Birth Defects from Valproate Lower in Bipolar Disorder than in Epilepsy
The anticonvulsant valproate increases the risk of serious birth defects in fetuses exposed to it. However, a 2017 report by ANSM, France’s agency for health and product safety, and its national insurance fund for employed workers shows that these risks are lower for women taking valproate for bipolar disorder than for women taking valproate for epilepsy.
In France, the risk of a major fetal malformation was 10.2 per 1000 women in the general population, about twice that (22.2 per 1000) in women taking valproate for bipolar disorder, and about 4 times higher (46.5 per 1000) in women taking valproate for epilepsy. The authors suggest that treatment for bipolar disorder may be more likely to be interrupted during pregnancy, and this could explain the different levels of risk by diagnosis.
Among the risks of defects in the fetuses of women being treated with valproate for epilepsy, the risk of a ventricular septal defect (a hole in the wall separating the lower heart chambers) was 11.2% compared to 2.7% in fetuses not exposed to valproate, while risk of an atrial septal defect (a hole in the wall separating the upper heart chambers) was 19.1% in the fetuses of those prescribed valproate for epilepsy compared to 1.9% in unexposed fetuses. Risk of hypospadias (placement of the urethra opening on the underside of the penis rather than its end) was 22.7% compared to 4.8% in the general population.
Risks of a major malformation were dose dependent in those with epilepsy (but interestingly, not in those with bipolar disorder), meaning the more valproate patients with epilepsy took, the higher their risk of a fetus with birth defects.
The only birth defects that were more common in the fetuses of women taking valproate for bipolar disorder than in fetuses not exposed to valproate were hypospadias (17.5% risk compared to 4.8% in the general population) and craniostenosis, a deformity of the skull (4.2% risk compared to 0.4% in the general population).
The relative safety of valproate in women being treated for bipolar disorder compared to those being treated for epilepsy is good news for some. However, fetal exposure to valproate has also been linked to deficits in cognitive development.
The risk of spina bifida, which causes lifetime paralysis, in a fetus may no longer be such a catastrophic issue for women taking valproate for bipolar disorder (where the risk did not exceed that of the general population), as was once assumed based on data from women with epilepsy (where the risk is usually 2-4%, but was 8% in this French study). This may be of some comfort to women with bipolar disorder who require valproate treatment to remain stable and wish to become pregnant or in those who experience an unplanned pregnancy.
