Challenges in the management of twin pregnancy discordant for abnormality

Abstract

Prenatal diagnosis in the setting of a twin pregnancy is challenging. The frequency of abnormalities is higher in twin than in singleton pregnancies, particularly in monozygotic pregnancies. The finding of an abnormality in one twin with a normal co-twin occurs in about 85% of cases of abnormality and raises difficult management decisions. Determination of chorionicity is pivotal in further management as vascular anastamoses in monochorionic pregnancies influence the outcome as well as the interventions which are possible. Options include expectant management of the pregnancy or selective fetocide. The latter carries risks to the pregnancy of miscarriage and preterm labour. These risks are higher in monochorionic than dichorionic pregnancies. In addition death of one twin of a monochorionic pair can result in death or organ damage in the co-twin. The method of selective fetocide also differs depending on chorionicity. In dichorionic twins, intracardiac injection of KCl is the method of choice, while in monochorionic pregnancies, cord occlusion by either laser coagulation or bipolar coagulation is used. Extensive counselling of parents is necessary prior to prenatal diagnosis, and especially prior to any intervention.

Keywords: Twins; Fetal abnormality; Discordant