Risk assessment for physical activity and exercise clearance

Discussion

A systematic and rigorous examination of the literature published between 1982 and 2009 showed that pregnant women without contraindications were at low risk of adverse events during exercise irrespective of physical activity and fitness level before pregnancy. A total of 49 655 hours of exercise were examined to determine the risk of adverse events, identifying the prevalence of both major and minor maternal events, as well as any exercise-related fetal events. Based on the available evidence, the major adverse event rate was calculated to be 1.4 per 10 000 hours of exercise. When including minor events and exercise-related fetal events, the adverse event rate increased to an overall rate of 6.8 per 10 000 hours of exercise.

It is important to note that both calculations are likely conservative. A major event was generally determined from the reporting of reasons for participant dropout; therefore, it is unknown whether a major adverse event was specifically exercise related. Only 1 major adverse event was reported directly following exercise (ie, uterine contractions requiring 72 hours of medical observation). Examples of minor adverse events reported during or following exercise were leg cramps, nausea, and fatigue. We have purposely erred on the side of caution; however, these events could potentially be classified as common “discomforts” of exercise rather than true adverse events. Although rare, the most frequently reported exercise-related adverse event was fetal brady-cardia. In all instances, the event was reported as transient, and fetal heart rate returned to normal following exercise cessation.

Rates of adverse events must be interpreted in the context of general prescreening for absolute and relative contraindications to exercise, as well as qualified exercise professionals in the environment. The above rates are based on women presenting without contraindications and, accordingly, screening procedures to exclude at-risk pregnant women from participation were administered in most exercise studies reviewed (eg, completion of the Physical Activity Readiness Medical Examination for Pregnancy). Many investigations also evaluated exercise in pregnant women under the supervision of qualified exercise professionals. We contend that prescreening and the supervisory role of qualified exercise professionals contributed to the low incidence of adverse exercise-related events. The role of the qualified exercise professional might be especially important for previously inactive pregnant women when initiating exercise programs.

Although there was high variability in exercise prescription, the most common exercise prescriptions were exercise intensity of 50% to 70% of maximum, frequency of 3 times per week, exercise sessions of at least 30 minutes per day, and programs lasting between 12 and 24 weeks. Risk of an adverse event was low across trimesters and across a variety of types of exercise (eg, stationary cycling, walking, water-based activities like swimming). Table 1 presents specific recommendations concerning the risk of adverse events during exercise in pregnant women presenting without contraindications. A decision tree for physical activity screening and general risk classification is presented in Figure 1.

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Figure 1

Clinical decision tree for assessing the risk of adverse events during physical activity in pregnant women: This decision tree can be used to categorize a pregnant woman as high or low risk, thereby informing requirements for the prescription of physical activity and the monitoring of exercise programs.

^*Despite being at low risk, pregnant women who were not previously active might wish to consult qualified exercise professionals for advice on preferred activities.