Timing of planned delivery in uncomplicated monochorionic diamniotic twin pregnancies: a review of the literature

Monochorionic diamniotic (MCDA) twins comprise of 20–30% of twin pregnancies; roughly 50% will be undelivered and ‘uncomplicated’ beyond 32 weeks gestation. This review details accumulating data regarding the risk of intrauterine fetal demise (IUFD) in ‘uncomplicated’ MCDA twins and risks associated with prematurity. ‘Uncomplicated’ MCDA twins are at increased risk for IUFD, even when under intensified surveillance in tertiary care centers. The prospective risk of IUFD in uncomplicated MCDA varies among different studies, with reported rates of up to 3.3% at 34 weeks and 2.2% at 36 weeks. If single IUFD occurs, it exposes the surviving co-twin to potential significant morbidity and mortality. It had been suggested that elective preterm delivery would eliminate this risk, but recent evidence of prematurity morbidity are accumulating. With more intensified monitoring from 32 weeks, it is possible that the rate of IUFD is lower than anticipated. We reviewed the data regarding these risks and their contribution to the decision-making process.