Body mass index and hypertensive disorders of pregnancy

We compared the incidence of the hypertensive disorders of pregnancy in obese women with women of a normal body mass index (BMI).

Prospective observational study in which BMI was calculated accurately early in pregnancy. Women were enrolled after a sonographic confirmation of an ongoing pregnancy. To reduce confounding variables the study was confined to white European women with a singleton pregnancy.

Incidence of pre-eclampsia and gestational hypertension.

In 2230 women, 16.8% were obese. Pre-eclampsia was diagnosed in 3.3% (n=74) and gestational hypertension in 3.0% (n=67). Both pre-eclampsia (p=0.01) and gestational hypertension (p<0.01) were common in obese women compared with normal weight women. Overall 13.1% of obese women developed a hypertensive disorder during pregnancy. When analysed by parity pre-eclampsia occurred in 2.1% of primigravidas and 0.3% of multigravidas. Pre-eclampsia was increased in obese multigravidas (p=0.001), but not obese primigravidas, suggesting that parity is more influential than obesity in the development of pre-eclampsia.

Obese multigravidas are more likely to develop hypertensive disorders in pregnancy and obese primigravidas are more likely to develop gestational hypertension. This is important in clinical practice because maternal weight, unlike parity, is potentially modifiable before or during pregnancy.