A new study suggests that ‘test tube babies’ or those conceived through in vitro fertilization (IVF) were at risk of mental retardation.

Sven Sandin, lead author of the study and a biostatistician from Stockholm University in Sweden, and his colleagues analyzed the records of about 2.5 million children conceived through IVF between years 1982 and 2007 as well as the Swedish registry that identified children aged four with developmental disorders. From this population, 6,959 were diagnosed with autism disorder while 15,830 were diagnosed with mental retardation.

This means that 1 out of 100 IVF babies may grow either autistic or retarded.

There were previous studies made associating IVF conception with preterm delivery but there were fewer studies made looking at the mental development of the infants born through different methods of IVF. Those studies were not able to fully establish the link between mental disorder and IVF due to contrasting results.

In vitro fertilization (IVF) is a process in which the egg is fertilized by the sperm outside the body. Babies conceived through this process are dubbed as ‘test tube babies’ because the fertilization happens in a glass or test tube inside a medical laboratory. The pregnancy success rate of this process is only at 50 percent but not all were born alive. Only 8 out 10 survive. As the women get older too, the chance of pregnancy decreases to 20.5 percent. This is according to the 2009 data of the U.S Society for Reproductive Medicine.

The researchers admitted that their study had limitations and needs further analysis to fully establish their conclusions. They were not able to include other factors that may trigger mental disorders to children such as the miscarriage history of the mother, education, and socioeconomic status of the parents.

They concluded that the occurrence of mental disorders was low and that the risk to developing those was small.

However, a published editorial by Marcelle Cedars, director of the Division of Reproductive Endocrinology and Infertility, University of California-San Francisco, highlighted that though the risk is small, the study was able to prove that autism and retardation may occur using unnatural fertilization process. She appealed to have further research done despite the slight risk.

The study was published on the July 2 issue of JAMA Network.