IVF babies more likely to grow up overweight, scientists warn

From Victoria Allen Science Correspondent in Geneva

CHILDREN born through IVF are more likely to be overweight, a study found.

Experts revealed ‘test tube babies’ have their genes altered, with those born through fertility treatment weighing 1½lb more on average by the age of nine.

Starting out in a laboratory dish instead of their mother’s body may cause children to store up more fat – meaning they could become heavier even when they eat as much as their naturally conceived peers.

Lead researcher Dr Heleen Zandstra, from Maastricht University in the Netherlands, said: ‘This is enough of a weight difference to be concerning, because overweight children are more likely to become overweight adults. We think IVF children may be predisposed to cardiovascular problems, including heart problems, in later life. They may be programmed wrongly by IVF to store food as fat throughout their lives.’

The study, presented at the European Society of Human Reproduction and Embryology conference in Geneva, looked at 136 children born through IVF in the Netherlands. Those of average height, aged nine-and-a half, weighed 1½lb more than children of the same age and height – a difference of 2.1 per cent.

The hormones given to women to harvest their eggs for IVF could cause their children to be overweight, by changing the way their cells behave in the first days of life.

IVF babies begin as an embryo growing in a laboratory dish, with the Dutch team discovering the different chemicals used may change the birth weight of children.

While this chemical soup is thought to make IVF children slightly smaller at birth, it could then lead to weight gain when they are older. Explaining the phenomenon, Dr Zandstra said: ‘Research has suggested these chemicals cause IVF babies to be born smaller. They might change the way the baby absorbs nutrients, or how the placenta passes them on.

‘At an older age this may cause a child born smaller to store more food as fat, because their body wants to make sure they get enough.’

Evidence is growing IVF children may be bigger. Japanese research presented at the conference also found they were taller at the age of six than those conceived naturally.