Exposure to folic acid antagonists during pregnancy is associated with a higher risk of placenta-mediated adverse outcomes such as preeclampsia, placental abruption, fetal growth restriction or fetal death reports a retrospective cohort study published in CMAJ http://www.cmaj.ca/press/pg1263.pdf .
Folic acid antagonists include a broad range of drugs used to treat epilepsy, mood disorders, hypertension and infections. As approximately 50% of pregnancies in industrialized countries like Canada are unplanned, there is a risk of unintended exposure to these medications.
The study, conducted by researchers from Ottawa, Montreal, Saskatoon and Hunan, China looked at 14 982 women who had taken folic acid antagonists one year prior to delivery and 59 825 women who did not. Dr. Shi Wu Wen and co- researchers found that maternal exposure to folic acid antagonists was associated with a slightly higher risk of adverse pregnancy outcomes. They suggest re-classifying some folic acid antagonists and recommend increased folic acid supplements for women requiring folic acid antagonists during pregnancy.
In a related commentary http://www.cmaj.ca/press/pg1243.pdf , Dr. Joel Ray suggests the research study presents some "thought-provoking findings, but the results may not be ready for adoption by clinical practitioners or drug policy makers." He cites some real concerns with the study design and the need for clinically relevant finding as cautions about translating findings into practice.
Canadian Medical Association Journal