A scientist has claimed that some children who are conceived using fertility treatments may have genetic health risks.
Carmen Sapienza, a geneticist at Temple University School of Medicine, has found that a particular type of chromosome modification, known as DNA methylation, is different in a small percentage of children conceived with technological assistance.
The scientist said: ""We found that five to ten percent of these chromosome modifications were different in children born through assisted reproduction and this altered the expression of nearby genes."
However, he added: "We have not yet distinguished whether this is caused by assisted reproductive technologies or other factors such as the couple's infertility."
Problems such as obesity, hypertension and type two diabetes are associated with genetic problems.
The world's first 'test-tube baby' - Louise Brown - has recently given birth to a child of her own who was conceived naturally.
Ms Brown was born in 1978 and is one of some three million people world-wide who were conceived with assisted reproductive technology.