In a recently published article in Human Reproduction, Swedish researchers have demonstrated that Sweden’s dramatic increase in single embryo transfer (SET) over the last 5 years, to 70% SET, has resulted not only in the expected decrease of multiple births and associated pre-maturity, but also in measurable, better health outcomes for IVF children and their mothers.
For mothers, the increased risk of pre-eclampsia (dangerously high blood pressure) and PROM (premature rupture of membranes) during pregnancy, previously demonstrated after IVF, has now virtually disappeared.
For children, the risk of neonatal death was reduced from 3 times the background risk to nearly nil. Neonatal diagnoses like cerebral bleeding, respiratory problems and sepsis also decreased significantly, as did the risk of cerebral palsy.
During the same time period, efficacy of IVF did not suffer, with success rates remaining just below 30 % of deliveries per embryo transfer with only 5% being twins.
The researchers conclude that a high proportion of SET leads to fewer multiple births and thereby to less pre-maturity and low birth-weights. This consequently leads to a number of better health outcomes for mother and child.
Källén B, Finnström O, Lindam A, Nilsson E, Nygren KG, Otterblad Olausson P Trends in delivery and neonatal outcome after in vitro fertilization in Sweden: data for 25 years. Human Reproduction 2010 Apr, 25 (4) 1026-34
“Sweden has led the way in Europe for reducing the number of embryos for transfer after IVF treatment. Since 2002 the law in Sweden dictates that only one embryo should be transferred, unless the risk of twin was judged to be small. Single embryo transfers rose from around15% in 2001 to close to 70% by 2004. Remarkably during this time the overall live birth rate has remained constant, and one of the highest in Europe! Recent evidence suggests that this policy has paid off in terms of improved outcomes for both mother and baby.
Kallen and colleagues, reporting in Human Reproduction earlier this year, reviewed the obstetric outcome of the 27,386 births in Sweden between 1982 and 2006 after in vitro fertilisation in comparison with all 2,603601 deliveries that occurred during the same time frame.
There was a substantial decline in multiple births, largely due to the impact of single embryo transfer. This led to a significant fall in neonatal illnesses, largely associated with multiple pregnancies, such as preterm births, low birth weight, cerebral haemorrhage, lung disease, and neonatal infections. Mothers have also faired better, with a decline in the number of women with pre-eclampsia, and those who experience premature rupture of membranes, which are increased in multiple pregnancy.
Even taking other factors that affect delivery and neonatal outcome into account, these improvements validate the policy of single embryo transfer to avoid multiple pregnancies. UK clinicians and patients should gain confidence from this study in the quest to reduce the multiple birth rates in the UK.”
Chair, British Fertility Society