You may be deficient in this vital nutrient for pregnancy even if supplementing.
Many pregnancy formulas available on the market do not have this vital nutrient in a form that can be utilized by many people who have a common genetic variation.
Folate or folic acid is a nutrient essential for healthy development of a foetus particularly in the first few weeks of pregnancy when a woman may not know she is pregnant.
If you have folate deficiency there is an increased risk of the neural tube not closing properly causing defects such as spina bifida.
Folate is the form found naturally in foods such as leafy greens and legumes.
Folic acid is the supplemental form added to food such as bread and found in most supplements. So essential is this nutrient that the Australian Government mandated in 2009 that all bread (except organic) must be fortified with folic acid.
It is recommended that all women planning for pregnancy begin supplementing at least one month before trying to conceive, ideally three months prior.
However variants on the methylenetetrahydrofolate (MTHFR) gene has been measured to occur in 31-39% of the population on one gene (heterozygous) and from 9-17% of population inheriting variants on both inherited genes (homozygous).  This polymorphism may interfere with folate metabolism and other metabolic pathways.
If you inherit the mutations on the MTHFR gene from both parents you may have an increased risk of your baby having spina bifida and certain pregnancy complications associated with raised homocysteine levels such as preeclampsia (elevated blood pressure), placenta detachment, increase miscarriage risk and low birth rate. Raised homocysteine levels is also associated with an increased risk of heart disease and stroke. 
How do I know if I have this gene variant?
A simple blood test can be conducted by your doctor and will determine if you have either the heterozygous (one) or homozygous (both) variants to the MTHFR gene from your parents. Unfortunately this test is currently not covered by Medicare in Australia, and will cost you about $60.00.
What to do if I have this variant?
Firstly this variant does not affect naturally occurring folate so include lots of folate rich foods in your meals such as asparagus, leafy greens, chickpeas, lentils and beans.
Choose a pregnancy formula that contains an activated form of folic acid, known as folinic acid to ensure adequate utilizable levels of this important nutrient.
This information is only partially correct. People with MTHFR should not consume any folic acid – it impedes the absorption of folate if you have the enzyme deficiency. MTHFR people need the active form, methylfolate. The prescription of high dose folic acid for women (or men) with MTHFR is an outdated treatment method.
Thank you for your comments. As I noted in the post, folic acid cannot be converted and thus anyone with this mutation needs to be taking an activated supplemental form such as folinic acid which bypasses the need for this enzyme to be converted into folate.