Could antiprogesterones be used as alternative cervical ripening agents?

We measured the effect of a progesterone antagonist on the pregnant cervix with a custom-built cervicometer. The change in cervical diameter was studied in 11 pregnant patients after oral administration of 600 mg of RU-486. In all cases RU-486 ripened the cervix (p = 0.0007). The average increase in diameter was 13% (95% confidence limits, 10% to 16%).