Compared to other mothers, mothers of children with autism spectrum disorder (ASD) or intellectual disability (ID) have higher rates of treatment episodes for psychiatric disorders. We aimed to estimate the maternal burden of care by comparing the length of hospitalisations for psychiatric disorders and the treatment rates for psychiatric disorders after the birth in mothers of children with ASD/ID and no psychiatric history to that of other mothers with no psychiatric history. Mothers of children with ID of known cause (not Down syndrome) and mothers of children ASD without ID emerged as particularly vulnerable. Mothers of children with Down syndrome were resilient. The development of specialised organisations to provide support to mothers of children with ID of known cause (not Down syndrome) and mothers of children with ASD without ID could assist them to maintain their mental health.