Amniotic fluid prostaglandin concentrations increase before the onset of spontaneous labor at term

Abstract

Objectives. The role of prostaglandins (PGs) in the onset of human parturition has been controversial. Specifically, some investigators have proposed that PGs are the consequence rather than the cause of labor. An important question is whether or not amniotic fluid (AF) PG concentrations increase before the onset of labor in humans. Methods. The concentrations of PGs were determined in AF obtained from 167 singleton pregnant women with intact membranes. Patients were divided into four groups: (1) preterm not in labor (gestational age 15-36 weeks, n ¼ 65); (2) term not in labor (n ¼ 68); (3) spontaneous labor at term with cervical dilatation 54 cm (n ¼ 25); (4) spontaneous labor at term with cervical dilatation 4 cm (n ¼ 9). AF was obtained by transabdominal amniocentesis or collected at the time of cesarean delivery. All patients met the following criteria: (1) normal pregnancy outcome; (2) clear AF; (3) no significant medical or obstetric complications such as diabetes mellitus, preeclampsia, preterm birth, fetal growth restriction, or major congenital malformations; and (4) no significant neonatal complications. The concentrations of PGE2 and PGF2a in AF were determined by enzyme-linked immunosorbent assay (ELISA). Non-parametric analysis was performed. Results. (1) AF PG concentrations remained unchanged with advancing gestation until 36 weeks of gestation; (2) however, an abrupt increase in AF PG concentrations was observed before the onset of labor at term; (3) among cases without labor at term, the median AF PGF2a concentration increased with advancing gestation; (4) the presence of labor and the degree of cervical dilatation were significantly associated with a higher concentration of PGF2a.Conclusions. An abrupt increase in AF PG concentrations (25-fold for PGF2a) occurs before the onset of spontaneous labor at term in humans; these observations suggest that PGs increase prior to the onset of labor and contradict the claim that an increase in PG concentrations is the consequence of labor.

Growth perturbations in a phenotype with rapid fetal growth preceding preterm labor and term birth

“…The coincidence between these findings and the timing of the PTL episodes, at a median age of 32.5 gestational weeks (interquartile range, 29.2-34.6 weeks), implicates rapid fetal growth rates as contributory. This is a novel observation, provoking consideration of fetal contributions to the mechanisms and biological cascade underlying the onset of labor (Challis et al, 2002;Lee et al, 2008). Two findings emerged in this study that differentiated the growth patterns of these fetuses: (1) A three-phase growth phenotype characterized by two times of faster growth separated by an interval of slow-down in AC growth; (2) an abdominal growth perturbation that accompanied differences in proportionality and allometry.…”

An elevated amniotic fluid prostaglandin F2αconcentration is associated with intra-amniotic inflammation/infection, and clinical and histologic chorioamnionitis, as well as impending preterm delivery in patients with preterm labor and intact membranes

“…An elevated amniotic fluid PGF 2α concentration was defined as ≥170 pg/mL. This is based on our previous study which reported that an amniotic fluid PGF 2α concentration of 170 pg/mL corresponded to the value at the 95th percentile for pregnant women with intact membranes at 15–36 weeks of gestation who were not in labor [142]. …”

“…The main prostaglandins found in amniotic fluid are prostaglandin E 2 (PGE 2 ) and prostaglandin F 2α (PGF 2α ) [142, 178, 179]. The concentration of these eicosanoids increases prior to the onset of labor at term [136, 140, 142], during labor [133, 179] and rupture of the membranes [132], and in spontaneous preterm labor [particularly in the setting of microbial invasion of the amniotic cavity (MIAC)] [129–131, 137, 173, 180–187].…”

“…The main prostaglandins found in amniotic fluid are prostaglandin E 2 (PGE 2 ) and prostaglandin F 2α (PGF 2α ) [142, 178, 179]. The concentration of these eicosanoids increases prior to the onset of labor at term [136, 140, 142], during labor [133, 179] and rupture of the membranes [132], and in spontaneous preterm labor [particularly in the setting of microbial invasion of the amniotic cavity (MIAC)] [129–131, 137, 173, 180–187]. Despite the physiologic and pharmacologic importance of prostaglandins in spontaneous term and preterm labor, there is a paucity of literature examining the potential role of prostaglandin concentrations in the assessment of patients with preterm labor [129–131, 142, 173, 180–184, 187].…”

Altered Expression of Enzymes Regulating the Activity of Endothelin-1 in the Lower Segment of the Human Amnion During Labor1

“…The effects of proinflammatory cytokines and uterotonic agents known to be involved in the onset of labor were also examined in terms of the enzymes in human amniotic cells. TNFa, IL1b, and IL6 [13] as well as prostaglandin F2a (PGF2a) [14] are increased in amniotic fluid with labor at term, and they are increased in maternal serum before labor onset [15]. IL8 is induced by IL1b [16].…”