There is good evidence that having a good level of folic acid in the bloodstream at the time of conception substantially reduces the risk of the baby having neural tube defects such as spina bifida. Public health authorities in UK, USA and elsewhere recommend that healthy women take 0.4 or 0.5 mg folic acid per day (this is available in many pre-pregnancy vitamin supplements) and those with risk factors for poor folic acid metabolism, such as women taking anti epileptic drugs or with MTHFR gene mutations should take 5.0 mg per day. What is important is to have it in the egg before it is fertilised.