In an ectopic pregnancy the foetus develops outside of the womb
Women with ectopic pregnancies have a lower level of a particular protein and this could be used to create a simpler and more effective test, a study finds.
At present, finding out if a foetus is developing outside of the womb as occurs in these pregnancies requires ultrasounds and several blood tests.
Most cases are not spotted at a patient's first hospital visit.
But Edinburgh University scientists say the protein activin B could be key to early diagnosis and treatment.
Ectopic pregnancies put the mother at risk because of the possibility that the area where it is growing - usually the fallopian tube but sometimes the cervix or ovaries - can rupture, causing potentially fatal internal bleeding.
In the UK, five women a year die of this - in the developing world, one in 10 of these pregnancies ends in the death of the mother.
So to protect women's health, these pregnancies are usually terminated once the diagnosis is confirmed.
Investigating whether a pregnancy is ectopic costs the NHS around £9m per year, and also places immense strain on the mother.
Make it simple
But Edinburgh researchers writing in the journal Human Reproduction say they have established that women with these pregnancies have a much lower level of the protein known as activin B. They hope now to develop a simple diagnostic test.
Dr Andrew Horne, of the University of Edinburgh's Centre for Reproductive Biology, said: "Diagnosing an ectopic pregnancy is incredibly complex yet detecting the condition early on can ease the emotional trauma of those affected.
"Early diagnosis can also prevent future fertility problems and improve the effectiveness of treatment as well as save the NHS millions of pounds. Understanding how proteins are expressed is pivotal in developing a simple blood test that could be used to detect an ectopic pregnancy."
The Ectopic Pregnancy Trust welcomed the research.
"Studies that give us the tools to establish earlier diagnosis and improve the outcomes of treatment are essential to improve upon what is currently available," said the charity's director Helen Wilkinson.
"Early diagnosis of ectopic pregnancy is a key factor in improving treatment of the condition and helping to assure a woman's future fertility, therefore we welcome any advancement that could be made in this area including the University of Edinburgh's planned research into the possibility of a simple diagnostic test."