Since the embryo’s neural tube closes between the 24th and 28th day after conception ​ — long before many women realize that they are pregnant — ​ some women who are planning to become pregnant take folic acid.
Kuna loote neuraaltoru sulgub 24. – 28. päeval pärast viljastumist – palju varem, kui naine oma rasedusest üldjuhul teadlikuks saab –, tarvitavad mõned rasestuda kavatsevad naised foolhapet.