Longitudinal Ultrasound Evaluation of Dilapan-S During Cervical Ripening

To assess the diameter change of hygroscopic rod dilation during 12 hours of cervical ripening.

This was an observational, prospective study of term women undergoing labor induction with a bishop score ≤ 6. Women were allocated into two groups (soaked gauze or no gauze) stratified by parity. Using transvaginal ultrasound, maximal rod diameters were obtained in a longitudinal plane. Measurements were taken at four pre-specified time points (3, 6, 8, and 12 hours). All rods were removed at 12 hours from insertion. Patient satisfaction scores between the groups were assessed. To evaluate if measures were significantly different among the four time points, a generalized linear model was used. Independent t-tests were used to compare mean rod diameter values and pain measures between the two groups. Fisher Exact tests were used to evaluate categorical satisfaction measures.

Forty-four women were recruited with a total of 178 hygroscopic rods placed. Mean rod diameters (mm) were significantly different among the four time periods (3 hour: 7.9 mm [SD 0.9]; 6 hour: 9.4 mm [SD 0.9]; 8 hour: 10.0 mm [SD 0.9]; 12 hour: 10.9 mm [SD 0.8]; P-value <.001). After stratifying by the use of gauze, there was no difference in rod diameters at 3, 6, 8, and 12 hours respectively. There was no difference in patient satisfaction scores between the two groups.

The majority of hygroscopic rod dilation occurs within the first 8 hours of cervical ripening. Placement of saturated gauze does not accelerate rod dilation.