Background Currently, there is mixed evidence regarding the effects on children when a parent is chronically ill. Research has also primarily been conducted with adolescent samples. This study investigated developmental vulnerabilities in young children of parents with chronic illness.

Methods This study used linked administrative data. The study population included children born in Western Australia during 2003–2004 (n=19 071; mean age 5.5 years). The outcome measure was a score in the bottom 25% on any of the five developmental domains (physical, social, emotional, communicative and cognitive) of the Australian Early Development Census (2009 collection). Parental chronic illnesses were identified from hospital and cancer registry records, during the period from 1 year prior to the child’s birth and until the end of 2009.

Results Higher odds of developmental vulnerabilities in physical, social, emotional and communication domains were observed for daughters of chronically ill mothers. Sons of chronically ill mothers had increased odds of language and cognitive difficulties. Risk level increased with each additional year of exposure to maternal chronic illness. Results also indicated increased odds of developmental vulnerabilities for children of mothers experiencing multiple compared with single chronic conditions; however, results were not statistically significant (all p>0.05). No association between fathers’ chronic illness and children’s developmental outcomes was found.

Conclusions Maternal chronic illness is associated with an increased risk of poor developmental outcomes for children, particularly daughters. Healthcare services have an important role to play in linking families into appropriate family-centred services to best support the needs of chronically ill mothers.