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IVF twins face greater risk of neonatal complications
Published on 02/22/10New research has found that dizygotic (non-identical) twins conceived through IVF face an increased risk of neonatal complications, as compared to spontaneously conceived (non-IVF) dizygotic twins.
One of the most recognized complications of IVF is the increased risk of multiple pregnancy. Twins in general run higher risks for complications and death than singletons in the neonatal period. Research has also shown that singleton births after IVF face an increased risk of neonatal complications.2
Evidence has been unclear, however, as to whether IVF twins face an increased risk of neonatal complications as compared to non-IVF twins. Considerable debate has surrounded the question of whether the risks associated with twinning after IVF differ from those caused by twinning itself. Some studies have reported a higher birth weight among IVF twins than spontaneously conceived twins, while most studies have shown no difference in perinatal outcome. A problem in many early studies is that twin outcome after IVF was compared with all spontaneously conceived (non-IVF) twins.3 Most IVF twins are dizygotic (non-identical) but a substantial proportion of spontaneously conceived twins are monozygotic (identical twins, derived from one egg that splits during development rather than from two separate eggs). Monozygosity carries a larger risk for the infant than dizygosity, because the splitting can disrupt development.4
This study therefore sought to compare neonatal outcome among dizygotic twins conceived after IVF with that of non-IVF dizygotic twins conceived spontaneously. The study was limited to different-sex twins who can only originate from two eggs (all identical twins must, by definition, be of the same sex). The study reviewed all births in Sweden from 1982-2007, using nation-wide health registers. The authors identified 1545 pairs of different-sex twins born after IVF, and 8675 pairs of different-sex twins where IVF was not known to have occurred.
The findings indicate that the risk for preterm delivery before 32 weeks was significantly increased among dizygotic twin pairs born after IVF, compared with non-IVF dizygotic twin pairs. There was also an increased occurrence of IVF twin pairs with respiratory problems or jaundice, but only jaundice occurred in a statistically significant excess.
The authors explain that 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.
Lead author, Professor Bengt Källén, from the Tornblad Institute in Sweden, said “The study shows that unlike-sexed (therefore dizygotic) twins born after in vitro fertilization have a worse neonatal outcome than such twins spontaneously conceived. Such a difference is well known for singletons but previous studies have not found it for twins with the exception of one recent Australian study.
“The finding supports the need for a reduction in twinning risk after in vitro fertilization. This can be achieved by single embryo transfer.”
Professor Philip Steer, BJOG editor-in-chief, said “This study suggests that IVF twins, in addition to the risks of twinning itself, may also experience increased neonatal risks associated with IVF. As with IVF singleton births, this difference in risk is likely related at least in part to maternal characteristics and to the fertility problems which led to the need for IVF in the first place.
“Multiple pregnancy remains the single biggest risk of fertility treatment. Twins face an increased risk of preterm birth, low birthweight, and serious health problems. When possible, couples undergoing IVF should be encouraged to opt for single embryo transfer in order to reduce the risk of multiple pregnancy.”
