Some observational studies suggest that maintaining an active lifestyle or adding physical activity to the normal daily schedule of the pregnant woman may attenuate GWG. Clapp and Little (1995) compared exercising women who became pregnant and who continued to exercise at least three times per week to a group of women who stopped exercising once they became pregnant. The rate of GWG and of subcutaneous fat accretion (determined by skinfold thickness) was similar between the two groups during the first and second trimesters but the exercising women gained significantly less body weight and skinfold thickness during the third trimester. On average, the pregnant women who continued to exercise gained about 3 kg less. These observations were from a Norwegian study of 467 pregnant women who answered a questionnaire on physical activity level in week 36 of their pregnancy (Haakstad et al., 2007). Women who exercised regularly had significantly lower weight gain than inactive women in the third trimester only.

In a study of 96 obese women with GDM self-enrolled in either a diet (n = 57) or an exercise plus diet (n = 39) program during the last 2 months of pregnancy, the mean weight gain per week was less in the exercise plus diet group (0.1 ± 0.4 kg versus 0.3 ± 0.4 kg) (Artal et al., 2007). The exercise session consisted of walking on the treadmill or cycling in a semi-recumbent position once a week followed by unsupervised exercise at home for the remaining 6 days. The exercise plus diet group exercised for 153 ± 91 minutes per week. Complications, infant birth weight, and the proportion of cesarean deliveries were comparable between the two groups.

Based on the limited available evidence, the Physical Activity Guidelines Advisory Committee concluded that “unless there are medical reasons to the contrary, a pregnant woman can begin or continue a regular physical activity program throughout gestation, adjusting the frequency, intensity, and time as her condition warrants” (HHS, 2008). The committee added that “in the absence of data, it is reasonable for women during pregnancy and the postpartum period to follow the moderate-intensity recommendations set for adults unless specific medical concerns warrant a reduction in activity.” It is commonly recognized, however, that adequately powered, randomized, controlled intervention studies on the potential benefits and risks of regular physical activity at various dose levels in pregnant women are needed.

Physical activity, such as work, spontaneous activity, fidgeting, and personal chores as well as exercise account for a widely variable fraction of TEE. In some, this may reach only about 15 percent of daily energy expenditure while in others it may be as high as 50 percent (Hill et al., 2004). Most recently, Lof et al. (2008) assessed the effects of maternal physical