THE RELATIONSHIP BETWEEN SPONTANEOUS RUPTURE OF MEMBRANES, LABOR, ANDMICROBIAL INVASION OF THE AMNIOTIC CAVITY AND AMNIOTIC-FLUID CONCENTRATIONS OF PROSTAGLANDINS AND THROMBOXANE-B(2) IN TERM PREGNANCY

OBJECTIVE: The purpose of this study was to examine the relationship b etween rupture of membranes, labor, and microbial invasion of the amni otic cavity and amniotic fluid concentrations of eicosanoids in patien ts with spontaneous rupture of membranes at term. STUDY DESIGN: Amniot ic fluid was retrieved by transabdominal amniocentesis from patients w ith rupture of membranes and patients with intact membranes at term. S tudies to determine the microbial state of the amniotic cavity include d culture for bacteria and mycoplasmas, Gram stain, amniotic fluid whi te blood cell count, and Limulus amebocyte lysate. Eicosanoids (prosta glandin E2, prostaglandin F2alpha and its stable metabolite, 6-keto-pr ostaglandin F1alpha, and thromboxane B2) were determined with sensitiv e and specific radioimmunoassays validated for human amniotic fluid. S tatistical inference was conducted with analysis of variance and linea r contrast. RESULTS: (1) Spontaneous rupture of membranes at term was associated with a significant increase in amniotic fluid concentration s of all eicosanoids measured in this study except 6-keto-prostaglandi n F1alpha. (2) Early labor in patients with rupture of membranes was a ssociated with a significant increase in the amniotic fluid concentrat ion of all eicosanoids. (3) A significant increase in amniotic fluid e icosanoids in women with microbial invasion of the amniotic cavity cou ld not be documented. CONCLUSIONS: Whereas preterm labor in the absenc e of microbial invasion of the amniotic cavity is not associated with a significant increase in amniotic fluid concentrations of prostagland ins, a clear increase was documented in women with early labor after s pontaneous rupture of membranes. These observations suggest that there are fundamental differences in the biochemistry of term and preterm p arturition.