The high twin birth rates carry a considerable resource implication on both the health care system and perinatal outcome. It has been estimated that the annual cost of caring for multiples born prematurely after ART is in excess of $1 billion annually or$52,000 per infant. Perinatal morbidity and mortality figures among multiples are also sobering. Population-based studies have reported stillbirth and neonatal mortality rates in twins in the order of 18 per 1000 births and 23 per 1000 birth, respectively, compared to 5 per 1000 births in singleton pregnancies (Table 29-1). Survival rates among multiples are also not uniformly distributed, and the effect of chorionicity on survival is profound (Table 29-2...