Folate leads to multiple births: "Women undergoing in-vitro treatment who take large doses of folic acid, a supplement designed to prevent foetal defects, may be far likelier to give birth to twins than to singletons, a study suggests. Only about one in every five attempts at in-vitro fertilisation (IVF) results in a live birth, so doctors often try to boost the success rate by implanting several embryos at a time. But multiple pregnancies run a higher risk of congenital abnormalities, foetal growth retardation and miscarriage, so understanding the causes and risks of twinning and reducing it if possible is useful. In a paper that appears in next Saturday's issue of The Lancet, researchers at the University of Aberdeen, Scotland, recruited 602 women undergoing IVF treatment and assessed levels of folic acid in their blood. The study sought to establish the correlation between high levels of folic acid and multiple pregnancies and only speculated as to possible underlying causal links. Folic acid, also called folate or vitamin B9, is widely recommended as a supplement for women who want to conceive, as it protects against spina bifida and other so-called neural tube abnormalities. The investigators found women with high levels of folic acid in their blood plasma were 52 per cent likelier to have twins than singletons, in cases where multiple embryos were implanted". [Twins are usually greatly treasured so this is not a disaster story]