Women at risk for a preterm birth are often given progesterone by injection or vaginal suppository. Progesterone helps quiet the muscular contractions of the uterus that signal the onset of labor. A drop in progesterone levels is one of the hormonal signals that begins labor.

Now researchers in the U.K. propose using saliva testing to determine whether pregnant women need progesterone to avoid preterm delivery. According to a study in the British Journal of Obstetrics and Gynaecology, more than 50,000 babies are born prematurely in the U.K. every year, at an enormous cost to the British medical system.

Researchers used saliva testing to measure progesterone levels in 92 pregnant women who were at risk of a preterm delivery. They found that women who delivered before 34 weeks had significantly lower progesterone levels than those who delivered after 37 weeks.

According to a BBC news report, the study’s lead author, “Professor Lucilla Poston, from the Maternal and Foetal Research Unit at King's College London, said they were 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.’”

A number of past studies have shown that giving progesterone to women at risk can reduce early delivery by 20 to 30 percent.

References

da Fonseca EB, Bittar RE, Carvalho MHB et al, “Prophylactic administration of progesterone by vaginal suppository to reduce the incidence of spontaneous preterm birth in women at increased risk: A randomized placebo-controlled double-blind study,” American Journal of Obstetrics & Gynecology. 188(2):419-424, February 2003.

Dodd JM, Flenady V, Cincotta R, Crowther CA, “Prenatal administration of progesterone for preventing preterm birth,” Cochrane Database Syst Rev 2006 Jan 25;(1).

Lachelin GCL, McGarrigle HHG, Seed PT et al, “Low saliva progesterone concentrations are associated with spontaneous early preterm labour (before 34 weeks of gestation) in women at increased risk of preterm delivery,” British Journal of Obstetrics & Gynaecology vol 116:11 pp 1515 – 1519 Published Online: 22 Jul 2009.