Does folic acid need to start before pregnancy?

What the evidence says

Folic acid is a B vitamin. It helps prevent neural tube defects, which are serious problems with a baby's brain or spine. The neural tube forms and closes very early, usually within the first month after conception, often before a person even knows they are pregnant.

Because of this early timing, health experts say folic acid needs to be on board before pregnancy starts, not just after a positive test. Health Canada and the Society of Obstetricians and Gynaecologists of Canada recommend that anyone who could become pregnant take a daily multivitamin with 400 mcg (0.4 mg) of folic acid, starting at least two to three months before trying to conceive.

This is also why Canadian guidance says folic acid matters even if pregnancy is not being planned right now. Many pregnancies are unplanned, so taking a low daily dose ahead of time acts like a safety net.

Some people need more than the standard dose. Higher amounts, often 1 mg or more, may be recommended earlier, for example three months or more before conception, for those with a personal or family history of neural tube defects, certain medical conditions like diabetes, or use of specific seizure medications. A health care provider can advise on the right dose and timing for individual situations.

In short, starting folic acid only after finding out about a pregnancy misses the window when it does the most good. Starting it beforehand, and continuing through early pregnancy, is what the evidence supports.