Sex ratio at birth is associated with type 1 diabetes characteristics

Aims: To assess the association between maternal diabetes characteristics and sex ratio at birth (SRB) in women with type 1 diabetes mellitus. Methods: We performed a case–control study. The study subjects were infants born alive to women with type 1 diabetes and singleton pregnancies. Cases and controls were defined as male and female newborns, respectively. SRB was analysed according to diabetes-related characteristics adjusting in a logistic regression analysis for maternal characteristics known to affect SRB in the general population. Results: The observed SRB (238 males/468 live births = 0.509) did not differ from the expected. In the logistic regression analysis, SRB was significantly associated with three diabetes characteristics: (1) diabetes duration, with odds ratios (ORs) for a live male newborn = 1.22 (95 % confidence interval (CI), 0.66–2.24 for ≤5 years, OR 2.79 (95 % CI 1.36–5.74) for >20 years; (2) mean first-trimester glycated haemoglobin, with OR 1.98 (95 % CI 1.09–3.62) for ≤6.7 % (50 mmol/mol) and OR 2.61 (95 % CI 1.16–5.85) for >8.2 % (66 mmol/mol) and (3) mean first-trimester insulin dose, with OR 0.70 (95 % CI 0.36–1.38) for ≤0.5 IU/kg/day and OR 0.18 (95 % CI 0.05–0.59) for >1.0 IU/kg/day. Conclusions: We conclude that SRB in this cohort is independently associated with three diabetes characteristics. These associations are to be confirmed.