A Case of Neural Tube Defect in Early Pregnancy Following Sulfasalazine Exposure Without Folic Acid Supplementation

Sulfasalazine is a widely used disease-modifying antirheumatic drug (DMARD) for inflammatory arthritis and is generally considered safe in pregnancy when co-prescribed with folic acid. However, its antifolate effects may influence folate metabolism, which is a recognised pathway associated with neural tube defects, particularly when folate supplementation is inadequate.

A 34-year-old woman conceived shortly after starting sulfasalazine without folic acid supplementation. Her pregnancy was complicated by fetal spina bifida and ventriculomegaly detected at 20 weeks' gestation, leading to termination. She had borderline-low serum folate before conception (3.7 μg/L). No other teratogenic exposures were identified.

This case highlights the importance of preconception counselling and adherence to high-dose folic acid (5 mg daily) in women of childbearing potential receiving sulfasalazine. While causality cannot be inferred, it draws attention to a potentially modifiable factor within the multifactorial aetiology of neural tube defects. It also reinforces that medications regarded as safe in pregnancy may still be associated with preventable risk when recommended supplementation is omitted.