Context: 9,11-Prostaglandin F₂ (9,11-PGF₂) can contract uterine smooth muscle with a potency equal to PGF₂. Its presence in the human uterus and production by human gestational tissues is unknown.

Objective: These studies were performed to determine whether the PGD₂-derived 9,11-PGF₂ is both present in human amniotic fluid and synthesized by human gestational tissues and if so, whether labor-related substances could regulate its production.

Results: Detectable concentrations of 9,11-PGF₂ were found in amniotic fluid samples and appeared to increase in late gestation. All gestational tissues studied synthesized 9,11-PGF₂ with the placenta having the highest basal production rate followed by the amnion and then the choriodecidua. Interleukin-1 (IL-1) and tumor necrosis factor- (TNF-) caused concentration-dependent increases in 9,11-PGF₂ production in human amnion and choriodecidual explants. Moreover treatment of choriodecidual and placental explants with lipopolysaccharide (LPS) resulted in a significant increase in 9,11-PGF₂ production rates reaching a maximum of 13-fold in the choriodecidua. Studies examing the effects of the addition of exogenous PGD₂ strongly indicated that the choriodecidua has significant ability to convert PGD₂ to 9,11-PGF₂, while the amnion has little.

Conclusions: These results demonstrate for the first time that 9,11-PGF₂ is present in human amniotic fluid and that it is produced by human gestational tissues and upregulated by bacterial cell wall components and pro-inflammatory cytokines. We suggest that this prostaglandin may play a part in the mechanisms of human labor at term and preterm.