Neural tube defects

Joel Ray and associates1 found that in Ontario the risk of neural tube defects was higher among First Nations women than among women of other ethnic origins, independent of age, body weight and pregestational diabetes. The prevalence of type 2 diabetes among First Nations adolescents in Manitoba and northwestern Ontario is increasing, and the poor diabetes control and poor nutrition that often occur in these young women may constitute additional risk factors for neural tube defects in future offspring.

The high rate of adolescent pregnancy and the additional risk of neural tube defects in First Nations women raise the question of whether all young First Nations women with type 2 diabetes should receive advice regarding dietary and supplemental folic acid.

Several recent clinical practice guidelines have included recommendations on folic acid supplementation for mothers at high risk for neural tube defects. In 2003 the Society of Obstetricians and Gynaecologists of Canada recommended that all “women with insulin-dependent diabetes” should be advised to take high-dose folic acid (4–5 mg, taken as a pure folic acid supplement).2 In 2002 Health Canada recommended that “women with diabetes” reduce the risk of neural tube defects in their babies by ensuring optimal diabetes control in the periconceptional period, noting that high-dose folic acid may or may not provide added benefit.3 The 2003 guidelines of the Canadian Diabetes Association reviewed the evidence for reduction of the risk of neural tube defects with folic acid supplementation in diabetic pregnancies but stopped short of any specific recommendation regarding folic acid.4 A 1997 recommendation by the Canadian Paediatric Society made no special recommendation for women with diabetes,5 but this position statement is currently under revision.

Young First Nations women with type 2 diabetes may have multiple factors putting their future offspring at high risk for neural tube defects, namely ethnicity, poor diabetes control and poor nutrition. The evidence for risk reduction with optimal preconception control of diabetes in young women with type 1 diabetes3 is probably applicable to young First Nations women with type 2 diabetes. However, the other unique clinical features of this population necessitate the development of specific consensus guidelines for folic acid supplementation for prevention of neural tube defects.