Early Versus Delayed Oxytocin Infusion Following Amniotomy in Nulliparous Women

This was a randomised controlled trial undertaken in the labour room of UKMMC for a period of eighteen months from August 2014 until February 2016. Eligible women who were admitted in spontaneous labour or for induction of labour were recruited. For women who underwent induction of labour, an interval of at least six hours following vaginal prostaglandin before recruitment was mandatory to avoid overlapping effect of prostaglandin and oxytocin. Upon enrolment, each patient was given a study explanation and written consent was obtained.

The randomisation sequence, either to the early oxytocin group or the delayed oxytocin group, was generated using the computer randomisation program in block of two. Allocation to either arm of treatment was determined by the sequential opening of sealed numbered envelopes.

In the first arm of early oxytocin group, labour augmentation with oxytocin was started early following artificial ruptured of membrane(ARM). In the second arm of delayed oxytocin group, oxytocin augmentation was delayed at two hours after ARM and this practice is currently being used as standard protocol in this hospital to manage women in labour. In both arms,the infusion rate was doubled every 30 minutes to a maximum of 48 mL/h or until four to five moderate contractions per 10 minutes were achieved at which point the infusion rate was maintained. Continuous fetal heart rate monitoring was maintained throughout the intrapartum period. Vaginal examination was performed at four hours after ARM as well as when clinically indicated ie. abnormal cardiotocography (CTG) and maternal desire to bear down. In the presence of abnormal CTG, either fetal blood sampling or expedited delivery was undertaken as per decided by the obstetrician in charge.

Inclusion criteria

• gestational age between 36+0 to 41+6 weeks
• singleton pregnancies in cephalic presentation
• estimated fetal weight between 2.5 - 4.0 kg
• cervical dilatation of 4 cm with intact membranes
• normal fetal heart rate trace before artificial rupture of membranes

Exclusion criteria

• Women with significant medical (eg. heart disease, pre-eclampsia, diabetes with high dose insulin, retroviral disease)
• fetal abnormality (eg. fetal growth restriction or small for gestational age < 2.5 kg, suspected macrosomia > 4.0 kg, fetal anomaly)