A hi-tech scan can predict at an early stage which women are likely to have a miscarriage, say scientists.
Not all pregnancies are successful
US researchers hope the advanced type of ultrasound may eventually help to prevent many miscarriages.
In a study of 1,530 pregnant women, it predicted embryonic heart failure and miscarriage with 99% certainty just six weeks into pregnancy.
The technology has been developed by a private company, Diagnostic Ultrasound Consultants in Illinois.
The scan, which uses a probe inserted into the vagina, allows researchers to identify congestive heart failure in embryonic babies.
It works by measuring the speed of red blood cells moving through foetal blood vessels.
Lead researcher Dr Jason Birnholz said: "The chances the pregnancy will continue are very high, about 95%, when Doppler ultrasound confirms embryonic heart function at six weeks.
"Over 99% of pregnancies with an abnormal Doppler pattern do not continue."
"The cause of embryonic congestive heart failure - not enough oxygen reaching the heart - is much the same in embryos as it is in the elderly.
"I suspect that if the blood vessels that feed the placenta do not properly
form or are slightly delayed in development, the heart does not get the support
The study results suggested that embryonic congestive heart failure was
involved in 40% of miscarriages.
He said the test may eventually allow doctors to take action once a pregnant woman had been identified as being at risk of miscarrying.
Treatment might be as simple as providing extra oxygen to an expectant mother during the critical period early in her pregnancy.
Ruth Bender Atik, of the Miscarriage Association, said: "If this study can be replicated then we could have some really interesting and significant findings here."
Details of the research were presented at a meeting of the Radiological Society of North America.