How and why are triplets disadvantaged compared to twins?

The current epidemic of triplets, a result of the widespread use of assisted reproduction, started less than two decades ago. Its full impact has been appreciated only recently. Triplets are disadvantaged from every perinatal perspective compared to twins--preterm birth, low birth weight, morbidity and mortality--because the human uterus probably is better equipped to carry twins than triplets. Although modern neonatal care has improved survival rates of preterm as well as low-birth-weight triplets, other complications remain and are of great clinical importance. The alternative to carrying triplets--multifetal pregnancy reduction--is associated with improved outcomes, as expected from comparing twin to higher-order multiples. However, the improved outcomes of triplets in recent years might call for second thoughts about the frequent recommendation of multifetal pregnancy reduction of triplets to twins.