Prostaglandin release from human cervical tissue in the first trimester of pregnancy after preoperative dilatation with hygroscopic tents

Preoperative dilatation with hygroscopic tents before first trimester abortion by vacuum aspiration is widely accepted and reduces the risk of early and late complications. A softening effect and a reduced compliance to mechanical dilatation occurs in addition to pure mechanical dilatation of the cervix. If this softening is an effect of local prostaglandin release, however, is unknown. Prostaglandin (PG) release in vitro from cervical biopsies following dilatation in vivo by a synthetic hygroscopic tent (Dilapan) for periods of 4 h and 18 h was compared with that of biopsies from untreated women. No difference was observed between the release of PGE(2), PGF(2 alpha), or 6-keto-PGF(1 alpha). No significant difference was found in the tissue water content between treated and untreated women (83.8% versus 83.2%). Prostaglandins were also extracted from an alternative cervical dilator, Lamicel (a polyvinyl sponge impregnated with magnesium sulfate), and compared with the corresponding values from women pretreated with the cyclooxygenase inhibitor indomethacin before application of the tent. Significantly higher concentrations of PGE(2) and PGF(2 alpha) but not of 6-keto-PGF(1 alpha) were found in women who had not been indomethacin-treated compared with indomethacin-treated women. Slices of the cervix from non-pregnant women operated upon for benign conditions were divided into an outer stromal layer and an inner layer, including the mucosa, and the PG-release in vitro was measured. The inner layer of the cervix showed a significantly higher release of PGE(2) and PGF(2 alpha) compared with the outer layer. Lamicel treatment before first trimester abortion results in a significant dilatation of the cervix and a reduced compliance to mechanical dilatation, and this study supports the hypothesis that this effect is mediated via a local PG-release from the cervix. It seems reasonable to believe that Dilapan treatment too has the capacity to induce PG-release from the cervix, but this could not be demonstrated in this study, probably because needle biopsies taken mainly from the outer cervical layers were analyzed.