Transfers of women planning birth in midwifery units: data from the birthplace prospective cohort study.

OBJECTIVE: To examine the percentage of women transferred, reasons for transfer and factors associated with the transfer of women planning birth in midwifery units (MUs). DESIGN: Prospective cohort study. SETTING: All freestanding midwifery units (FMUs) and alongside midwifery units (AMUs) in England. PARTICIPANTS: Twenty-nine thousand, two hundred and forty-eight eligible women with a singleton, term and 'booked' pregnancy, planning birth in an MU between April 2008 and April 2010. METHODS: Multivariable logistic regression was used to explore the sociodemographic and clinical characteristics associated with transfer. MAIN OUTCOME MEASURES: Transfer during labour or within 24 hours of birth. RESULTS: Over one in four women were transferred from AMUs and over one in five from FMUs. In both types of MU, compared with multiparous women aged 25-29 years, nulliparous women aged <20 years had higher odds of transfer (FMU-adjusted odds ratio [OR], 4.5; 95% confidence interval [CI], 3.10-6.57; AMU-adjusted OR, 2.6; 95% CI, 2.18-2.06), and the odds of transfer increased with increasing age. Nulliparous women aged ≥ 35 years in FMUs had 7.4 times the odds of transfer (95% CI, 5.43-10.10) and, in AMUs, 6.0 times the odds of transfer (95% CI, 4.81-7.41). Starting labour care after 40 weeks of gestation and the presence of complicating conditions at the start of labour care were also independently associated with a higher risk of transfer. CONCLUSIONS: Transfer from MUs is common, especially for first-time mothers. This study provides evidence on the maternal characteristics associated with an increased risk of transfer, which can be used to inform women's choices about place of birth.