Can a scientific approach to induction of labor using hyoscine butyl bromide (HBB) concomitantly with prostaglandins shorten the duration of time to reach active stage of labor? A cohort study.

BACKGROUND

Hyoscine butyl bromide (HBB) is a muscarinic receptor antagonist, which inhibits the parasympathetic (cholinergic) activity of the utero-cervical plexus. It has been used to augment the progress of labor. Although, it cannot initiate uterine contractions, in combination with prostaglandins, it may shorten the duration of induction of labor due to its antimuscarinic action on the cervix, if it is administered according to the recently published scientific evidence.

OBJECTIVE

To determine the effect of hyoscine butyl bromide used concomitantly with prostaglandins on the time taken to reach 5 cm cervical dilatation in primigravidae.

MATERIAL AND

METHODS

This is a retrospective cohort study with 98 primigravidae receiving prostaglandins and HBB and 83 primigravidae receiving prostaglandins alone. HBB was administered using the hospital protocol based on the recently published scientific evidence (20 mg given as an infusion over 4 h) if there was no cervical change (dilatation and effacement) after 8 h of insertion of prostaglandin pessary. The time taken to reach 5 cm dilatation and the primary cesarean section rate were analyzed. The Mann-Whitney U Test & the Fisher's Exact Test were used for statistical analysis.

RESULTS

The median time to induction was 10 h (interquartile range [IQR]: 7-14, min: 2, max: 23) in women who received hyoscine butyl bromide compared with 19.5 h (IQR: 11.3-24, min: 4, max: 47) in women who did not (Mann-Whitney U Test p < 0.001). The primary cesarean section rate was 24.4% in the HBB group and 31.3% in the control group (Fisher's Exact Test, p > 0.136). There were no statistically significant differences in the gestational ages or birthweights between the two groups. There was no statistically significant difference in the Apgar scores, or adverse maternal and perinatal outcomes between the two groups.

CONCLUSION

Administration of 20 mg of hyoscine butyl bromide, diluted in 100 mL of normal saline administered intravenously over 4 h, based on the recently published scientific evidence, concomitantly with vaginal prostaglandins significantly shortened the time to reach 5 cm dilatation. In addition, it was associated with 8% statistically non-significant reduction in the rate of primary cesarean section.