What causes congenital heart disease?

Only a minority of congenital heart disease (CHD) cases have a discernible genetic or syndromic cause, and maternal or intrauterine factors have been suspected by some as being significant. Coincidentally, two studies looking at different pregnancy-related influences, pre-eclampsia and hyperglycaemia, have been reported.

A study from Quebec looked at population data from the entire province, involving nearly 2 million births from 1989–2012 (Auger N et al. JAMA. 2015 doi:10.1001/jama.2015.12505). There were about 73 000 women with varying degrees of pre-eclampsia, and about 17 000 infants with CHD. They found a small but significant association between all types of CHD and pre-eclampsia (prevalence ratio 1.57; 95% CI 1.48 to 1.67). The association was stronger for those with early (<34 weeks gestation) rather than late pre-eclampsia. When CHD types were subdivided, the association was maintained only for non-critical rather than critical defects, which is rather difficult to explain.

In a much smaller study from California, researchers related actual blood glucose levels in pregnancy, rather than a diagnosis of diabetes, to specific heart defects (Priest JR et al. JAMA Pediatr 2015. doi:10.1001/jamapediatrics.2015.2831). They identified 277 pregnancies from 2003–2007 where the babies had either Tetralogy of Fallot (TOF) or …