The chances of having an autistic child increases by 67% in women who are obese when pregnant, revealed a study published in Pediatrics, suggesting that larger women lose weight before conceiving.

The study, which was partially funded by the U.S. National Institutes of Health, involved approximately 1,000 California children, aged from two to five, of which nearly 700 had autism or other developmental problems. Around 315 did not show signs of those problems.

Researchers also looked at their mothers' medical records to find the link between obesity and autism. The study showed that women who were obese during pregnancy were about 67% more likely to deliver autistic children, compared to healthy-weight women.

Obesity increases the odds of having child with autism to 1 in 53, while in the average woman’s odds of having a child with autism were 1 in 88. Explaining the relation between obesity and autism, study author Paula Krakowiak, an epidemiologist at the University of California, Davis said that excess blood sugar and inflammation-related substances in the blood of the mother damage the developing brain of the foetus.

"If you are planning a pregnancy you might want to think about losing weight, getting your exercise routine in order and controlling your blood sugar," advised Irva Hertz-Picciotto, senior author of the study and chief of the division of environmental and occupational health in public health sciences at UC Davis.

Dr Daniel Coury of Nationwide Children’s Hospital in Ohio said that the study has raised concern and further investigation is needed to confirm the link between obesity and autism.