Medroxyprogesterone acetate, but not progesterone, protects against inflammation-induced parturition and intrauterine fetal demise

Objective: This study was undertaken to determine whether progestational agents can prevent inflammation-induced preterm parturition and fetal demise. Study design: The activation of contractile and inflammatory pathways in response to localized intrauterine inflammation was investigated by using quantitative polymerase chain reaction (PCR). Serum progesterone (P4) levels and alterations in progesterone receptor-B (PR-B) were determined with radioimmunoassay and quantitative PCR, respectively. With our in vivo model of intrauterine inflammation, animals were randomly assigned to pretreatment with P4 or medroxyprogesterone acetate (MPA) before intrauterine lipopolysaccharide (LPS). Animals were observed for preterm delivery. The number of live pups 48 hours after intrauterine LPS was recorded for each treatment group. The ability of MPA to alter signal transduction pathways leading to preterm parturition were investigated by quantitative PCR and histochemical studies. Results: Intrauterine inflammation is associated with decreased serum progesterone levels and decreased transcription of PR-B. Preterm delivery rates were 100% for LPS alone, 63% for LPS + P4, and 0% for LPS + MPA. No live pups remained at 48 hours in the LPS or LPS + P4 groups. Pretreatment with MPA significantly preserved fetal viability. MPA suppressed activation of contraction-associated genes and inflammatory mediators and prevented cervical ripening in response to intrauterine inflammation. Conclusion: MPA, with its progestational and anti-inflammatory properties, prevented inflammation-induced preterm parturition and significantly preserved fetal viability. (C) 2004 Elsevier. Inc. All rights reserved.