Researchers say that a single test that detects levels of the hormone progesterone along with other diagnostic tools is a better way of determining whether the pregnancy will be successful or end in a miscarriage. 

About a third of all would-be-mothers experience vaginal bleeding or pain during the first trimester which can be a sign of pregnancy complications.

Currently, doctors use ultrasound to determine whether or not the pregnancy is viable but an ultrasound could be inconclusive. Using progesterone tests as a tool for detecting an unviable pregnancy was proposed but there wasn't enough evidence that the test would work.

Progesterone is a hormone that is mainly produced in the ovaries which gets the body ready for a pregnancy. The serum progesterone test is used to determine the levels of the hormone in the blood. The test is conducted to find out if the woman is ovulating and to determine the risk of miscarriage. The test is also used to evaluate a woman with repeated miscarriages, although other tests are usually conducted for this purpose.

In the present study, researchers from the UK and Denmark tried to find out the accuracy of these tests in determining the viability of a pregnancy. The researchers analyzed past studies conducted on these tests. A total of 26 studies involving 9,436 pregnant women were chosen for the analysis. A single low progesterone measurement was able to indicate a non-viable pregnancy, especially when the ultrasound reports were inconclusive.

However, the test's accuracy was low when the doctor hadn't performed an ultrasound. Researchers say that "the test should be complemented by another test to increase its diagnostic accuracy" because low progesterone levels can occur even in viable pregnancies.

"This test is highly accurate when complemented by ultrasound and could be added to the existing algorithms for the evaluation of women with pain or bleeding in early pregnancy as it can accelerate diagnosis, researchers added.

The study was published in the journal BMJ.