Currently, supplementation with folate and folic acid - the synthetic, bioavailable form of folate - is recommended to all women of child-bearing age since most neural tube defects (NTDs), including spina bifida and anencephaly, occur within the first 22 to 28 days of pregnancy, when the mother-to-be is not aware she is even pregnant.
Folic acid supplements after this time are too late to prevent neural tube defects and therefore fail to benefit women with unplanned pregnancies - more than half of all pregnancies in the US.
The benefits of continuing these supplements after the first trimester of pregnancy is less clear however. According to findings published in the European Journal of Obstetrics & Gynecology and Reproductive Biology, high dose folic acid supplementation during pregnancy, and particularly in the third trimester, may reduce the risk of preterm births by about 7 per cent.
On the other hand, the supplements did not affect the birth weight of the infants, report researchers from the Foundation for the Community Control of Hereditary Diseases in Budapest and Semmelweis University
“Minor increase in mean birth weight after high dose of folic acid supplementation during pregnancy would not be expected to result in too large babies; however, the significant reduction in the rate of preterm births may have great public health benefit,” wrote the researchers.
Population-based data of women 6,293 women taking folic acid, 169 taking multivitamins, and 311 women taking folic acid plus multivitamin supplements, were compared with data of 7,319 pregnant women not taking folic acid or folic acid-containing multivitamins.
Data showed that women taking folic acid alone had a 0.3 week longer gestation period, while folic acid alone in the third trimester was associated with a 0.6 week longer gestation, said the researchers.
They also report that the “rate of preterm births was significantly lower compared with the reference sample” at 7.6 compared 11.8 per cent, respectively. Folic acid alone in the third trimester associated with a rate of preterm births of 4.8 per cent, they added.
Commenting on the potential mechanism, the researcher said their “present hypothesis is that the maternal hyperhomocysteinemia has a role in the origin of preterm birth and the reduced maternal folate status associates with elevated homocysteine related placental vasculopathy which can be neutralized with high dose of folic acid supplementation during pregnancy particularly in the third trimester.
“An important task is to check the preterm birth reducing effect of folic acid in randomized controlled trial and to determine its optimal dose,” they concluded.
An overwhelming body of evidence links folate deficiency in early pregnancy to increased risk of neural tube defects (NTDs) - most commonly spina bifida and anencephaly - in infants.
This connection led to the 1998 introduction of public health measures in the US and Canada, where all grain products are fortified with folic acid - the synthetic, bioavailable form of folate.
Preliminary evidence indicates that the measure is having an effect with a reported 15 to 50 per cent reduction in NTD incidence. A total of 51 countries now have some degree of mandatory fortification of flour with folic acid.
However, similar measures in other countries have been opposed by concerns that the folate/folic acid may mask vitamin B12 deficiency, which leads to a form of neurological problems.
Source: European Journal of Obstetrics & Gynecology and Reproductive Biology
February 2010, Volume 148, Issue 2, Pages 135-140
“Possible association of folic acid supplementation during pregnancy with reduction of preterm birth: a population-based study”
Authors: A.E. Czeizel, E.H. Puho, Z. Langmar, N. Acs, F. Banhidy