Figure 1.

Spline model for continuous body mass index (BMI). When modeled using restricted cubic splines, the association of BMI with autism spectrum disorder (ASD) risk showed an increasing linear trend (p value for nonlinearity = .53). Although the plot shows a slight U-shape with a potential increase in ASD risk among women who were underweight, we note that the confidence bands below a BMI of 21 are extremely wide, showing no statistically significant difference as confirmed by the test for nonlinearity. GP, general population control; OR, odds ratio.