Saliva test reveals early birth risk

An exploratory study led by Professor Lucilla Poston of King’s College London has shown that women going into early pre-term labour have low levels of progesterone in their saliva as early as 24 weeks of gestation, and that these levels fail to rise during pregnancy in the normal way.

This offers the possibility of developing a simple, non-invasive test to identify women at increased risk of delivering early.

 Progesterone is a hormone that helps regulate the menstrual cycle and is the primary hormone of pregnancy. It is produced in large amounts from the placenta and acts to stop the womb from contracting.

The research teams at King’s College London and University College London collected specimens of saliva from women taking part in an existing randomised control trial of preventive treatment for pre-term birth. Women recruited to the study all had an increased risk of having a pre-term birth.

Saliva samples were taken from these women every week from 24 weeks of gestation until 34 weeks or delivery (whichever was the sooner), and analysed.  

The results published in BJOG: An International Journal of Obstetrics and Gynaecology, show that the concentration of progesterone in the saliva of women delivering after spontaneous labour before 34 weeks was significantly lower than those giving birth at term (after 37 weeks) at all gestational ages from 24 weeks onwards.

The authors note that progesterone is known for its anti-inflammatory properties, and suggest that low levels of the hormone in the maternal body could contribute to bacterial infection, a recognised cause of early pre-term labour. Based on their findings, researchers believe saliva progesterone could be a useful predictor of early preterm labour and delivery. 


Professor Poston said, ‘This very interesting study, funded by Tommy’s, backs up previous research which hinted at the importance of low saliva progesterone as a marker for labour onset.

‘We are now planning a much larger study to validate these preliminary findings. Saliva is easy to collect, there is no need for a needle or a blood sample and it would be wonderful if in the future we only had to ask a pregnant woman to produce a small sample of saliva to know whether or not she was at risk of very early premature birth.’