Outcomes for births booked under an independent midwife and births in NHS maternity units: matched comparison study

Abstract

Objective To compare clinical outcomes between women employing an independent midwife and comparable pregnant women using NHS services.

Design Anonymised matched cohort analysis. Cases from the database of the Independent Midwives’ Association (IMA) matched up to 1:5 with Scottish National Health Service (NHS) records for age, parity, year of birth, and socioeconomic status. Multivariable logistic regression models used to explore the relation between explanatory variables and outcomes; analyses controlled for potential confounding factors and adjusted for stratification.

Setting UK databases 2002-5.

Participants Anonymised records for 8676 women (7214 NHS; 1462 IMA).

Main outcome measures Unassisted vertex delivery, live birth, perinatal death, onset of labour, gestation, use of analgesia, duration of labour, perineal trauma, Apgar scores, admission to neonatal intensive care, infant feeding.

Results IMA cohort mothers were significantly more likely to achieve an unassisted vertex delivery than NHS cohort mothers (77.9% (1139) v 54.3% (3918); odds ratio 3.49, 95% confidence interval 2.99 to 4.07) but also significantly more likely to experience a stillbirth or a neonatal death (1.7% (25) v 0.6% (46); 5.91, 3.27 to 10.7). All odds ratios are adjusted for confounding factors. Exclusion of “high risk” cases from both cohorts showed a non-significant difference (0.5% (5) v 0.3% (18); 2.73, 0.87 to 8.55); the “low risk” IMA perinatal mortality rate is comparable with other studies of low risk births. Women in the IMA cohort had a higher incidence of pre-existing medical conditions (1.5% (22) v 1.0% (72) in the NHS cohort) and previous obstetric complications (21.0% (307) v 17.8% (1284)). The incidence of twin pregnancy was also higher (3.4% (50) v 3.1% (224)). In the IMA cohort, 66.0% of mothers (965/1462) had home births, compared with only 0.4% of NHS cohort mothers (27/7214). Spontaneous onset of labour was more common in the IMA group (96.6% (1405) v 74.5% (5365); 10.43, 7.74 to 14.0), and fewer mothers used pharmacological analgesia (40.2% (588) v 60.6% (4370); 0.42, 0.38 to 0.47). Mothers in the IMA cohort were much more likely to breast feed (88.0% (1286) v 64.0% (2759); 3.46, 2.84 to 4.20). Prematurity (4.3% (63) v 6.9% (498); 0.49, 0.35 to 0.69), low birth weight (4.0% (60) v 7.1%) (523); 0.93, 0.62 to 1.38), and rate of admission to neonatal intensive care (4.4% (65) v 9.3% (667); 0.43, 0.32 to 0.59) were all higher in the NHS dataset.

Conclusions Healthcare policy tries to direct patient choice towards clinically appropriate and practicable options; nevertheless, pregnant women are free to make decisions about birth preferences, including place of delivery and staff in attendance. While clinical outcomes across a range of variables were significantly better for women accessing an independent midwife, the significantly higher perinatal mortality rates for high risk cases in this group indicate an urgent need for a review of these cases. The significantly higher prematurity and admission rates to intensive care in the NHS cohort also indicate an urgent need for review.