Progression of gestational hypertension to pre-eclampsia: A cohort study of 20,103 pregnancies

Objective: To investigate previously un-identified risk factors for the progression of gestational hypertension (GH) to pre-eclampsia (PE) by considering Grade III preterm placental calcification (PPC) and excessive weight gain (≧10kgw) at 28weeks gestation.

Methods: At a tertiary teaching hospital, obstetric ultrasonography was performed at 28weeks gestation to establish a diagnosis of grade III PPC. Weight gain during pregnancy was recorded at the same time. Pregnancies complicated with chronic hypertension, major fetal congenital anomalies, termination before 24weeks gestation, and abortion before 20 weeks gestation were excluded.

Results: In the current cohort study, 20,103 pregnancies were enrolled and categorized as normal blood pressure (NBP; n=18,223) and GH-PE (n=1880) groups. According to severity of the diseases, the GH-PE group was further divided into GH (n=1088), PE (n=792), and severe PE (n=209) groups. There were significant differences between the NBP and GH-PE groups in known factors, including maternal age, BMI, parity, multi-fetal pregnancy, and co-morbidities (all p<0.001), all of which increased the risk for GH-PE. Regarding the progression of GH to PE and severe PE, there was a much greater frequency of excessive weight gain (51.2% and 49.0% vs. 9.3%) or PPC (63.2% and 61.6% vs. 12.1%) in the severe PE and PE groups than the GH group. Logistic regression analysis revealed that PPC was a significant and independent risk factor for progression of GH to PE (OR, 13.71; 95% CI, 10.25-18.33) and severe PE (OR, 12.42; 95% CI, 8.89-17.35), as well as excessive weight gain during pregnancy (OR, 8.92; 95% CI, 6.67-11.92 and OR, 10.25; 95% CI, 7.30-12.40).

Conclusion: Being a pathologic implication, the presence of PPC or excessive weight gain during pregnancy may precede progression of GH, and can serve as a warning or marker that requires closer surveillance for maternal and fetal well-being. Based on the findings of PPC and excessive weight gain, at-risk pregnant woman should be counseled to facilitate early intervention or referral. In addition, avoiding excessive weight gain during pregnancy may reduce the risk of GH progression to PE.