(1030) Outcomes of Non-Participants in a Chronic Hypertension in Pregnancy Treatment Trial: CHAP Ancillary Observational Study

Objective: In CHAP, treatment of pregnant women with mild chronic (C) HTN to a BP goal < 140/90 mmHg (vs. no treatment unless BP ≥160/105) was beneficial and safe. Since only 1:12 screened women participated in the trial, we implemented an ancillary study to compare characteristics and outcomes of non-participants without severe CHTN to randomized participants.

Study Design: Retrospective observational cohort (OC) study of patients with new or known CHTN who were screened but not randomized in CHAP. We included patients who were excluded due to advanced gestational age (GA), BP not ≥140/90 mmHg off medication or who declined randomization. Those with severe or secondary CHTN, FGR, kidney disease, diabetes class D or greater and/or stillbirth/pregnancy loss remained excluded. Patients were randomly selected per site in a ratio of 1 OC: 2 randomized. Outcomes were ascertained by abstraction of records without adjudication. The primary outcome was a composite of preeclampsia + severe features, perinatal death, indicated preterm birth (PTB) < 35 weeks or abruption. The sample size of 1100-1200 in the OC would provide 80-85% power to estimate a 25-30% difference in the outcome from a reference >30%.

Results: A total of 1102 patients were included in the OC; compared to randomized groups, they were more likely to be NH white, non-diabetic and have private insurance with lower mean systolic and diastolic BP (4-5 mmHg) and mean BMI (2 kg/m²). The primary composite was more frequent in the control but not the active group compared to the OC (Table). Perinatal death, PTB, GA at delivery and preeclampsia were more frequent in both active and control groups.  Additional components of the primary and secondary outcomes were more frequent in the control group (Table). Results were consistent in covariate-adjusted models.

Conclusion: CHAP screened non-participants without severe HTN had a more favorable risk profile than participants and better pregnancy outcomes than active and control CHAP participants even after adjustments.