LONDON, May 5 (Reuters) Folic acid does not improve the chances of achieving a pregnancy but scientists said today it can increase the odds of twins when two embryos are transferred during fertility treatment.
Researchers at the Rowett Research Institute and Aberdeen University in Scotland found that women with high levels of folic acid were more likely to have twins following in vitro fertilisation (IVF).
''Basically the folic acid is increasing embryo survival, that is what we think is happening,'' said Dr Paul Haggarty, the lead author of the study published in The Lancet medical journal.
''We know that the embryo has an absolute requirement for folic acid and it will not develop if it doesn't have it,'' he explained.
Folic acid is a synthetic compound of folate, a B vitamin found in green leafy vegetables and liver. Women are advised to take supplements before conceiving and during the early months of pregnancy to reduce the risk of having a child with a neural tube disorder.
The serious birth defect occurs during the early development of the foetus when the spine does not close properly. Spina bifida, a defect of the spinal column, is the most common of them.
Haggarty and his team analysed the amount of folic acid in 602 women having fertility treatment. The women filled in questionnaires and the researchers measured folate intake from their diet and levels in their blood.
They found the likelihood of a twin birth after IVF rose with increased folate status in the women.
Nearly all of the women in the study took folic acid supplements.
To increase the chance of a pregnancy two embryos are often transferred to a woman during IVF treatment.
Haggarty said the finding is consistent with an increase in multiple births following fertility treatments in the United States after flour was fortified with folic acid in 1988.
''Our results suggest that the high incidence of twin births associated with treatment for infertility could be reduced, while maintaining live-birth rates, by encouraging women not to exceed recommended doses of folic acid,'' Haggarty said.
Recommended doses can vary slightly among countries. In Britain women trying to conceive are advised to take 400 micrograms a day before and during the first 12 weeks of pregnancy.
Reuters CH GC0949