Numerous studies have linked prenatal folic acid with lower risks of giving birth to a baby with neural tube defects (NTDs). And now, Norwegian researchers report in JAMA that folic acid supplementation early during pregnancy may curb the odds of delivering a baby with an autistic disorder.

The autism spectrum disorders (ASDs)

Autism is a group of developmental disabilities, collectively known as the ASDs. As the term ‘spectrum’ suggests, the disorder can cause mild to severe social, communication (verbal and/or non-verbal) and behavioural impairments. There are 3 main types of ASDs:

  • Autistic disorder (also known as “classic” autism)
  • Asperger Syndrome
  • Pervasive Developmental Disorder – Not Otherwise Specified (PDD-NOS; also called “atypical” autism)

Rett syndrome and Childhood disintegrative disorder are two rare, severe autistic-like conditions.

Folic acid — a brief overview of this essential vitamin

Also known as folate in its natural form, this B-group vitamin is essential for cell growth and for the proper development of the baby’s neural tube and spinal nerves. Pulses, green leafy vegetables, edamame, wheat germ, asparagus, oranges and papayas are rich in folate.

Study details

The researchers selected a sample of 85,176 children born between 2002 and 2008 from the population-based, prospective Norwegian Mother and Child Cohort Study (MoBa). The exposure of primary interest was maternal supplementation of prenatal folic acid from 4 weeks before to 8 weeks after pregnancy “defined as the first day of the last menstrual period before conception”. The children were followed-up for about six years.

This time period was chosen because of the neurodevelopmental processes that occur within the first few days post-conception. For instance, the foetus’ brain and neural tube structure are formed in the first 28 days after pregnancy — often before the woman even knows she’s pregnant. Moreover, previous studies provide evidence that folic acid supplementation during this critical window prevents serious defects of the brain (anencephaly) and spine (spina bifida).

Study findings

During the follow-up years, 270 children were diagnosed with ASDs — 114 with autism, 56 with Asperger syndrome and 100 with an unspecified autism disorder.

The children whose mothers took folic acid pills early during pregnancy had a 39 percent lower risk of developing an autistic disorder compared to those whose mothers did not. It is speculated that the vitamin could blunt a genetic predisposition for autism or enhance other protective factors during pregnancy.

No link was found between folic acid and either Asperger syndrome or unspecified autism disorder. The authors explained that the number of children with Asperger syndrome was not large enough to obtain significant statistical power in the analyses.

Moreover, while folic acid appeared to offer a protective effect even if not taken until early pregnancy, taking the supplement at mid-pregnancy offered no such protection.

“The study does not prove that folic acid supplements can prevent childhood autism. But it does provide an indication that folic acid might be preventive,” stated study lead author Dr. Pal Suren, from the division of epidemiology at the Norwegian Institute of Public Health in Oslo.

The NHS recommends that women take a daily 400mcg folic acid tablet while trying to conceive and 12 weeks into pregnancy. Women who didn’t take folic acid before they conceived should start as soon as they know they’re pregnant.


    Surén et al (2013) Association between maternal use of folic acid supplements and risk of autism spectrum disorders in children. JAMA. 309(6):570-577.