ObjectiveTo assess whether waist circumference at the first antenatal visit predicts risk of developing hypertension later in pregnancy.MethodsPregnant women with singleton pregnancies (n= 1142, median age 29 years, interquartile range 25–32 years, 387 primigravidas) were recruited at their first antenatal visits. Using standardized methods, midwives determined the weights, heights (for calculation of body mass index [BMI]), and waist circumferences of all women. Eighty-two women developed pregnancy-induced hypertension, and 21 developed preeclampsia (hypertension with proteinuria).ResultsThe median waist circumference between 6 and 16 weeks' gestation was 79 cm (interquartile range 72–84 cm), and there was no significant relationship between waist circumference and gestational age. Greater waist circumference was noted in subjects who subsequently developed pregnancy-induced hypertension (median 81 versus 77 cm, Mann-WhitneyUtest,P= .002) or preeclampsia (median 80 versus 77 cm,P= .02). The conventional, nonpregnant waist circumference action level of 80 cm gave a Mantel-Haenszel odds ratio (OR) for pregnancy-induced hypertension of 1.8 (95% confidence interval [CI] 1.1, 2.9) and for preeclampsia of 2.7 (95% CI 1.1, 6.8), compared with waists of less than 80 cm. Body mass index values were higher in women who developed pregnancy-induced hypertension (median 26 versus 24,P= .001) or preeclampsia (median 26 versus 24,P= .02). The conventional action limit for a BMI of 25 had an OR for pregnancy-induced hypertension of 2.0 (95% CI 1.2, 3.4) and for preeclampsia of 1.9 (95% CI 0.7, 4.8). Results were similar when the analysis was restricted to data from primigravidas.ConclusionWe conclude that waist circumference up to 16 weeks' gestation can predict pregnancy-induced hypertension and preeclampsia. Therefore, waist circumference could form the basis for health promotion involving raising awareness of the importance of or urging weight reduction for women planning pregnancies.