Direct and transplacental intrauterine fetal therapy

Several approaches for an intrauterine fetal therapy have been reported in recent years for different congenital diseases. This article concentrates especially on the treatment of the congenital adrenal hyperplasia and other rare enzymatic defects, on abnormal fetal thyroid function and fetal tachyarrhythmia. Results of intrauterine treatment of congenital adrenal hyperplasia are optimal, when maternal dexamethason therapy is started very early in pregnancy, preferable at 6 weeks of gestation. Other rare congenital defects are methylmalonic acidemia, a functional vitamin B-12 deficiency, and biotin-responsive multiple carboxylase deficiency. Transplacentar treatment was reported by administration of cyanocobalamin and biotin, respectively. Sonographic prenatal diagnosis of a goiter in fetuses with intrauterine hypothyreosis has been described previously. Treatment by injection of thyroxine into the amniotic fluid was successful and size of the fetal thyroid decreased. Fetuses are at risk of hyperthyreosis, if maternal thyroid stimulating antibodies cross the placenta. Presenting symptoms might be fetal tachycardia, general hydrops or even intrauterine fetal death. Initiation of prenatal therapy with propylthiouracil is recommended in these cases. Successful intrauterine therapy of fetal tachyarrhythmia has been reported using digoxin alone or in combination with flecainide. In most cases fetal hydrops resolved and therapy via cordocentesis was not necessary. However in fetuses with complete AV-block and general hydrops there is no standardised protocol for the intrauterine treatment in the literature.