Spotlight on type 1 diabetes and pregnancy

Two recent studies looked at adverse effects on offspring of type 1 diabetes during pregnancy.

One study, published as a research letter in the July 3 JAMA, examined rates of autism spectrum disorder (ASD) among children born at Kaiser Permanente Southern California hospitals from Jan. 1, 1995, through Dec. 31, 2012. The retrospective study included 419,425 children (51% male), including 621 exposed to maternal type 1 diabetes, 9,453 exposed to maternal type 2 diabetes, 11,922 exposed to gestational diabetes diagnosed by 26 weeks' gestation, and 24,505 exposed to gestational diabetes diagnosed after 26 weeks. In total, 5,827 of the children were diagnosed with ASD during a median follow-up of 6.9 years. Unadjusted average annual ASD incidence rates per 1,000 were 4.4 with maternal type 1 diabetes (for an adjusted hazard ratio [aHR] of 2.36 compared to no diabetes); 3.6 with type 2 diabetes (aHR, 1.45); 2.9 with gestational diabetes by 26 weeks (aHR, 1.30); 2.1 with gestational diabetes after 26 weeks (aHR, 0.99); and 1.8 with no diabetes. “These results suggest that the severity of maternal diabetes and the timing of exposure (early vs late in pregnancy) may be associated with the risk of ASD in offspring of diabetic mothers,” the authors said.

Another study, published by The BMJ on July 5, compared birth defects among 2,458 Swedish infants of mothers with type 1 diabetes and 1,159,865 infants of mothers without diabetes. It found 122 cases of major cardiac defects in the infants of women with type 1 diabetes, with the risk varying by the mother's HbA1c within three months of conception. Compared with 15 major cardiac defects per 1,000 infants of mothers without diabetes, the rates among infants of women with type 1 diabetes were 33 per 1,000 with an HbA1c below 6.5%, 49 per 1,000 for 6.5% to below 7.8%, 44 per 1,000 for 7.8% to below 9.1%, and 101 per 1000 for 9.1% or higher. The study also found 50 cases of major noncardiac defects among the infants of mothers with type 1 diabetes but no significant association between type 1 diabetes and these defects at any level of HbA1c, although the authors noted that statistical power for this outcome was limited and only live births were included. Given that the risk of cardiac defects was more than doubled even for infants of women with HbA1c levels under 6.5%, “these findings may indicate that yet lower target glycated haemoglobin levels than are currently recommended might be advisable,” the study authors wrote, although they cautioned that potential benefits should be weighed against the risks of intensified insulin treatment, such as hypoglycemia.