The grades of evidence (I-III) and levels of recommendations (A-C) are defined at the end of the "Major Recommendations."
The following recommendations are based on good and consistent scientific evidence (Level A):
- Periconceptional folic acid supplementation is recommended because it has been shown to reduce the occurrence and recurrence of neural tube defects (NTDs).
- For low-risk women, folic acid supplementation of 400 micrograms per day currently is recommended because nutritional sources alone are insufficient. Higher levels of supplementation should not be achieved by taking excess multivitamins because of the risk of vitamin A toxicity.
- For women at high risk of NTDs or who have had a previous pregnancy with an NTD, folic acid supplementation of 4 mg per day is recommended.
- Maternal serum alpha-fetoprotein (AFP) evaluation is an effective screening test for NTDs and should be offered to all pregnant women.
The following recommendations are based on limited or inconsistent scientific evidence (Level B):
- Women with elevated serum alpha-fetoprotein levels should have a specialized ultrasound examination to further assess the risk of NTDs.
- The fetus with an NTD should be delivered at a facility that has personnel capable of handling all aspects of neonatal complications
The following recommendations are based primarily on consensus and expert opinion (Level C):
- The ideal dose for folic acid supplementation has not been appropriately evaluated in prospective clinical studies. A 400 microgram supplement currently is recommended for women capable of becoming pregnant.
- The route of delivery for the fetus with an NTD should be individualized because data are lacking that any one route provides a superior outcome.
Definitions:
Grades of Evidence
I Evidence obtained from at least one properly designed randomized controlled trial
II-1 Evidence obtained from well-designed controlled trials without randomization
II-2 Evidence obtained from well-designed cohort or case-control analytic studies, preferably from more than one center or research group
II-3 Evidence obtained from multiple time series with or without the intervention. Dramatic results in uncontrolled experiments also could be regarded as this type of evidence.
III Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees
Levels of Recommendations
Level A - Recommendations are based on good and consistent scientific evidence.
Level B - Recommendations are based on limited or inconsistent scientific evidence.
Level C - Recommendations are based primarily on consensus and expert opinion.
