[Mifepristone for induction of labor]

Abstract

Objectives: To evaluate the effectiveness of mifepristone administered prior to labor induction, and to study its safety for mother and fetus.

Methods: 124 nullipara, 37-42 gestational weeks, with indications for labor induction were recruited, and randomly allocated into 2 groups. Group A (n = 62) was given mifepristone 50 mg q.12.h. for 2 days, followed by PG05 or oxytocin, while group B (n = 62) was were observed for 2 days before labor induction by PG05 or oxytocin. Blood samples were obtained for determination of mifepristone concentration and hormone levels including estradiol, progesterone, testosterone, cortisol, aldosterone and human placental prolactin at recruitment and immediately after delivery, and umbilical cord blood was collected at the same time.

Results: Cervical Bishop score increased significantly in the mifepristone pretreatment group when compared with the control group. 22.58% of the women underwent spontaneous delivery after mifepristone treatment and 4.84% of the controls followed suit (P < 0.01). The oxytocin dose required was significantly less in group A, but the success rate was higher (P < 0.05). Side-effects associated with mifepristone was mild. Maternal serum mifepristone peak levels ranged from 200 to 700 micrograms/L, with t1/2 of 21.7 hr. The concentration of mifepristone in umbilical blood was low and stable. The ratio of umbilical/maternal mifepristone level was 0.25 +/- 0.08. Determination of hormone profiles did not show any significant difference between the 2 groups.

Conclusions: Mifepristone is an effective inductive agent for cervical ripening and initiation of labor in term pregnancy, and can improve the outcome of labor induction.