Provoking factors for postpartum chronic hypertension in women with preceding gestational hypertension/preeclampsia: A longitudinal cohort study of 22,798 pregnancies

Background: A proportion of women with pregnancies complicated by gestational hypertension/preeclampsia (GH-PE) will have persistent postpartum chronic hypertension (CHTN). Common risk factors for postpartum CHTN include older age, pre-existing CHTN, smoking, pre-pregnancy obesity (elevated BMI), and co-morbidities such as thyroid disorders. However, most of explored risk factors are pre-pregnancy factors, and were mainly based on studies with small sample size. Methods: To investigate provoking pre-pregnancy and intra-pregnancy factors for postpartum CHTN in women with preceding GH-PE, the cohort study enrolled 22,798 index pregnancies to analyze individual characteristics, co-morbidities and postpartum outcomes after excluding women with pre-existing CHTN. Results: Among 2,132 GH-PE pregnancies, 428 (20.1%) were complicated with postpartum CHTN. After adjustment, logistic regression analysis revealed excessive pregnant weight gain (≥10 kgw at 28 weeks' gestation) (OR: 14.50, 95% CI: 11.02-19.08) and gestational diabetes mellitus (GDM) (OR: 6.25, 95% CI: 4.98-7.85) were major risk factors for developing CHTN, other than age (OR: 1.80, 95% CI: 1.68-1.93), pre-pregnancy BMI (OR: 3.15, 95% CI: 2.75-3.60), severity of GH-PE (OR: 2.46, 95% CI: 1.97-3.07), smoking (OR: 1.79, 95% CI: 1.35-2.38), and overt DM (OR: 2.30, 95% CI: 1.73-3.06). Conclusion: Excessive pregnant weight gain and GDM are major intra-pregnancy risk factors for postpartum CHTN in women with preceding GH-PE. Future studies should investigate interventions such as a healthy diet, appropriate physical exercise and avoidance of excessive pregnant weight gain as a means to reduce the frequency of CHTN following pregnancy.