Fetal anomalies in twin pregnancies

Abstract

Twinning increases the chances of structural anomaly in the fetus. Discordance in physical development of the fetuses raises both ethical and management dilemma. Chorionicity plays an important role when selective feticide is an option. Anomalies found in singleton pregnancy can also be found in twins. Certain anomalies, such as acardiac fetus, are unique to monochorionic (MC) twin gestations. These anomalies may require in utero intervention to salvage its normal co-twin. Structural abnormalities, such as obstruction in fetal gastrointestinal tract resulting in polyhydramnios, can threaten the loss of the whole pregnancy. In MC twins, demise of the anomalous fetus can result in either demise or cerebral palsy of its co-twin. Fetal cord occlusion of the anomalous fetus can be offered to prevent these deleterious effects to its normal co-twin. Discordance of karyotypes in dichorionic (DC) twins is increasingly diagnosed in prenatal period. Selective feticide in this situation is simpler, but more ethical concerns are being raised. The technical and ethical considerations related to various kinds of discordance fetal malformations in the twin pair will be discussed in this review article.