Researchers have identified a molecule that indicates ectopic pregnancy, a finding that could help doctors with early diagnosis and intervention.

Worldwide, ectopic pregnancy is a leading cause of pregnancy-related first trimester deaths. It's an abnormal pregnancy that occurs outside the uterus, usually occur in the Fallopian tube, cervix, ovaries or abdomen.

"Finding a simple and cost-effective test using biomarkers to diagnose ectopic pregnancies would have a significant impact on reducing emotional distress and unnecessary deaths," study researcher Andrew Horne, of the University of Edinburgh in the United Kingdom, said in a statement.

Researchers examined placental cell samples from 40 pregnant women , ages 18 to 45. They found levels of a molecule called placental growth factor (PGF) critical in forming the blood vessels of the placenta that nourish a growing fetus was lower in women who had ectopic pregnancies than women who had normal intrauterine pregnancies.

The discovery of the link between PGF levels and ectopic pregnancies will make it possible to make diagnoses quicker and earlier, when less invasive treatments can be used and risks to the pregnant woman are lower, Horne said.

Fewer than 50 percent of ectopic pregnancies are diagnosed during a patient's first visit to a doctor, according to the study. And even with improved ultrasound technology, that rate hasn't changed in 10 years.

Ectopic pregnancies are rare in the United States, but are more common in the developing world, where one woman dies for every 10 women who experience one, according to the study.

Women with ectopic pregnancies have extreme pelvic pain and often need a blood transfusion, Horne said, and "the inevitable multiple visits and tests that are currently necessary to diagnose ectopic pregnancies are a sizable expense for health services ."

Larger scale studies are needed before scientists can start testing for the molecule in a clinical setting, according to the study.

The study was published today (Nov. 4) in the Journal of Clinical Endocrinology & Metabolism.