Association between configuration, unit characteristics and adjusted intervention rates in low-risk women in OUs
| Unit or configuration characteristic (number of OUs) | Nulliparous women | Multiparous women | ||||
|---|---|---|---|---|---|---|
| Outcome measure | R2 (%)* | Coefficient† | p Value | R2 (%)* | Coefficient† | p Value |
| Size‡ (n=35) | ||||||
| Straightforward birth | 0.1 | −0.01 | 0.88 | 8.8 | 0.08 | 0.05 |
| Normal birth | 1.0 | −0.05 | 0.64 | 4.4 | 0.09 | 0.18 |
| Intrapartum caesarean section | 5.8 | −0.08 | 0.05 | 10.6 | −0.07 | 0.01 |
| Instrumental delivery | 5.0 | 0.09 | 0.33 | 2.3 | −0.03 | 0.53 |
| Number of delivery beds§ (n=36) | ||||||
| Straightforward birth | 1.6 | −0.23 | 0.50 | 1.2 | 0.14 | 0.61 |
| Normal birth | 6.3 | −0.63 | 0.12 | 0.1 | 0.06 | 0.90 |
| Intrapartum caesarean section | 0.0 | 0.03 | 0.94 | 0.0 | −0.02 | 0.96 |
| Instrumental delivery | 1.8 | 0.25 | 0.53 | 2.3 | −0.13 | 0.44 |
| Percentage of midwifery (‘under’) staffing¶ (n=30) | ||||||
| Straightforward birth | 3.5 | 0.06 | 0.31 | 15.1 | 0.08 | 0.01 |
| Normal birth | 0.1 | −0.01 | 0.89 | 1.7 | 0.05 | 0.48 |
| Intrapartum caesarean section | 17.6 | −0.10 | 0.03 | 12.6 | −0.05 | 0.11 |
| Instrumental delivery | 0.2 | 0.02 | 0.80 | 5.6 | −0.04 | 0.07 |
| Presence of AMU** (n=35) | ||||||
| Straightforward birth | 1.4 | −1.40 | 0.55 | 14.8 | −3.14 | 0.04 |
| Normal birth | 10.1 | −5.16 | 0.08 | 21.1 | −6.35 | 0.02 |
| Intrapartum caesarean section | 22.8 | 4.99 | 0.03 | 23.1 | 3.23 | 0.06 |
| Instrumental delivery | 3.8 | −2.40 | 0.34 | 0.0 | 0.09 | 0.92 |
| Percentage of planned non-OU births†† (n=30) | ||||||
| Straightforward birth | 8.2 | −0.17 | 0.06 | 26.3 | −0.22 | 0.01 |
| Normal birth | 6.1 | −0.20 | 0.08 | 17.4 | −0.25 | 0.01 |
| Intrapartum caesarean section | 31.8 | 0.31 | 0.02 | 43.2 | 0.23 | 0.01 |
| Instrumental delivery | 1.9 | −0.08 | 0.51 | 0.0 | 0.00 | 0.90 |
| Percentage of planned ‘out of hospital’ births‡‡ (n=30) | ||||||
| Straightforward birth | 0.2 | −0.08 | 0.81 | 11.0 | −0.39 | 0.15 |
| Normal birth | 0.4 | 0.15 | 0.67 | 2.7 | −0.28 | 0.43 |
| Intrapartum caesarean section | 11.2 | 0.52 | 0.28 | 17.3 | 0.41 | 0.22 |
| Instrumental delivery | 8.6 | −0.49 | 0.22 | 0.1 | 0.02 | 0.90 |
*Proportion of variance in the outcome explained by the unit characteristic.
†Percentage point increase or decrease (if negative) in the rate of the outcome for every one unit increase in the unit characteristic. For the size variable, this was per 100 women.
‡Number of births in the OU (excluding those taking place in any associated AMU) April 2009–March 2010.
§Number of delivery beds or bed spaces in the OU.
¶Percentage of shifts where there was less than one midwife on duty per woman in the delivery suite.
**AMU associated with the OU and open for the study data collection period.
††Percentage of births in the NHS trust planned to take place at home, in an FMU or AMU.
‡‡Percentage of births in the NHS trust planned to take place at home or in an FMU.
AMU, alongside midwifery unit; FMU, free-standing midwifery unit; NHS, National Health Service; OU, obstetric unit.