Researchers in the US studied the effect of folic acid on nearly 40,000 pregnancies and found the B vitamin can reduce premature births by 50 to 70 per cent.
The Food Standards Agency and the Royal College of Obstetricians and Gynaecologists have called for cereal-based products to be enriched with folic acid in light of the research, say the papers.
It is thought this approach would be more successful than asking women to take vitamin supplements because many pregnancies are unplanned.
What is the research?
The reports were based on findings presented at the Society for Maternal-Fetal Medicine annual meeting in Texas earlier this month, funded by the US National Institute of Health (NIH).
University of Texas researchers analysed self-reported folate use in 38,000 women pregnant with one child. The length of gestation was recorded after each birth.
In pregnancies with an indication for early delivery such as placenta previa or pre-eclampsia, the result was excluded from the analysis.
Women taking folate for a year or more before conceiving had a 70 per cent lower risk of spontaneous premature delivery between 20 and 28 weeks gestation.
Risk of premature delivery between 28 and 32 weeks was reduced by 50 per cent.
Taking folate had no effect on pregnancies beyond 32 weeks or if folate was taken for less than a year before conception.
The researchers also noted that the effect of folate was no different in women with a previous preterm delivery.
What do the researchers say?
Lead researcher Dr Radek Bukowski said the scale and nature of the study helped to find definitive answers.
'Thanks to the depth and breadth of the NIH study, which included an early pregnancy ultrasound, we had highly accurate evidence of the gestational ages of the preterm deliveries,' he said.
What do other researchers say?
Professor Andy Shennan, spokesman for the charity Tommy's and an obstetrician at St Thomas' Hospital, London, said: 'It is difficult to see the plausibility of taking something as simple as folic acid having such a huge effect on a multifactorial syndrome.
'More likely is that women who take folic acid have other confounding factors which separate them from the comparative group.'
Professor Shennan said he would be amazed if the results were replicated in a prospective trial.
Janis Biermann, a spokesperson from the March of Dimes, a US non-profit pregnancy and baby health organisation, said: 'Practitioners should advise women that they should consume 400 micrograms of folic acid every day as part of a healthy diet.'
- Taking folic acid a year before conception reduces risk of pre-term births.
- In future, folic acid might be added to foods such as flour and bread.
- Until then, women of child bearing age are recommended to take 400 microgram of folic acid daily.
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