Introduction

Induction of labour is a common obstetric intervention and choice of pharmacologic agent can significantly impact labour outcomes. Vaginal misoprostol and dinoprostone are widely used for cervical ripening and induction, yet their comparative effectiveness across different gestational ages remains understudied.

Aim

To compare the length of labour and associated delivery outcomes between vaginal misoprostol and dinoprostone used for induction of labour across various gestational ages.

Patient Profile

• N=3774 singleton pregnancies
• Patients only included if they began their induction with either vaginal misoprostol 25mcg that can be redosed every 4 h or vaginal dinoprostone 10mg insert (maximum of 12 h) for induction of labour

Methods

• Retrospective cohort study from 2009 to 2019
• Pregnancies were categorised by gestational age at induction:
  • Preterm (34w0d–36w6d), n=289 (7.6%)
  • Term (37w0d–40w6d), n=2509 (66.0%)
  • Late term (≥41w0d), n=1002 (26.4%)
• Assess real-world effectiveness and outcomes

Study endpoints

Primary outcome: Time to insertion of medication to time to vaginal delivery

Secondary outcomes: Length of first and second stages of labour, length of rupture of membranes, mode of delivery, neonatal Apgar scores at 1 and 5 min and neonatal intensive care unit admission

Results

Labour Duration

• Misoprostol resulted in shorter labour compared to dinoprostone across all gestational age groups

Table 1: Comparison of Labour Duration Across All Gestational Ages

Stages of Labour

• First Stage of Labour: Shorter with misoprostol across all gestational ages

Table 2: Comparison of First Stage of Labour Duration Across Gestational Ages

• Second Stage of Labour: Shorter with misoprostol at term and late term

Table 3: Comparison of Second Stage of Labour Duration Across Gestational Ages

• After adjusting for confounders (race, ethnicity, gravidity, nulliparity and chronic hypertension),
  • Largest difference in length of labour was at preterm: 41% increase associated with dinoprostone
  • Smallest difference was in late term gestation: 27% increase with dinoprostone
  • First stage of labour longer with dinoprostone across all gestational ages

(preterm IRR: 1.40, p < 0.01; term IRR: 1.41; p < 0.01, late term IRR: 1.28; p < 0.01)

• Second stage of labour longer with dinoprostone across all gestational ages

(preterm IRR: 1.50; p < 0.01, term IRR: 1.15; p < 0.01, late term IRR: 1.29; p < 0.01)

Caesarean Section Risk:

At term, dinoprostone was associated with higher odds of caesarean delivery compared to misoprostone (OR 1.34)

Neonatal Outcomes:

No significant differences were found in 1- and 5- minute Apgar scores or NICU admissions between the two groups

Conclusion

• Vaginal misoprostol was associated with shorter labour course across all gestational ages. It was also associated with shorter times across all stages of labour.
• Dinoprostone vaginal insert at term had an increased risk of caesarean section.

Reference

Reproductive, Female and Child Health. 2022;1:62–68.