OR16-07 Markers of Primary Aldosteronism in Women with Hypertensive Disorders of Pregnancy

Abstract Disclosure: J. Yang: None. M. Davies-Tuck: None. W. Matthew: None. E. Ng: None. A. Baruah: None. A. Mahajan: None. K. Palmer: None. Background: Hypertensive disorders affect 5-10% of pregnancies and are the leading cause of maternal mortality in developed countries. The most common endocrine cause of hypertension is primary aldosteronism (PA), a condition of excess aldosterone production which is potentially curable. Even accounting for hormone fluctuations during pregnancy, an elevated aldosterone-to-renin ratio (ARR > 70) and/or low renin (< 10 mU/L) suggests PA. While PA affects ∼10% of the general hypertensive population, it is rarely diagnosed in pregnancy, with a reported incidence of 0.11 per 100 000 pregnancies in a national observational study using the UK Obstetric Surveillance System. Low diagnosis rates may stem from insufficient PA screening, despite the opportunity for timely intervention to address this highly modifiable risk factor for hypertension in pregnancy. Aim: To determine the prevalence of possible PA, defined by ARR > 70 pmol/mU and/or renin concentration < 10 mU/L, in a cohort of women with hypertensive disorders of pregnancy; Methods: We conducted a secondary analysis of the Pre-eclampsia and Cardiovascular Health (PREACH, n=73) and Pre-eclampsia Diagnosis in Pregnancy (PreDIP, n=90) studies,. These two cohort studies collected detailed pregnancy and birth outcomes, and plasma samples, from pregnant women with hypertension or pre-eclampsia, or at high risk of pre-eclampsia. Plasma aldosterone concentration was measured using LC-MS/MS, while renin concentration was measured using immunoassay and the aldosterone renin ratio (ARR) was computed. Differences in ARR, and rates of elevated ARR (>70) and low renin (<10), between different trimesters of pregnancy and by the type of hypertensive disorder of pregnancy were determined. Results: Of 163 women (mean age 32.3±5.6 years; BMI 31.7±8.6), 28.8% (n=47) had elevated ARR >70, 21.4% (n=35) had renin concentration < 10 mU/L, while 38% (n=62) had either ARR > 70 and/or renin < 10 mU/L. The proportion with ARR > 70 was comparable across the second and third trimesters (with only two samples from the first trimester), while the proportion with renin <10 was higher in the third trimester (15% in Trimester 2 and 23% in Trimester 3). We also observed differences by hypertension type, with 28% (28/99) in those with preeclampsia, 21% (5/24) in those with both primary hypertension and preeclampsia, 35.5% (12/37) in those with gestational hypertension, and 33% (1/3) in those with primary hypertension having an elevated ARR. Conclusion: This is the first study to systematically examine aldosterone and renin in women with hypertensive disorders of pregnancy. We demonstrated that one in three women had markers suggestive of PA, even accounting for hormonal fluctuations in pregnancy. Data collection is ongoing to evaluate the relationships between PA markers and clinical outcomes, and determine the impact of having a PA phenotype during pregnancy. Presentation: Sunday, July 13, 2025