Prenatal Diagnosis of Conjoined Fetuses.

Conjoined twins have an estimated prevalence between one in 50,000 and one in 1,00,000 births. Prenatal two- and threedimensional (2D and 3D) real-time ultrasonography is the most reliable method for establishing a prenatal diagnosis and detecting associated anomalies. Recent improvements in ultrasonography have made early diagnosis of conjoined fetuses in the first trimester possible. Most cases of conjoined twins occur in monochorionic monoamniotic pregnancies, making sonographic identification of distinct placentae and/or intervening amniotic membrane(s) a criterion to exclude fetal conjunction. There are two opposing pathogenetic theories, supporting fission vs fusion of embryos in the early first trimester. In very rare cases of diamniotic monochorionic conjoined twins, a distinct pathogenetic mechanism of conjoined twinning, similar to that of body stalk anomaly may exist. Prenatal diagnosis of conjoined fetuses is essential for further management. Parents need detailed counseling in order to decide among various management options--(1) pregnancy continuation and scheduled neonatal surgery, (2) termination of pregnancy, and (3) multifetal pregnancy reduction or selective fetocide in cases of high-order multifetal pregnancies with a component of conjoined fetuses. Pre- and postnatal management is challenging, and an interdisciplinary medical team involving obstetricians, neonatologists, pediatric surgeons, and anesthetists should carefully approach and assist parents in their decisions. In special cases, additional consultation by specialized centers in other countries may be needed. Furthermore, adequate psychosocial support should be offered, and palliative care services should be available in selected cases. [ABSTRACT FROM AUTHOR]