Multiple pregnancy complicated by higher risks of spontaneous abortion, fetal growth retardation and congenital anomalies than single births associated a result of crowding and impaired circulation.
After in-vitro fertilization up to one-third of women have multiple gestations.
Increase perinatal morbidity and mortality that can be reduced by multifetal pregnancy reduction.
Reductions from triplets to twins and from quadruplets to twins carry outcomes as good as those of unreduced twin gestations.
Multiple gestation occur in 1.1% of pregnancies after natural conception.