The relations of exercise, employment, and other daily activities during pregnancy with pregnancy outcomes were examined using data from the Missouri Maternal and Infant Health Survey. Maternal surveys were available for the following singleton birth categories: 450 fetal deaths; 782 very low birth weight (VLBW, < 1,500 g); 802 moderately low birth weight (MLBW, 1,500-2,499 g); and 794 normal birth weight (NBW, > or = 2,500 g). All mothers were Missouri residents at the time of their December 1989 to March 1991 deliveries. It was found that VLBW mothers had exercised during pregnancy significantly less than NBW mothers. When compared with NBW mothers before pregnancy, VLBW mothers had been just as likely not to exercise as NBW mothers (odds ratio (OR) = 0.88, 95% confidence interval (CI) 0.69-1.12). During the first, second, and third trimesters, the odds ratios decreased to 0.70 (95% CI 0.53-0.92), 0.54 (95% CI 0.40-0.74), and 0.33 (95% CI 0.20-0.53), respectively. The VLBW mothers also were less likely to exercise during the third trimester than MLBW mothers (OR = 0.34, 95% CI 0.21-0.54) or mothers with fetal deaths (OR = 0.36, 95% CI 0.19-0.67). During the 3 months after pregnancy, none of the exercise odds ratios were statistically significant between groups. No significantly increased risks were found between employment during pregnancy or other daily activities and adverse pregnancy outcome. The study supports the recently relaxed guidelines of exercise during pregnancy.