Objective: To compare neonatal outcome among twins conceived after in vitro fertilisation (IVF) with that of spontaneously conceived twins.
Design: Comparison of different-sex (dizygotic) twins born after IVF with non-IVF dizygotic twins.
Setting: National health registers in Sweden.
Population: All births in Sweden during the period 1982-2007.
Methods: We studied gestational duration, lowest birthweight and birthweight difference in the twin pair, presence of one or two twins with a respiratory complication, and with jaundice in one or both twins. Risk estimates were calculated as odds ratios with adjustments for year of birth, maternal age, parity and smoking in pregnancy.
Main outcome measures: Gestational duration, birth weight, respiratory complications, jaundice.
Results: We studied 1545 pairs of dizygotic twins born after IVF, and 8675 pairs of dizygotic twins where IVF was not known to have occurred. The risk for preterm delivery before 32 weeks of gestation was significantly increased among dizygotic twin pairs born after IVF compared with non-IVF dizygotic twin pairs. No significant difference in low birthweight or birthweight difference within twin pairs was seen. There was an increased occurrence of twin pairs with respiratory problems or jaundice, but only the latter diagnosis occurred in a statistically significant excess.
Conclusions: The study confirms recent findings that IVF is associated with an increased risk for some neonatal complications, not only among singletons but also among twins.