Very underweight women are 72 per cent more likely to suffer a miscarriage in the first three months of pregnancy.
Researchers at the London School of Hygiene and Tropical Medicines also found that eating fruit, vegetables and chocolate could reduce the risk of miscarriage among underweight women.
Thestudy examined the association between biological, behavioural and lifestyle risk factors and the likelihood of miscarriage, which affects about 250,000 women a year.
The findings suggested that those classed as very underweight - with a body mass index of less than 18.5 - were much more likely to miscarry in the first trimester.
The research also revealed that the two-thirds of women who took vitamin supplements early on in their pregnancy reduced the miscarriage risk by about a half - with the effect most pronounced for those women who took folic acid, or iron and multivitamins.
A daily intake of fresh fruit and vegetables also halved the odds, and eating chocolate seemed to lower the likelihood of a miscarriage.
