Influence of pre-pregnancy BMI and gestational weight gain on hypertensive disorders during pregnancy

Background: The past two decades have seen an increase in maternal weight, a known risk factor for hypertensive disorders during pregnancy. However, the inter-relationship between pre-pregnancy BMI, gestational weight gain and hypertensive disorders is not well understood. This study examines the association between pre-pregnancy BMI and hypertensive disorders of pregnancy, stratified by gestational weight gain as outlined by the 2009 Institute of Medicine guideline.

Methods: The Pregnancy Risk Assessment Monitoring System (PRAMS), a nationally representative sample of women who delivered live births in the U.S., was analyzed. Maternal pre-pregnancy BMI was categorized as underweight (< 18.5), normal weight (18.5-24.9), overweight (25-29.9) and obese (≥30). Women were classified as having hypertensive disorders of pregnancy if they reported high blood pressure, pregnancy induced hypertension, preeclampsia, or toxemia during their most recent pregnancy. Pre-pregnancy BMI was stratified by maternal weight gain and ORs and 95% CIs were calculated using logistic regression.

Results: Within each stratum of gestational weight gain, women who were overweight or obese had increased odds of developing hypertensive disorders compared to normal BMI women. The estimates became more robust with increased gestational weight gain. Compared to women with normal pre-pregnancy BMI, underweight women had reduced odds of hypertensive disorders.

Conclusion: Exceeding the recommended guidelines for gestational weight gain may put mothers at risk for a range of hypertensive disorders during their pregnancy. These findings may help encourage obstetricians to effectively consult with patients about maintaining healthy weight gain during pregnancy to improve pregnancy outcomes.