Pregnant woman speaking with doctor

How effective is progesterone for preventing preterm birth?

Preterm birth can be dangerous for newborns and their mothers, and not all preterm births are alike – the earlier they are, the greater the risk. This is why medications and treatment designed to avoid preterm birth aim to prolong pregnancy until as close to full term as possible, whether that means adding three days to the length of a pregnancy, or three weeks.

Who might progesterone be a good fit for?

Studies show that weekly progesterone treatments may help reduce the risk of preterm birth for those who have certain risk factors, like a short cervix.

What about if you have a history of preterm birth?

Those who have had spontaneous preterm deliveries of single babies in the past are especially at risk for preterm delivery. Some research suggested that progesterone treatment was helpful for those with a history of prior preterm birth, and that getting weekly progesterone injections would lower the risk of preterm labor. However, the PROLONG study published in 2020 found that weekly progesterone injections did not have a significant benefit for those with a history of preterm birth.

Because the evidence is mixed for those with a history of preterm birth, talk through the possible benefits and risks of progesterone treatment with your healthcare provider.

How does it work?

Progesterone works by preventing the contractions that kickstart labor. This means that even in cases where progesterone treatments don’t prevent preterm labor, they may delay labor significantly, giving babies longer to develop in the womb. Babies who are considered to be “late preterm” – babies born between 34 and 36 weeks gestation – have a lower risk of more dangerous health complications, and the closer to term a pregnancy gets, the better the odds are.

Progesterone isn’t an effective treatment for those carrying twins or multiples, and may not be right for those who have personal histories of certain health conditions. If you’re concerned about your risk for preterm labor, talk to your provider about possible prevention strategies.

Learn more about preterm labor

  • Vincenzo Berghella. “Cervical insufficiency.” UpToDate. Wolters Kluwer, December 5 2017. Retrieved December 19 2017.
  • Mary L. Gavin. “When do pregnant women need progesterone shots?” KidsHealth. The Nemours Foundation, November 2016. Retrieved December 19 2017.
  • S.S. Hassan. “Vaginal progesterone reduces the rate of preterm birth in women with sonographical short cervix: a multicenter, randomized, double-blind, placebo-controlled trial.” Ultrasound in Obstetrics and Gynecology. 38(1): 18-31. July 2011. Retrieved December 20 2017.
  • Paul J. Meis, et al. “Prevention of Recurrent Preterm Delivery by 17 Alpha Hydroxyprogesterone Caproate.” New England Journal of Medicine. 2003; 348:2379-2385. June 12 2003. Retrieved December 20 2017.
  • M.S. To, J. Miletin, J. Semberova, S. Daly. “Is routine tranvaginal cervical length measurement cost-effective in a population where the risk of spontaneous preterm birth is low?” Acta Obstetrica Gynecologica Scandinavica. 95(12): December 2016. Retrieved December 19 2017.
  • “Preterm birth fact sheet.” World Health Organization. World Health Organization, November 2017. Retrieved December 20 2017.
  • “Progesterone treatment to help prevent preterm birth.” March of Dimes. March of Dimes, August 2014. Retrieved December 19 2017.
  • M.S. To, et al. “Cervical assessment at the routine 23-week scan: standardizing techniques.” Ultrasound in Obstetrics & Gynecology. 17(3): 217-9. March 2001. Retrieved December 19 2017.
  • Cerner Multum. “Progesterone vaginal.” University of Michigan. Regents of the University of Michigan, March 13 2015. Retrieved December 19 2017.

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