Twin-to-twin transfusion syndrome: polyhydramnios-associated changes in maternal plasma volume and maternal plasma aldosterone concentrations. A preliminary study.

OBJECTIVE

Our aim was to evaluate the consequences of polyhydramnios on maternal plasma volume and maternal serum aldosterone and atrial natriuretic peptide (ANP) concentrations in monochorionic twin pregnancies complicated by twin-to-twin transfusion syndrome (TTTS).

METHODS

The maternal plasma volume, ionograms as well as plasma ANP and aldosterone concentrations were compared in normal monochorionic diamniotic twin pregnancies and in TTTS.

RESULTS

The maternal plasma volume was normal in TTTS despite severe polyhydramnios. The plasma aldosterone concentration was higher in pregnancies complicated by TTTS.

CONCLUSION

The high plasma aldosterone concentration is likely to maintain normal plasma volume despite progressive extravascular volume enhancement. This suggests that TTTS is present early in pregnancy as a chronic phenomenon starting before its clinical expression and may trigger compensatory maternal hyperaldosteronism.