SOGC CLINICAL PRACTICE GUIDELINEPre-conception Folic Acid and Multivitamin Supplementation for the Primary and Secondary Prevention of Neural Tube Defects and Other Folic Acid-Sensitive Congenital Anomalies
Section snippets
Summary Statement
In Canada multivitamin tablets with folic acid are usually available in 3 formats: regular over-the-counter multivitamins with 0.4 to 0.6 mg folic acid, prenatal over-the-counter multivitamins with 1.0 mg folic acid, and prescription multivitamins with 5.0 mg folic acid. (III)
Recommendations
- 1.
Women should be advised to maintain a healthy folate-rich diet; however, folic acid/multivitamin supplementation is needed to achieve the red blood cell folate levels associated with maximal protection against neural tube defect. (III-A)
- 2.
All women in the reproductive age group (12–45 years of age) who have preserved fertility (a pregnancy is possible) should be advised about the benefits of folic acid in a multivitamin supplementation during medical wellness visits (birth control renewal, Pap
INTRODUCTION
It has been estimated that 4% to 5% of babies are born with a serious congenital anomaly1; 2% to 3% will have congenital anomalies (malformations, deformations or disruptions) that can be recognized prenatally by non-invasive ultrasound screening or anticipated through invasive diagnostic testing and 2% will have developmental or functional anomalies and minor congenital anomalies recognized at birth or during the first year of life.1 Folic acid, taken orally prior to conception and during the
FOLIC ACID SUPPLEMENTATION AND THE PREVENTION OF BIRTH DEFECTS
The initial NTD translational research study investigated folic acid supplementation for recurrence prevention of NTDs in a randomized double-blind clinical trial involving 1195 completed high risk pregnancies in women from 33 centres.2 The NTD recurrence rate decreased from 3.5% in a non-supplemented group to 1% for women randomized to the group receiving an oral 4 mg folic acid supplementation daily prior to pregnancy and throughout the first 6 weeks of pregnancy.
The second NTD translational
ORAL FOLIC ACID SUPPLEMENTATION PREGNANCY CARE
Oral pre-conception folic acid dietary intake or supplementation is required as it is the primary source for the trans-placental transfer of folate/folic acid to the embryo/fetus. No specific studies have been published looking at the embryonic cell folate availability in humans during this embryonic target period of 0 to 8 weeks (conception to 10 gestational weeks). Canadian researchers have made strong contributions in this area of prevention.41., 42., 43., 44., 45., 46., 47., 48., 49., 50.,
Background for NTD Prevention
Neural tube defects are severe congenital anomalies that occur due to a lack of neural tube closure at either the upper, middle, or lower portion of the spine in the third to fourth week after conception (day 26 to day 28 post-conception).77
In Canada, the prevalence of NTDs in newborns has declined since 1998 due to food fortification and increased vitamin supplementation,78., 79., 80. as well as to an increase of prenatal diagnosis/termination.45., 46.
Recurrence risks may reflect the genetic
Benefit
Folic acid, in a 0.4 to 1.0 mg daily dose60., 150., 151., 152. is not known to cause demonstrable harm to the developing fetus or to the pregnant woman. The risk of maternal or fetal toxicity from oral folic acid intake due to vitamin supplements and/or fortified foods is low. Folic acid is a water soluble vitamin, so any excess intake is anticipated to be excreted in the urine.
Folic acid has not been shown to promote or to prevent breast cancer.153., 154., 155.
Ovarian cancer studies suggest
Benefit
Pediatric ongoing health benefits have been identified following prenatal multivitamin supplementation before and in early pregnancy.40., 128. Maternal use of prenatal multivitamins is associated with a decreased risk for pediatric brain tumours (OR 0.73, 95% CI 0.60 to 0.88),40., 146., 180. neuroblastoma (OR 0.53, 95% CI 0.42 to 0.68),40 leukemia (OR 0.61, 95% CI 0.50 to 0.74),40., 147. Wilms’ tumour,142 primitive neuroectodermal tumours,145 and ependymomas.145 It was stated that it is not
COUNSELLING AND FOLIC ACID SUPPLEMENTATION
Canadian data indicates clear socio-demographic differences among women with respect to their knowledge and use of folic acid. Although most women understood the benefits of folic acid supplementation, greater than 33% did not take folic acid supplements prior to becoming pregnant and less than 50% supplemented according to national guidelines. Targeted education and other interventions to improve folic acid use in younger women and women with lower socio-economic status is recommended.189
Han
SUMMARY
Folic acid (in the diet and/or as a prenatal oral supplement) with a multivitamin/micronutrient has been shown to decrease or minimize specific congenital anomalies including neural tube defects with associated hydrocephalus, oral facial clefts with or without cleft palate, congenital heart disease, urinary tract anomalies, and limb defects, as well as some pediatric cancers. The 1998 public health initiative for fortification of flour has been very beneficial with respect to primary prevention
ACKNOWLEDGEMENTS
Expert opinion and guideline review were obtained from the Public Health Agency of Canada and Motherisk.
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This Clinical Practice Guideline was prepared by the Genetics Committee, reviewed by the Family Physician Advisory Committee, and approved by the Executive and Board of the Society of Obstetricians and Gynaecologists of Canada.
Disclosure statements have been received from all contributors.
This document reflects emerging clinical and scientific advances on the date issued and is subject to change. The information should not be construed as dictating an exclusive course of treatment or procedure to be followed. Local institutions can dictate amendments to these opinions. They should be well documented if modified at the local level. None of these contents may be reproduced in any form without prior written permission of the SOGC.