IVF babies grow up heavier and may have higher risk of obesity – New Scientist

Whats the weight?

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By Jessica Hamzelou

SINCE the first test tube baby arrived 39 years ago, an estimated 6.5 million children have been born thanks to IVF and similar techniques. But we are only just starting to learn about the long-term health of people conceived using assisted reproduction techniques (ART), who may have a higher risk of obesity in later life.

Today, 1 in every 30 babies in Japan is conceived by ART, says Tomoya Hasegawa of Tokyo Medical University. These babies are usually healthy, but tend to have a lower birth weight. Large studies that didnt look at conception method have previously found that low birth weight is linked to adult obesity and diabetes.

To investigate further, Heleen Zandstra of Maastricht Medical Centre, the Netherlands, and her team have been comparing the effects of using two different culture media to support the growth of early IVF embryos. Earlier they had found that one of these was associated with babies that were 112 grams lighter at birth than those beginning life in the other medium. Thats a big difference, considering babies only weigh about 3 kilograms, says Zandstra.

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Now the team have followed up on these babies at the age of 9, recording the height, weight and fat mass of 136 children, as well as blood pressure and heart rate.

They were surprised to find that, while children conceived using each type of culture medium were around the same height, the BMI of the group that had been lighter at birth was an average of 0.9 lower than those who had been heavier babies. There was a difference in weight of 2 kilograms, says Zandstra.

Given that heavier children are more likely to develop obesity later on, the results are worrying

However, both groups were heavier than average 9-year-olds living in similar circumstances, and had more abdominal fat. Given that heavier children are more likely to become obese later in life, the results are worrying, says Zandstra, who presented her findings at the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) in Switzerland in July.

At the same meeting, Hasegawa presented his analysis of 1830 children in Japan. His team found that babies conceived using ART were heavier than naturally conceived babies when they were born, but there was no real difference at 18 months. However, the ART children were heavier again at 6 years old. The results were surprising, says Hasegawa.

What this might mean for adult health in unknown. Louise Brown, the first person born via IVF, is only 39 we dont know yet what will happen to IVF-conceived people in their 50s, says Zandstra.

But people neednt be wary of fertility treatment. We know that IVF is safe, because we have so many children, says Arianna DAngelo, who coordinates the ESHRE group on safety in assisted reproduction. We shouldnt worry, but we should be doing more to monitor children. Studies might flag up problems later in life, says DAngelo.

This article appeared in print under the headline IVF babies grow up to be heavier

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IVF babies grow up heavier and may have higher risk of obesity - New Scientist