Perinatal risk factors for early onset of Type 1 diabetes in a 2000–2005 birth cohort

Aims To examine perinatal risk factors for the onset of Type 1 diabetes before 6 years of age, in a 2000–2005 Australian birth cohort. Methods Data from longitudinally linked delivery and hospital admission records (until June 2007) were analysed. Diabetes in mothers and children was identified from International Classification of Diseases 10 diagnosis codes in the hospital records. Results There were 272 children admitted to hospital with a first diagnosis of diabetes out of 502 040 live births. Incidence for the infants born in 2000 was 16.0 per 100 000 person‐years. Maternal Type 1 diabetes was a significant risk factor [crude relative risk (RR) 6.33], but maternal Type 2 diabetes and gestational diabetes were not significantly associated with diabetes in the child. Late preterm birth (34–36 weeks) (RR 1.64) and caesarean section (RR 1.30) increased the risk of a diabetes admission. Size‐for‐gestational‐age was significantly associated with onset of diabetes (small‐for‐gestational age RR 0.48), but neither birth weight categories nor birth weight as a continuous variable were associated with risk of diabetes. Increasing maternal age was associated with an increased risk of diabetes in the child (RR 1.13 for each additional 5 years of age). Conclusions This study identified risk factors associated with onset of Type 1 diabetes before 6 years of age, in a recent birth cohort. Size‐for‐gestational‐age had a consistent association with risk of early onset of Type 1 diabetes, small size being protective. Size‐for‐gestational‐age measures should be preferred to birth weight thresholds when assessing risk of diabetes.