The use of progestational agents for preterm birth: lessons from a mouse model

On the basis of the recent Maternal Fetal Medicine Unit Networks clinical trial, the American College of Obstetricians and Gynecologists supports the administration of 17-alpha hydroxyprogesterone caproate to high-risk patients. Because inflammation/infection is believed to be a contributing factor in many cases of preterm birth, it is imperative to understand the effect of 17-alpha hydroxyprogesterone caproate treatment in this clinical situation.

Using a mouse model of localized intrauterine inflammation, we investigated the ability of progestational agents to prevent preterm birth. On gestational day 15 (E15), dams were assigned randomly to treatment with 17-alpha hydroxyprogesterone caproate, medroxyprogesterone acetate, or vehicle before intrauterine infusion of lipopolysaccharide. All dams were monitored for morbidity and preterm birth. Three separate sets of experiments were performed to assess different outcomes at 6, 24, and 96 hours. At 6 and 24 hours, C-reactive protein, interleukin-6, and interleukin-10 levels were measured in maternal serum by enzyme-linked immunosorbent assay.

Pretreatment with 17-alpha hydroxyprogesterone caproate or medroxyprogesterone acetate before intrauterine lipopolysaccharide treatment significantly decreased the preterm birth rate, compared with lipopolysaccharide treatment alone. Medroxyprogesterone acetate treatment was more effective than 17-alpha hydroxyprogesterone caproate treatment in the prevention of preterm birth and resulted in live pups at term. Treatment with 17-alpha hydroxyprogesterone caproate was associated with significant maternal morbidity.

In the setting of intrauterine inflammation, progestational agents decrease the preterm birth rate but can result in maternal morbidity. 17-Alpha hydroxyprogesterone caproate should not be used in patients who are suspected of having subclinical infection and/or acute preterm labor. The mechanisms by which progestational agents inhibit preterm birth warrants further investigations so that the use of this drug to appropriate populations could be pursued without undue fetal or maternal harm.