This study was designed to test the hypothesis that continuing a regular regimen of recreational endurance exercise alters the time-specific rate of maternal weight gain and subcutaneous fat deposition during pregnancy. Serial measurements of body mass and 5-site skinfold thickness were obtained from 44 women before and during pregnancy who continued their preconceptional exercise regimen throughout pregnancy and from women who voluntarily stopped their preconceptional exercise regimen either before conception (N = 31) or reduced it below baseline fitness levels in very early pregnancy (N = 4). In the first and second trimester, the rate of weight gain and change in skinfold thicknesses were unrelated to exercise performance. However, those who continued exercise had a reduced rate of weight gain and change in skinfold thickness at specific sites in the last trimester of pregnancy. Overall weight gains were (mean +/- SEM) 13.0 +/- 0.5 kg and 16.3 +/- 0.7 kg in the exercise and control groups, respectively, and the increases in the sum of skinfolds were 22 +/- 2 mm and 31 +/- 2 mm, respectively. We conclude that continuing a regular exercise regimen throughout pregnancy does not influence the rate of early pregnancy weight gain or subcutaneous fat deposition but decreases both in late pregnancy. However, overall pregnancy weight gain remains well within the normal range.