Plasma aldosterone concentration and plasma renin activity decrease during the third trimester in women with twin pregnancies.

OBJECTIVE Changes in the plasma aldosterone concentration (PAC) and the plasma renin activity (PRA) have not been extensively studied in women with twin pregnancies. METHODS The PAC and PRA levels were determined during the second and third trimesters and on postpartum day 3 in 14 normotensive women with twin pregnancies and 80 normotensive and 7 preeclamptic women with singleton pregnancies. RESULTS In women with twin pregnancies, elevated PAC and PRA levels (598 ± 248 pg/mL and 10.0 ± 4.7 ng/mL/h, respectively) in the second trimester decreased significantly during the third trimester (to 396 ± 210 pg/mL and 3.5 ± 2.9 ng/mL/h, respectively), whereas the corresponding PAC increased significantly (from 421 ± 207 to 667 ± 371 pg/mL) and the PRA did not change significantly (from 7.3 ± 3.4 to 6.9 ± 4.2 ng/mL/h) in women with normal singleton pregnancies. These changes in the PAC and PRA levels in women with twin pregnancies resembled those in hypertensive women with singleton pregnancies. CONCLUSIONS In women with twin pregnancies, both the PAC and PRA levels were significantly enhanced during the second trimester, whereas those in the third trimester were significantly reduced compared with those in women with normal singleton pregnancies.