According to a study published in the Journal of the American Medical Association, a method of in-vitro fertilization (IVF) known as ICSI (Intra Cytoplasmic Sperm Injection) increases the risk for the resulting child of developing mental retardation. The study covered a sample of 2.5 million children born in Sweden between 1982 and 2007. In this group, the cases of 30,959 children born after in-vitro fertilization were looked into more closely by the researchers based in the United Kingdom and the United States. They compare six different IVF methods used in Sweden and the use or non-use of frozen embryos.
ICSI is a method used in almost one half of IVF procedures, in particular in the case of male infertility. It consists of injecting the selected sperm directly into the oocyte.