The study of more than 6,600 women, aged 18-55, also found that underweight women can significantly reduce their risk of miscarriage in the first trimester by about 50 percent by taking supplements with folate or iron and by eating fresh fruits and vegetables every day.

Chocolate was also associated with reduced risk of miscarriage in this group of women.

The study is published in the current online edition of BJOG: An International Journal of Obstetrics and Gynecology.

Among the study's other findings:

• Women who weren't married or living with a partner had an increased risk of miscarriage.
• Women who had changed partners (for example, after having been pregnant before by a previous partner) had a 60 percent increased risk.
• Previous pregnancy termination increased the risk of subsequent miscarriage by 60 percent.
• Fertility problems were associated with a 41 percent increased risk.
• All types of assisted reproduction were associated with increased risk, particularly intrauterine insemination or artificial insemination.
• Women who said their pregnancies were "planned" had a 40 percent reduced risk of miscarriage.
• Women who had nausea and sickness in the first 12 weeks of pregnancy had about a 70 percent reduced risk.

"Our study confirms the findings of previous studies which suggest that following a healthy diet, reducing stress and looking after your emotional well-being may all play a role in helping women in early pregnancy, or planning a pregnancy, to reduce their risk of miscarriage," study author Noreen Maconochie, a senior lecturer in epidemiology and medical statistics, said in a prepared statement.

"The findings related to low pre-pregnancy weight, previous termination, stress and change of partner are noteworthy, and we suggest further work be initiated to confirm these findings in other study populations," Maconochie said.