Maternal BMI linked to autism spectrum disorder risk in offspring
Children born to obese mothers are at increased risk of developing autism spectrum disorder (ASD) compared with those born to normal-weight mothers, according to data from a review and meta-analysis.
“The present findings provide strong persuasion for women to keep appropriate weight during pre-pregnancy or pregnancy, so as to reduce ASD risk in their offspring,” the investigators said.
In the current analysis, the risk of ASD in offspring was 36 (95 percent CI, 3 to 78) and 28 (19 to 36) percent higher for mothers who were obese and overweight, respectively, than for mothers with normal weight. Maternal underweight was not associated with increased ASD risk. [Sci Rep 2016;doi:10.1038/srep34248]
Of note is the presence of a linear dose-response relationship. Each 5-kg/m2 increment in maternal BMI increased the risk of ASD in offspring by 16 percent (1 to 33).
The analysis included 7 studies involving a total of 509,167 participants and 8,403 ASD cases. Begg’s and Egger’s tests showed no evidence of significant publication bias among the studies.
“Along with the nearly doubled world’s obesity rate between 1980 and 2008, the prevalence of ASD has also been increasing rapidly during the same period. While elevated awareness and updated diagnostic criteria of ASD might contribute to its increased prevalence, it is possible that the obesity epidemic may also play a role,” the investigators noted.
The causal pathway of the association between maternal BMI and ASD is not clear. All the same, the association may be simultaneously mediated by several factors, they added.
One is inflammation, which has been associated with neonatal brain damage. “[It] can induce a systemic foetal inflammatory response, which may contribute to white matter injury in the foetal brain,” they explained, “[so] it is plausible that the risk of mental disorders increases for children born to mother with overweight/obesity.”
Another is the involvement of diabetes. While obesity is a significant risk factor for diabetes, maternal diabetes itself can significantly increase the risk of ASD in the offspring, they said.
The investigators also noted that the supposed increase in ASD risk may be attributed to several mechanisms including hypoxia in the foetus, increased free-radical production, and impaired antioxidant defence system.
Dietary and nutritional factors play important roles in the development of both obesity and diabetes. These same factors, including fat and vitamin intake, may also contribute to the development of ASD, they added.
One limitation of the study is the inclusion of observational studies, which may be confounded by potential biases due to other factors that may contribute to ASD, such as physical exercise and intake of salt and saturated fat.
“Although all studies controlled for several factors, including maternal age at baseline, race, child’s sex, and birth year, the potential influences from residual or unmeasured confounding cannot be ruled out,” the investigators said, adding that further well-designed studies are needed to confirm the findings.