Progesterone’s Important Role in Preventing Preterm Birth

There are over 500,000 premature babies born in the United States every year and a high percentage of these infants will experience birth defects as a result of this. The preterm birth rate (defined as birth prior to 37 weeks of gestation) has declined slightly over the past 3 years, but in the United States is still close to 12%. Preterm babies are much more likely to be low birth weight and studies indicate that children who are born preterm score lower on intelligence tests, are more susceptible to depression and have an increased rate of cerebral palsy, vision or hearing loss and respiratory distress syndrome.

There are many causes of preterm labor including uterine infection, multiple pregnancies and hormone fluctuations. One of the primary treatments for women who are at risk for preterm delivery is progesterone. Just as progesterone in the first trimester can reduce the incidence of early termination of pregnancy, progesterone during the later trimesters can reduce the rate of preterm deliveries. Progesterone relaxes the uterine muscle, helps to maintain cervical length and has some anti-inflammatory properties. One study by the NIH found that a vaginal progesterone gel could reduce the rate of premature delivery in high-risk women by 45%.

Fetal adrenal production in the third trimester contributes to a natural increase in 17-hydoxyprogesterone, a metabolite of progesterone. The caproic acid form of this hormone has been used in injectable form since the 1950s to prevent preterm delivery and is commonly referred to as 17-P. 17-P was first marketed under the name Delautin® and was FDA approved in 1956. In 1999 the manufacturers pulled the drug from the market and for the past decade or so 17-hydroxyprogesterone caproate has only been available through compounding pharmacies at a cost of approximately $30/month to the patient. This all changed in February 2011 when a "new" brand name of the hormone was FDA approved. This new brand, Makena®, debuted at a cost of $1,500/dose or $6,000/month. At this price, a typical 20 week course of Makena would cost $30,000 compared to the few hundred for the compounded version of the same molecule. The problem is that the manufacturer has exclusive rights to make 17-P for the next seven years and have warned some pharmacies that they could risk FDA enforcement if they continued to compound the drug. Physicians who use this therapy, as well as compounding pharmacies, have been actively protesting the exorbitant prices of the brand name 17-P, and since February the makers of Makena have lowered the price by half. The FDA has stated that it would not attempt to prosecute compounding pharmacies who supply the generic hormone unless there were safety concerns.

What does this have to do with salivary testing you ask? Understanding the important role that progesterone plays in maintaining pregnancy throughout the entire gestation is imperative to all practitioners treating reproductive age women. If a woman has low levels of progesterone during the luteal phase before she is pregnant, this may indicate an increased need for progesterone supplementation during pregnancy. Studies that are performed on brand name medications can provide us with valuable data that can be extrapolated to support general progesterone therapy to support these specific conditions.


  1. Hassan SS et al. Vaginal progesterone reduces the rate of preterm birth in women with a sonographic short cervix: a multicenter, randomized, double-blind, placebo-controlled trial. Ultrasound Obstet Gynecol. 2011 Apr 6.
  2. Simhan HN, Caritis SN (2007). Prevention of Preterm DeliveryNew England Journal of Medicine 357 (5): 477-487.
  3. Dodd JM, Flenady V, Cincotta R, Crowther CA (2006). Prenatal administration of progesterone for preventing preterm birth.Cochrane Database Systematic Reviews
  4. Gretchen Cuda-Kroen. Price of Premature - Birth Drug Criticized. April 13, 2011 NPR
  5. http://www.columbialabs.com/Collateral/Documents/English-US/Prochieve%20PI%20v06.pdf
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The Canary Club is an educational advisory group with a team of medical advisors headed by Richard Shames, M.D.