Planned births in freestanding and alongside midwifery units: do women have fewer interventions in freestanding units?

Background For ‘low risk’ women, there is good evidence that planned birth in a midwifery unit is safe for the baby and is associated with a reduced chance of maternal interventions compared with birth planned in an... [ view full abstract ]

Background

For ‘low risk’ women, there is good evidence that planned birth in a midwifery unit is safe for the baby and is associated with a reduced chance of maternal interventions compared with birth planned in an obstetric unit. The Birthplace study findings additionally suggest a possible difference in intervention rates in births planned in freestanding midwifery units (FMU) compared with births planned in alongside midwifery units (AMU), but these differences have never been robustly evaluated.

Methods

We used data on ‘low risk’ women with singleton, term, ‘booked’ pregnancies collected in the Birthplace national prospective cohort study to compare interventions and outcomes by parity in 11,265 planned FMU births and 16,673 planned AMU births. We used logistic regression to adjust for potential confounders, and used planned AMU birth as the reference group. Outcomes considered included adverse perinatal outcome (Birthplace primary outcome measure) and a range of maternal interventions and outcomes. We used a significance level of 5% for the Birthplace primary outcome and 1% for all secondary outcomes.

Results

There was no significant difference in adverse perinatal outcomes between planned AMU and FMU births. The odds of instrumental delivery were significantly reduced in planned FMU births in both nulliparous (10.8% vs. 16.3%) and multiparous women (1.1% vs 2.5%) and the odds of having a ‘straightforward vaginal birth’ were significantly increased in planned FMU births compared with planned AMU births (nulliparous: 78.8% vs 71.5%; multiparous: 97.0% vs 94.6%). The odds of intrapartum caesarean section did not differ significantly between the two settings (nulliparous: 6.7% vs 7.7%; multiparous: 0.7% vs 1.0%). The odds of augmentation and episiotomy were significantly reduced in planned FMU births.

Conclusion

Our findings confirm that ‘low risk’ women who planned birth in an FMU had lower rates of instrumental delivery and higher rates of straightforward vaginal birth compared with women who planned birth in an AMU; and that outcomes for babies do not appear to differ between these two settings. Generally the findings suggest a trend towards lower intervention rates and fewer adverse maternal outcomes in planned FMU births compared with planned AMU births.