Second trimester maternal serum inhibin-A in fetal anemia secondary to hemoglobin Bart's disease.

OBJECTIVE

To compare the levels of inhibin-A between pregnancies with fetal anemia secondary to Hb Bart's disease and pregnancies with normal non-anemic fetuses.

METHODS

Sixty-five pregnancies at risk of fetal Hb Bart's disease scheduled for cordocentesis at 18-22 weeks were prospectively recruited into the study. Inhibin-A levels were measured from maternal blood drawn before cordocentesis. Fetal blood samples were collected for fetal Hb typing and hemoglobin (Hb) levels.

RESULTS

Maternal serum inhibin-A was significantly higher in women with fetal Hb Bart's disease than those with unaffected fetuses (1.03 MoM (multiple of median) and 0.75 MoM, respectively, p = 0.001). The relationship between maternal serum inhibin-A and fetal Hb level was a quadratic equation; inhibin-A = 5.248 - 9.415(Hb) + 4.919(Hb)(2) (r(2) = 0.274, p < 0.001). Maternal serum inhibin-A did not correlate with cardiomegaly but was significantly associated with placental thickness; inhibin-A = 1.372 - 0.751(Pl) + 0.214(Pl)(2) (r(2) = 0.237, p = 0.007).

CONCLUSIONS

Maternal serum inhibin-A levels were significantly higher in pregnancies with fetal Hb Bart's disease. The elevation of inhibin-A was likely to be a consequence of fetal anemia and placentomegaly. Since inhibin-A is commonly used as a component of quadruple test; the calculated risk of Down's syndrome may be unreliable in pregnancies with fetal Hb Bart's disease or possible fetal anemia.