GEMEPROST-INDUCED CERVICAL RIPENING - HISTOLOGICAL AND BIOPHYSICAL EFFECTS

The mechanism of prostaglandin-induced cervical ripening is not clear. The aim of this study was to measure the biophysical and histological effects of gemeprost on the cervix. Thirty-four women admitted for surgical termination of pregnancy in the first trimester were randomised in a double-blind manner to receive either gemeprost or placebo prior to surgery. In 20 (10 active, 10 placebo) a needle biopsy was taken from the anterior lip of the cervix prior to cervical dilatation for histology. The forces required to dilate the cervix from 3 mm to 10 mm were measured. A group of seventeen parous women undergoing surgical termination who did not receive gemeprost were also studied as a parous control group. A needle biopsy was obtained in eight of them and also in six non-pregnant parous women undergoing hysterectomy for benign conditions, the latter acting as a non-pregnant control group. Polymerised collagen was stained with Picrosirius red and glycosaminoglycans with alcian blue using a MgCl2 gradient. Optical densitometry was used as an objective measure of staining. Neutrophil concentration was assessed immunohistochemically. Gemeprost treatment increased free passibility (the size of the largest dilator which could be passed without encountering resistance) (P < 0.01), reduced the forces required to dilate the cervix (P < 0.01) reduced blood loss (P < 0.05), reduced the collagen concentration (P < 0.01) and was associated with a modest neutrophil influx (P < 0.02) as compared to placebo. The pregnant parous group had a significantly lower collagen concentration than the non-pregnant parous group (P < 0.02). The cervical glycosaminoglycan concentrations did not alter with gemeprost treatment or pregnancy, but the cervical concentration of chondroitin/dermatan sulphate was greater in the parous groups compared to the primigravid groups. Neither collagen concentration nor glycosaminoglycan concentration correlated with free passibility, total force or blood loss. These data show that gemeprost will reduce collagen concentration, but as there was no alteration in glycosaminoglycan concentration, it remains unclear whether this was related to collagenolysis or a subtle change in the ground substance investing the collagen fibrils.