Over the past 25 years, babies born by in vitro fertilization have increased in birthweight by 200 g, finds a new study. The study is published in the journal Human Reproduction.// The research highlights a possible change between babies born in the earlier years of the technique and today's IVF infants.
‘In recent times, embryos are frozen to remove any potential risks of low birthweight and to foster normal birth weight and early growth.’Existing studies based on children born in the first 20 or 30 years of IVF treatment show that they tend to have a low birthweight, which studies of non-IVF children have shown may carry a possible risk of health problems in later adult life.
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A November 2018 paper from the team led by Professor Daniel Brison showed for the first time that IVF babies also show postnatal catchup growth after low birthweight, which may add to the risk.
Their study showed that freezing embryos seems to offset the risk, resulting in babies with more normal birthweight and early growth.
Most IVF embryos are implanted fresh, though techniques have changed markedly since its earliest days.
However, the latest study from the team shows that as well as increases in the success rate of IVF, birthweights have also increased, by an average of nearly 180g over 25 years - or just under10% - irrespective of which method of IVF is used.
Professor Brison said: "Although it is too soon to know if there will be any long term health impact on earlier IVF children, such effects would in any case be small.
"Our research further suggests that the newest generation of IVF children may be at lower risk.
"We believe that is likely to be because IVF techniques have changed markedly over the past 25 years -though it's hard to pin point exactly which changes might be important."
The current research is a retrospective study of nearly 3000 singleton live births at St Mary's Hospital Manchester.
The November paper is a national register-based study linking the HFEA register of all IVF children to maternity databases in Scotland with records of birthweight and early child growth for 5000 IVF children.
Both studies were funded by EU science grants.