Pretreatment of the primigravid uterine cervix with mifepristone 30 h prior to termination of pregnancy: a double blind study.

OBJECTIVE

To determine the effect of the antiprogestogen mifepristone (RU 486) on cervical resistance before first trimester termination of pregnancy.

DESIGN

Prospective double blind randomized placebo controlled study.

SETTING

Department of gynaecology in a university teaching hospital, Sheffield.

SUBJECTS

80 Primigravid women greater than 18 years of age, undergoing termination of pregnancy at between 7 and 13 weeks gestation.

INTERVENTIONS

A single dose of 600 mg of mifepristone or placebo given orally 30 h before termination of pregnancy under general anaesthesia.

MAIN OUTCOME MEASURES

Cervical resistance to dilatation.

RESULTS

Pretreatment with mifepristone significantly reduced the amount of force required to dilate the cervix to 10 mm. In comparison with placebo, the mean sum of the peak forces obtained with dilators 4 to 10 mm was reduced from 84.3 N (SD 29.7) to 46.0 N (SD 26.7). Two women in the treated group had a cervical resistance of greater than 100 N compared with nine women in the placebo group (RR 0.18, 95% CI 0.04-0.89). The 8 mm dilator could be passed with less than 5 N force in 16 women (43%) in the treated group compared with none in the placebo group. Women in the active treatment group had more preoperative pelvic pain and vaginal bleeding but less postoperative pain.

CONCLUSION

Mifepristone significantly reduces cervical resistance in the first trimester of pregnancy and produces minimal side effects.