Perinatal outcome of singletons and twins after assisted conception: a systematic review of controlled studies

To compare the perinatal outcome of singleton and twin pregnancies between natural and assisted conceptions.

Systematic review of controlled studies published 1985-2002. STUDIES REVIEWED: 25 studies were included of which 17 had matched and 8 had non-matched controls. MAIN OUTCOME MEASURES: Very preterm birth, preterm birth, very low birth weight, low birth weight, small for gestational age, caesarean section, admission to neonatal intensive care unit, and perinatal mortality.

For singletons, studies with matched controls indicated a relative risk of 3.27 (95% confidence interval 2.03 to 5.28) for very preterm (