Screening for primary aldosteronism in pregnancy

Primary aldosteronism, the most common secondary cause of hypertension is likely to be significantly underdiagnosed in pregnancy and is associated with high rates of adverse maternal and fetal outcomes. Normal pregnancy is associated with a rise in aldosterone and renin levels early in pregnancy making the aldosterone: renin ratio which is normally used to screen for primary aldosteronism, difficult to interpret. Additionally, many laboratories have moved from performing plasma renin activity to measurements of direct renin. Aldosterone, direct renin and aldosterone: renin ratios were determined in 9 women with primary aldosteronism and compared to levels in 33 women with chronic hypertension. All women with primary aldosteronism had a direct renin levels of less than 20 mU/L together with aldosterone:renin ratio of greater than 40. Values for direct renin were significantly lower, and the aldosterone:renin ratio was significantly higher in pregnancy in women with primary aldosteronism compared to women with chronic hypertension. Pregnant women with chronic hypertension who have a direct renin level less than 20 mU/L and aldosterone:renin ratio of greater than 40 should have close surveillance for maternal and fetal complications, and follow-up postpartum should be ensured for definitive testing.