Editing In vitro fertilisation (section)

===Multiple births===
The major complication of IVF is the risk of [[multiple birth]]s. This is directly related to the practice of transferring multiple embryos at embryo transfer. Multiple births are related to increased risk of pregnancy loss, [[obstetrical complications]], [[preterm birth|prematurity]], and neonatal morbidity with the potential for long term damage. Strict limits on the number of embryos that may be transferred have been enacted in some countries (e.g. Britain, Belgium) to reduce the risk of high-order multiples (triplets or more), but are not universally followed or accepted. Spontaneous splitting of embryos in the uterus after transfer can occur, but this is rare and would lead to identical twins. A double blind, randomised study followed IVF pregnancies that resulted in 73 infants, and reported that 8.7% of singleton infants and 54.2% of twins had a birth weight of less than {{convert|2500|g|lb}}.<ref>{{cite journal |vauthors=Olivennes F, Mannaerts B, Struijs M, Bonduelle M, Devroey P |date=August 2001 |title=Perinatal outcome of pregnancy after GnRH antagonist (ganirelix) treatment during ovarian stimulation for conventional IVF or ICSI: a preliminary report |journal=Human Reproduction |volume=16 |issue=8 |pages=1588–1591 |doi=10.1093/humrep/16.8.1588 |pmid=11473947 |doi-access=free}}</ref> There is some evidence that making a double embryo transfer during one cycle achieves a higher live birth rate than a single embryo transfer; but making two single embryo transfers in two cycles has the same live birth rate and would avoid multiple pregnancies.<ref>{{cite journal |vauthors=Kamath MS, Mascarenhas M, Kirubakaran R, Bhattacharya S |date=August 2020 |title=Number of embryos for transfer following in vitro fertilisation or intra-cytoplasmic sperm injection |journal=The Cochrane Database of Systematic Reviews |publisher=Cochrane Database Syst Rev. |publication-date=21 August 2020 |volume=2020 |issue=8 |pages=CD003416 |doi=10.1002/14651858.CD003416.pub5 |pmc=8094586 |pmid=32827168}}</ref>