More than three million children have been born as a result of assisted reproductive technologies（辅助生育技术） since the birth of the first "test tube baby" in 1978. While the majority of these children are healthy and normal, as a group they are at greater risk of certain kinds of birth defects（先天缺陷） and being low birth weight, which is associated with obesity¹, hypertension and type 2 diabetes²（糖尿病） later in life. Carmen Sapienza, a geneticist at Temple University School of Medicine, studies the impact of the environment on genes⁴ by comparing one type of chromosome⁵（染色体） modification⁶, called "DNA⁷ methylation（甲基化） " between children conceived in the traditional fashion with children born as a result of assisted reproduction.

"We found that 5-10 percent of these chromosome modifications⁸ were different in children born through assisted reproduction, and this altered the expression of nearby genes," he said. "But we have not yet distinguished⁹ whether this is caused by assisted reproductive technologies or other factors such as the couple's infertility¹⁰."

Because some of the affected¹¹ genes are involved in the development of fat tissue and the metabolism¹²（新陈代谢） of glucose¹³（葡萄糖） , Sapienza believes it will be important to monitor these children long-term to determine whether they have higher rates of obesity or diabetes.

He notes that even though there were measurable differences in DNA methylation and gene³ expression between the two groups, only a small fraction（部分） of the assisted reproduction children were found to be outside the "normal" range.