Retrospective study of maternal and neonatal outcomes after induction compared to spontaneous start of labour in women with one previous birth in uncomplicated pregnancies ≥ 41+3.

OBJECTIVES

To study the association between induction and outcome among two-parous women in uncomplicated pregnancies ≥ 41+3, stratified by first labour delivery mode and conditions present at first delivery.

METHODS

The Swedish Medical Birth Register was used to identify 58,964 uncomplicated singleton pregnancies among women with one previous birth between 1998 and 2014. Women with any registered pregnancy complications were excluded to minimise the risk for indication bias. The outcomes considered were emergency caesarean section (CS), and poor neonatal outcome (Apgar score <7 at 5 min, neonatal death, or meconium aspiration).

RESULTS

Women who were induced at their second labour had higher emergency CS rates compared to women in spontaneously started deliveries (adjusted risk ratio, ARR: 2.11; 95% CI: 2.00-2.23). Low Apgar score was more common after induction compared to spontaneously started labours (1.0 vs. 0.7%) (ARR: 1.44; 95% CI: 1.18-1.77). Increased CS rates were also found when comparing induction at 41 + 3 to 41 + 6 weeks to labour at 42 weeks or more, regardless of labour start (ARR 1.39; 95% CI: 1.26-1.52).

CONCLUSIONS

We found an increased risk of CS and poor neonatal outcome after second labour induction in prolonged pregnancies. The second labour vaginal success rate after induction was highly dependent, on first labour delivery mode, but also on diagnoses and conditions present at the first delivery.