Brain natriuretic peptide and endothelin-1 in the pathogenesis of polyhydramnios-oligohydramnios in monochorionic twins.

OBJECTIVE

We investigated the association between amniotic fluid levels of human brain natriuretic peptide, endothelin-1, and abnormal amniotic fluid volume in monochorionic twins with and without chronic twin-twin transfusion syndrome.

STUDY

DESIGN

Amniotic fluid and fetal blood samples were obtained in utero or at cesarean delivery from monochorionic twins with (n = 20) or without chronic twin-twin transfusion syndrome (n = 10). Concentrations of atrial natriuretic peptide, human brain natriuretic peptide, and endothelin-1 (in picograms per milliliters) were determined by radioimmunoassay.

RESULTS

The amniotic fluid concentrations of human brain natriuretic peptide (P <.001) and endothelin-1 (P <.001) in the recipient fetuses were higher than the donor twins but were similar in the twins with no twin-twin transfusion syndrome. In the donor twins, amniotic fluid concentrations of human brain natriuretic peptide (P <.001) and endothelin-1 (P <.001) were lower than the twin pairs with no twin-twin transfusion syndrome. In both chronic twin-twin transfusion syndrome fetuses (P <.01) and fetuses with no twin-twin transfusion syndrome (P <.001), the amniotic fluid concentrations of human brain natriuretic peptide were high, although the concentrations of the endothelin-1 were lower than the fetal plasma concentrations. A positive association was present between amniotic fluid levels of human brain natriuretic peptide and endothelin-1 (R (2) = 0.51, P <.001, n = 60). Amniotic fluid human brain natriuretic peptide (r = 0.67, P <.001) and endothelin-1 (r = 0.57, P <.01) levels of the recipient twins correlated with the amniotic fluid index.

CONCLUSION

These data suggest that amniotic fluid concentrations of human brain natriuretic peptide and endothelin-1 were highest in the twins with polyhydramnios and lowest in the twins with oligohydramnios, which suggests the importance of these hormones in the regulation of amniotic fluid volume.