Factors associated with augmentation of labour with synthetic oxytocin: A cross-sectional study.

Background: While augmentation of labour with synthetic oxytocin is one of the most frequently performed childbirth interventions among women with spontaneous onset of labour, no prior research on this topic had been conducted in Ireland.

Aim: To identify the prevalence of and factors associated with augmentation of labour with synthetic oxytocin within the Irish context.

Methods: A cross-sectional study including data from 2,086 women who gave birth in one tertiary urban maternity hospital in Ireland in 2022 was conducted. Crude and adjusted odds ratios were calculated. Analyses examining the relationship between augmentation of labour with synthetic oxytocin and the mode of birth, childbirth interventions and adverse perinatal outcomes were stratified by cervical dilatation at the time when the synthetic oxytocin infusion was started.

Results: The overall prevalence of augmentation of labour with synthetic oxytocin was 18.70 %. At the time of starting the synthetic oxytocin infusion, 58.35 % of the women had a cervical dilatation of 0-4 cm. Nulliparity (OR 8.42, 95 % CI 6.48-10.96; p < 0.001) and private care (OR 1.67, 95 % CI 1.19-2.35; p = 0.004) significantly increased the odds of undergoing augmentation of labour with synthetic oxytocin. Augmentation of labour with synthetic oxytocin was associated with instrument-assisted birth for both women at 0-4 cm dilatation (aOR 2.38, 95 % CI 1.65-3.45; p < 0.001) and at ≥ 5 cm dilatation (aOR 2.76, 95 % CI 1.88-4.06; p < 0.001). Mixed associations were found with caesarean section, additional childbirth interventions and adverse perinatal outcomes, depending on the cervical dilatation at the time when the synthetic oxytocin infusion was started, with the exception of epidural analgesia that was significantly associated with augmentation of labour with synthetic oxytocin for both women at 0-4 cm dilatation (aOR 15.23, 95 % CI 9.84-23.57; p < 0.001) and those at ≥ 5 cm dilatation (aOR 12.37, 95 % CI 7.48-20.43; p < 0.001).

Conclusions: Due to its cross-sectional design, this study cannot establish causal relationships between augmentation of labour with synthetic oxytocin and the mode of birth, childbirth interventions or adverse perinatal outcomes. Nevertheless, considering its potential clinical implications, a reassessment of current Irish guidelines towards a more conservative stance to its use is warranted.