Association Between Maternal Pre-Pregnancy Body Mass Index, Gestational Weight Gain and the Risk of Autism in Han Chinese Population

Background:  Autism is a neurodevelopment disorder with unclear etiology. Some previous studies suggested that maternal pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) might involve in the etiology of autism. However, the studies are still limited, and the findings need further replications. Furthermore, there are obvious ethnic disparities in BMI and GWG for the different genetic backgrounds, living environments and lifestyle. So it is necessary to validate in populations from different backgrounds.

Objectives:  The goal of this study is to explore the association between maternal pre-pregnancy BMI, GWG and the risk of autism in Han Chinese population.

Methods:  697 Han Chinese autistic children(599 male and 98 female,mean age 4.97±1.19 years) and their parents were recruited through a face to face interview,2200 age-matched unrelated typically developing (TD) children(1187 male and 1013 female,mean age 5.17±1.82 years) were recruited by using a web-based survey.

After removing the outliers, Student’s t-test and Chi square test were adapted to compare the demographic characteristics, the maternal BMI and GWG between case and control groups. Then we conducted binary logistic regressions to calculate the Odds Ratio (OR) for the relationship between pre-pregnancy BMI, GWG and the occurrence of autism.

All mothers of the enrolled children were classified as underweight, normal weight, overweight and obese according to the adult BMI classification standards for Chinese population. According to Chinese GWG recommendation, they were classified into inadequate weight gain, adequate weight gain and excessive weight gain based on their GWG.

Results:  The mean BMI of mothers with TD children was 20.30±2.27, and the mean BMI of mothers with autistic children was 20.50±2.25. The mean GWG of mothers with TD children was 15.04±5.81 kg , while 15.70±6.21kg of mothers with autism. There was a significant group difference in GWG (t=-2.526, p=0.012) and a minor but significant difference in maternal pre-pregnancy BMI (t=-2.015, p=0.044).

The results of logistic regression analyses showed that excessive weight gain during pregnancy was associated with autism risk in the whole samples (OR=1.475, 95%CI: 1.107-1.965) after controlling for the cofoundings. However, the inadequate gestational weight gain was not significantly associated with autism risk (OR=0.875, 95%CI: 0.690-1.110). One the other hand, the relationship between maternal pre-pregnancy BMI and autism was not found to be significant (normal weight was set as reference, underweight group: OR=0.901, 95%CI: 0.679-1.195; overweight group: OR=0.680, 95%CI: 0.445-1.038).

We further analyses the interaction between pre-pregnancy BMI and GWG by adapting stratification analyses with logistic model. And the results showed that neither inadequate (OR=1.225, 95%CI: 0.716-2.097) nor excessive GWG was significantly associated with autism risk for lean mothers. Excessive GWG would increase the risk of autism (OR=1.479, 95%CI: 1.059-2.066) for the normal pre-pregnancy weight mothers, might also significantly but more obviously increase the risk of autism (OR=2.479, 95%CI: 1.059-2.066) for overweight mothers.

Conclusions:  To our knowledge, this is the largest scale study in Chinese Han population. Our present study reported that maternal pre-pregnancy BMI might not be associated with autism risk, but excessive GWG might increase offspring autism risk among normal weight and overweight mothers