Children conceived in winter have a greater risk of autism, study finds

May 5, 2011, University of California - Davis

An examination of the birth records of the more than 7million children born in the state of California during the 1990s and early 2000s has found a clear link between the month in which a child is conceived and the risk of that child later receiving a diagnosis of autism.

Among the children included in the study, those conceived during winter had a significantly greater risk of autism, the study found. The risk of having a child with an grew progressively throughout the fall and winter to early spring, with children conceived in March having a 16 percent greater risk of later autism diagnoses, when compared with July conceptions.

The researchers said the finding suggests that , for example, exposure to seasonal viruses like influenza, might play a role in the greater risk they found of children conceived during the winter having autism.

The study is published online today in the journal Epidemiology.

"The study finding was pronounced even after adjusting for factors such as maternal education, race /ethnicity, and the child's year of conception," said lead study author Ousseny Zerbo, a fifth-year doctoral student in the graduate group in epidemiology in the Department of Public Health Sciences in the UC Davis School of Medicine.

For the study, the researchers obtained the more than 7.2 million records for children born from January 1990 through December 2002 from the state of California Office of Vital Statistics. The researchers excluded some records because children did not survive to an age by which they typically would have been diagnosed with autism.

Other records were excluded because they were incomplete. For example, records that did not include adequate information from which to calculate the month of conception were excluded. The month of conception was calculated as the last date mothers reported having a plus two weeks.

The total number of records finally included in the study was approximately 6.6 million, or 91 percent of all births recorded during the study period. The children were followed until their sixth birthdays to determine whether they would develop autism.

The researchers identified which children were diagnosed with autism by matching birth records with those of children receiving services from the state Department of Developmental Services (DDS). Approximately 19,000 cases of autism were identified, with autism defined as "full syndrome" autism in the DDS records.

The study found that the overall risk of having a child with autism increased from month to month during the winter through the month of March. For the study, winter was considered the months of December, January and February. Each month was compared with July, with an 8 percent higher incidence in December, increasing to 16 percent higher in March.

Earlier studies' findings about autism risk and month of conception or birth have had varied results. Some, such as ones conducted in Israel, Sweden and Denmark, have found an increased risk of autism for children born in March. Studies conducted in Canada, Japan, the United States and the United Kingdom identified an increased risk of autism for children born in the spring. However, these studies were far smaller, most having a few hundred cases of autism, as compared with the large number of cases in California.

"Studies of seasonal variations can provide clues about some of the underlying causes of . Based on this study, it may be fruitful to pursue exposures that show similar seasonal patterns, such infections and mild nutritional deficiencies," said Irva Hertz-Picciotto, chief of the division of environmental and occupational health in the Department of Public Health Sciences in the UC Davis School of Medicine.

"However, it might be that conception is not the time of susceptibility. Rather, it could for instance be an exposure in the third month of pregnancy, or the second trimester, that is harmful," said Hertz-Picciotto, who also is researcher affiliated with the UC Davis MIND Institute. "If so, we might need to look for exposures occurring a few months after conceptions that are at higher risk. For example, allergens that peak in the spring and early summer."

The researchers said the study is a starting point for further inquiry. They noted that other seasonal occurrences include potential exposures to pesticides, such as those used in the home to control insects in rainy or warm months, and those used in agricultural applications.

Related Stories

Recommended for you

Researchers find infectious prions throughout eyes of patients with deadly sporadic Creutzfeldt-Jakob disease

November 20, 2018
By the time symptoms of sporadic Creutzfeldt-Jakob disease (sCJD) are typically discovered, death is looming and inevitable. But, in a new study, researchers at University of California San Diego School of Medicine with colleagues ...

Researchers a step closer to understanding how deadly bird flu virus takes hold in humans

November 19, 2018
New research has taken a step towards understanding how highly pathogenic influenza viruses such as deadly bird flu infect humans.

Infants born to obese mothers risk developing liver disease, obesity

November 16, 2018
Infant gut microbes altered by their mother's obesity can cause inflammation and other major changes within the baby, increasing the risk of obesity and non-alcoholic fatty liver disease later in life, according to researchers ...

New study shows NKT cell subsets play a large role in the advancement of NAFLD

November 16, 2018
Since 2015 it has been known that the gut microbiota could have a direct impact on nonalcoholic fatty liver disease (NAFLD), which affects up to 12% of adults and is a leading cause of chronic liver disease. In the November ...

Antibiotic prescribing influenced by team dynamics within hospitals

November 15, 2018
Antibiotic prescribing by doctors is influenced by team dynamics and cultures within hospitals.

Discovery suggests new route to fight infection, disease

November 14, 2018
New research reveals how a single protein interferes with the immune system when exposed to the bacterium that causes Legionnaires' disease, findings that could have broad implications for development of medicines to fight ...


Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet May 05, 2011
Somebody should tell Jim Carey this, maybe the pontificating prick could start preaching about conception times rather than vaccines.
not rated yet May 05, 2011
what happens in the body after several months w/ minimal UVb from sun exposure? Low vitamin D stores!!!

There is quite compelling evidence that autism spectrum disorder is, at least in part, linked to low maternal vitamin D3 levels and continued low levels in the child.

This release is more obfuscation re cholecalciferol (D3) and metabolites from the industrial medical complex - always follow the money!
not rated yet May 06, 2011
More evidence supporting the sunlight-deficiency theory of Autism.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.