March 30, 2009 -- Despite a possible connection between prenatal stress and autism, researchers in Denmark say the pain of losing a loved one during or just before pregnancy does not increase the baby's risk of autism later in life.
Medical evidence has suggested that emotional trauma during or in the year prior to pregnancy may make a woman more likely to give birth to a child who will later develop autism. Although the overall cause of autism remains highly debated and largely unknown, many experts contend it is likely the result of multiple genetic and environmental causes, particularly those that occur early in life.
Animal studies have shown that maternal stress -- stress in the mother during pregnancy -- can significantly influence the brain development of the baby while in the womb. Additional research has linked stress during pregnancy to social and emotional problems and schizophrenia, according to background information in the journal article.
However, little data exist on the effect of prenatal stress and a woman's chances of having her child develop autism later in life.
To examine the link, Jiong Li, MD, PhD, and colleagues looked at autism rates in more than 1.4 million babies (all single births) born in Denmark from 1978 to 2003. The researchers divided the children into two groups: Those whose mothers lost a close relative during pregnancy or in the year prior to getting pregnant ("exposed" group), and those who did not ("unexposed" group). There were about 37,000 babies in the exposed group.
"We believe bereavement is a good indicator of severe stress," the researchers write in the journal Pediatrics. "A large body of literature has demonstrated bereavement to be one of the most stressful life events, leading to a surge of stress hormones."
The researchers followed the children for 28 years, or until their death, age of autism, or departure from the study, whichever came first, and compared autism diagnosis between the two groups. Autism information was obtained from the Danish Psychiatric Central Register.
Li's team failed to find a strong association between maternal bereavement and autism risk. The news could offer reassurance to mothers-to-be who worry that such stress could affect the health of their baby.