(770) Antihypertensive therapy and placental vascular insults in pregnant individuals with mild chronic hypertension

Objective: A perceived barrier to utilizing antihypertensive agents to treat gravidae with mild cHTN was a concern for placental underperfusion and fetal growth restriction (FGR). Based on the results of the Chronic Hypertension and Pregnancy (CHAP) Trial, we hypothesized that treatment to achieve a BP < 140/90 during pregnancy would have no effect on the frequency or type of placental vascular insults compared to no treatment.

Study Design: Planned secondary analysis of the CHAP Trial, an open-label, multicenter, RCT where gravidae ≤23 weeks with mild cHTN were randomized to antihypertensive medications with a goal BP of < 140/90 (active group) or deferred  treatment  until BP >160/105 (controls). A subset of participants had placental pathology, inclusive of those from the active group (n=695) and controls (n=698). Histological placental vascular insults included: 1) maternal vascular malperfusion, 2) Infarction, 3) Maternal floor infarction, 4) Decidual arteriopathy, 5) Fibrin depositions, 6) Intervillous hemorrahage; 7) Fetal thrombotic/vascular malperfusion, and 8) Vascular necrosis of fetal plate vessels. The frequency of gross and microscopic placental vascular insults were compared between groups. p< 0.05 was considered significant.

Results: Most participants were enrolled in the first trimester of pregnancy and there were no significant differences at baseline between groups (Table 1). Despite a significantly higher placental weight percentile in the control group (Table 2), there were no significant differences in the proportion of FGR cases (Table 1) nor were there significant differences in the frequency of placental vascular insults (Table 2) between groups.

Conclusion: Among gravidae with mild cHTN, neither the occurrence of FGR nor placental vascular insults differed significantly by treatment group. Thus, maintaining a goal BP of < 140/90 is of fetal benefit with no further risk of vascular compromise of the placenta. This suggests that changes in the frequency of placental vascular insults are unlikely to be a mechanism by which goal BP < 140/90 treatment of mild cHTN improves pregnancy outcomes.