Background
International guidelines are increasingly focusing on secondary hypertension (2HTN) screening in young adults with chronic hypertension (CHTN). Reported prevalence of CHTN in young women varies, and there is limited evidence regarding 2HTN in pregnancy or impact on pregnancy outcomes.
Methods
We conducted a cohort study of pregnancies complicated by CHTN at two obstetric centres in Melbourne from 2008-2024. Clinical data collected included maternal demographics and medical conditions, maternal and neonatal birth outcomes, and details of 2HTN screening and diagnosis.
Results
Of 492 pregnancies with CHTN, 40% had undertaken screening for secondary causes. Of those, 21% were diagnosed with 2HTN. Secondary screening mostly constituted renal evaluation (imaging, serum creatinine, urine studies), renal artery Doppler, and endocrine evaluation (aldosterone:renin ratio). Most screening occurred before conception. The commonest causes of 2HTN were chronic kidney disease (83%, most commonly ADPKD, IgA nephropathy or reflux nephropathy), followed by fibromuscular dysplasia (7%) and primary hyperaldosteronism (5%). Multivariate logistic regression identified no significant clinical predictors of 2HTN. Importantly, women with 2HTN had no statistically significant increase in rates of preeclampsia, pre-term birth or small for gestational age neonates compared to those with primary CHTN.
Conclusion
This study provides insight into the frequency and aetiology of secondary hypertension in pregnancy. While no clear clinical predictors of 2HTN were identified, the predominance of renal causes supports routine renal assessment in women with chronic hypertension. Reassuringly, analysis of outcomes in the cohort of 2HTN does not show excess risk above that of women with primary chronic hypertension.