Interpregnancy body mass index change and risk of hypertensive disorders in pregnancy

Hypertensive disorders are a common cause of maternal mortality. Whether interpregnancy BMI (body mass index kg/m²) gain is associated with hypertensive disorders in a subsequent pregnancy is not unclear.

To examine the association between interpregnancy BMI and hypertensive disorders in women without a history of hypertensive disorders in pregnancy.

This was a retrospective cohort study of all women who had more than one singleton pregnancy at 23 weeks' gestation or greater at a single academic institution. Only the second pregnancy in the dataset was analyzed. We excluded women who had any hypertensive disorder in the index pregnancy. Interpregnancy BMI change was calculated by the change of early pregnancy BMI (within 14 weeks' gestation) measured in the office between the index pregnancy compared to that of the subsequent pregnancy. Women were categorized according to interpregnancy BMI change (BMI loss greater than 2 kg/m², BMI change ±2 kg/m², and BMI gain greater than 2 kg/m²). The primary outcome was any hypertensive disorder (chronic hypertension and pregnancy-associated hypertension). Multivariable logistic regression was performed to calculate adjusted odds ratios (aOR) with 95% confidence interval (95%CI) after adjusting for predefined covariates.

Of 3068 women who were analyzed, 342 (11%), 1698 (55%), and 1028 (34%) had interpregnancy BMI loss greater than 2 kg/m², interpregnancy BMI change ±2 kg/m², and interpregnancy BMI gain greater than 2 kg/m², respectively. Interpregnancy BMI gain greater than 2 kg/m² compared to interpregnancy BMI loss more than 2 kg/m² was associated with increased odds of hypertensive disorders (8.3% vs. 4.0%; adjusted odds ratio 2.20 [95% confidence interval 1.55-3.13]) and pregnancy-associated hypertension (adjusted odds ratio 2.25 [95% confidence interval 1.54-3.27]). Interpregnancy BMI loss greater than 2 kg/m² compared to interpregnancy BMI change ±2 kg/m² was not associated with increased odds of any hypertensive disorders (5.3% vs. 4.0%; adjusted odds ratio 0.58 [95% confidence interval 0.32-1.05]).

Compared to interpregnancy BMI change ±2 kg/m², interpregnancy BMI gain greater than 2 kg/m² was associated with increased odds of any hypertensive disorder. Weight control after pregnancy could be a potentially modifiable factor that may reduce the risk of hypertensive disorders.