delivery minus the pre-pregnancy weight. Birth weight was recorded from hospital perinatal records and classified according to standard definitions (macrosomia, > 4000 g; low birthweight, < 2500 g).
A similar number of patients completed the exercise (n = 383) and control interventions (n = 382). No statistical differences were noted between the groups at baseline. With regard to blood pressure, women who did not engage in formal exercise were three times more likely to develop hypertension during pregnancy compared to exercisers (odds ratio [OR], 2.96; 95% confidence interval [CI], 1.29-6.81; P = 0.01). Non-exercisers were also 1.5 times more likely to gain excessive weight compared to exercisers (OR, 1.47; 95% CI, 1.06-2.03; P = 0.02). Exercise was not significantly correlated with low birth weight at delivery; however, the lack of exercise was significantly correlated with macrosomy (OR, 2.53; 95% CI, 1.03-6.20; P = 0.04).
This study extends findings from correlative studies and suggests incorporating exercise into prenatal care to improve the health outcomes of both mother and child. Specifically, regular exercise during pregnancy can reduce the risk for developing hypertension and excessive gestational weight gain, all without affecting gestational age at birth or the method of delivery. These benefits also occurred without an increased risk for low birthweight among infants.
Although adherence to exercise was high in this study (> 80%), motivation and compliance with exercise always remain important considerations. Interestingly, none of the women in the control group were excluded as a result of self-increased physical activity. An organized and accountable exercise program might be an important requirement to achieve the beneficial effects resulting from regular exercise. Future studies should attempt to identify the minimal effective dose for exercise to maximize adherence.
One of the major limitations of the study was the lack of nutritional assessment. Both the quantity and quality of food ingested can drastically affect health metrics, such as blood pressure and weight. Without a clear record of nutritional information, the relative effect of exercise on the measured outcomes cannot be reliably determined.
Overall, this study should encourage physicians to recommend participation in regularly scheduled, well-supervised exercise programs throughout pregnancy. More specifically, recommendations should incorporate both aerobic and light resistance training for 150 minutes per week.
Financial Disclosure: Integrative Medicine Alert’s executive editor David Kiefer, MD, reports he is a consultant for WebMD. Peer reviewer J. Adam Rindfleisch, MD, MPhil, AHC Media executive editor Leslie Coplin, and associate managing editor Jonathan Springston report no financial relationships relevant to this field of study.