A UK study found women with a history of miscarriage who have early bleeding in their next pregnancy could benefit from the hormone progesterone.
Researchers from the University of Birmingham said an estimated 4700 babies' lives per year in the UK could be saved.
The research involved 4153 pregnant women who presented with early pregnancy bleeding at 48 UK hospitals.
They were randomly assigned by computer into one of two groups - one group of 2079 women who were given 400mg of progesterone twice daily as a vaginal pessary, while the other group of 2074 were given a placebo.
While the study did not show that progesterone could help all women who suffered early pregnancy bleeding, it was found to help those who had suffered a previous miscarriage.
Of the 777 women given progesterone who had previously had one or two miscarriages, 591 (76 per cent) went on to have a live birth, compared with 534 women out of 738 in the placebo group (72 per cent).
The benefit was greater for the women who had suffered three or more miscarriages, with a 15 per cent increase in the live birth rate in the progesterone group compared with the placebo group.
Of 137 women with three or more previous miscarriages, 98 (72 per cent) went on to have a live birth, compared with 57 per cent (85 out of 148) of women in the placebo group.
The PRISM trial, which was funded by the National Institute for Health Research (NIHR) and published in the New England Journal of Medicine, was the largest of its kind.
"This treatment could save thousands of babies who may have otherwise been lost to a miscarriage." said Arri Coomarasamy, professor of gynaecology at the University of Birmingham and director of Tommy's National Centre for Miscarriage Research.
Dr Adam Devall, senior clinical trial fellow at the University of Birmingham and manager of Tommy's National Centre for Miscarriage Research, said: "Miscarriage is a common complication of pregnancy, affecting one in five women, and vaginal bleeding in early pregnancy is associated with a one in three risk of miscarriage.
"Several small studies have suggested that administering progesterone, a hormone essential for maintaining a pregnancy, may reduce the risk of miscarriage in women presenting with early pregnancy bleeding."
