Labour dystocia--risk of recurrence and instrumental delivery in following labour--a population-based cohort study.

OBJECTIVE: To investigate risk of recurrence of labour dystocia and mode of delivery in second labour after taking first labour and fetal and maternal characteristics into account.
DESIGN: A population-based cohort study.
SETTING: The Swedish Medical Birth Register from 1992 to 2006. POPULATION: A total of 239 953 women who gave birth to their first and second singleton infants in cephalic presentation at ≥ 37 weeks of gestation with spontaneous onset of labour.
METHODS: We used logistic regression analysis to estimate crude and adjusted odds ratios. MAIN OUTCOME MEASURES: Labour dystocia and mode of delivery in second labour.
RESULTS: Overall labour dystocia affected only 12% of women with previous dystocia. Regardless of mode of first delivery, rates of dystocia in the second labour were higher in women with than without previous dystocia, but were more pronounced in women with previous caesarean section (34%). Analyses with risk score groups for dystocia (risk factors were long interpregnancy interval, maternal age ≥ 35 years, obesity, short maternal stature, not cohabiting and post-term pregnancy) showed that risk of instrumental delivery in second labour increased with previous dystocia and increasing risk score. Among women with trial of labour after caesarean section with previous dystocia and a risk score of 3 or more, 66% had a vaginal instrumental or caesarean delivery (17 and 49%, respectively). In women with trial of labour after caesarean section without previous dystocia and a risk score of 0, corresponding risk was 32% (14 and 18%, respectively).
CONCLUSION: Previous labour dystocia increases the risk of dystocia in subsequent delivery. Taking first labour and fetal and maternal characteristics into account is important in the risk assessments for dystocia and instrumental delivery in second labour.