Increasing dietary intake of folic acid could result in more women giving birth to twins after IVF treatment, UK researchers report. The research team, based at Aberdeen University, studied the likely impact of fortifying white flour with the vitamin. It is hoped that this proposed measure would cut the numbers of babies born in the UK with spinal cord defects such as spina bifida, since a lack of folic acid is one factor that increases the risk of such conditions. But according to the new research, published in the Lancet, it would also increase the number of twin babies born to women who undergo fertility treatment.

In the UK, women are advised to take 400 micrograms of folic acid (one of several different B vitamins) every day while trying to conceive, and during the first 12 weeks of pregnancy. The Food Standards Agency (FSA) has proposed adding folic acid to the nutrients currently used to fortify white flour, as has happened in the US since 1988. According to the Aberdeen researchers, the number of multiple births in the US has increased by 11-13 per cent following folic acid fortification.

The study involved measuring the folic acid intake and blood folate levels of 602 women undergoing IVF treatment. They also took DNA samples from the participants, and looked at variations in a key gene involved in processing folic acid, known as MTHFR. The scientists found that the likelihood of a twin birth rose with increasing intake of folic acid, although there was no link between folate levels and the chances of a successful pregnancy. They also discovered that women with two copies of the 'C' version of the MTHFR gene were less likely to have a baby after IVF, or to have had a previous pregnancy.

The team say that fortifying UK flour with folic acid would cause an extra 600 women per year to have twins after fertility treatment. But first author Paul Haggarty said that 'the high incidence of twin births associated with treatment for infertility could be reduced, while maintaining live birth rates, encouraging women not to exceed recommended doses of folic acid'. A spokesperson for the FSA said that any decision on adding folic acid to flour will take account of advice from the Scientific Advisory Committee on Nutrition, as well as other opinion, adding 'a watching brief will be kept for evidence in this area'.

Reproduced from BioNews with permission, a web- and email-based source of news, information and comment on assisted reproduction and human genetics, published by Progress Educational Trust.