Skip to main content
main-content

01.12.2017 | Research article | Ausgabe 1/2017 Open Access

BMC Pregnancy and Childbirth 1/2017

A comparison of intrapartum interventions and adverse outcomes by parity in planned freestanding midwifery unit and alongside midwifery unit births: secondary analysis of ‘low risk’ births in the birthplace in England cohort

Zeitschrift:
BMC Pregnancy and Childbirth > Ausgabe 1/2017
Autoren:
Jennifer Hollowell, Yangmei Li, Kathryn Bunch, Peter Brocklehurst
Wichtige Hinweise

Electronic supplementary material

The online version of this article (doi:10.​1186/​s12884-017-1271-2) contains supplementary material, which is available to authorized users.
Abbreviations
AMU
Alongside midwifery unit
aOR
Adjusted odds ratio
BMI
Body Mass Index
CIs
Confidence intervals
CS
Caesarean section
FMU
Freestanding midwifery unit
IMD
Index of multiple deprivation
NHS
National Health Service
NICE
National Institute for Health and Care Excellence
OU
Obstetric unit

Background

In 2014, the National Institute for Health and Care Excellence (NICE) updated the intrapartum care guideline to reflect recent evidence on the benefits and risks associated with planned place of birth in different settings. The updated guideline reiterated previous guidance that birth in a midwifery-led setting was associated with a reduced risk of interventions compared with planned birth in an obstetric unit (OU) and extended the guidance to cover differences in outcomes between alongside midwifery units (AMUs) and freestanding midwifery units (FMUs):
The evidence suggested that women planning birth in a freestanding midwifery unit had lower rates of instrumental vaginal birth and caesarean section, and therefore higher rates of spontaneous vaginal birth, than women planning birth in an alongside midwifery unit.” ([1], p133)
However, the evidence underpinning the NICE conclusion regarding differences in interventions between AMUs and FMUs was derived from a re-analysis by the guideline development group of published tables from the Birthplace cohort study, and because this re-analysis was based on aggregated rather than individual data, the NICE comparison of outcomes in FMUs versus AMUs had a number of methodological limitations. First, while some of the analyses were stratified by parity, they were not adjusted for other potential confounders and did not account for study design effects such as clustering. Second, the NICE re-analysis involved multiple testing at the 5% level, raising the possibility that some of the apparently significant differences in outcomes identified in the analysis might be due to chance.
The purpose of this study was to replicate the NICE analysis using individual patient data and more robust statistical methods. Specifically the study aim was to compare key perinatal and maternal outcomes in ‘low risk’ women planning birth in an FMU versus women planning birth in an AMU, stratified by parity and adjusted for potential confounders, including complicating conditions identified at the start of care in labour, using 5% and 1% levels of significance for primary and secondary outcomes respectively.

Methods

Participants and study data

The population for this study consisted of ‘low risk’ women in the Birthplace national prospective cohort study who planned birth in an AMU or an FMU. The Birthplace cohort study setting, participants, and study data have been described in detail elsewhere [2, 3]. Briefly, the Birthplace study collected data on 79,774 ‘low’ and ‘higher risk’ births between April 2008 and April 2010 from 142 NHS trusts, 53 FMUs, 43 AMUs and a stratified random sample of 36 OUs. Women with a singleton pregnancy were eligible for inclusion if they planned a vaginal birth and received some labour care from an NHS midwife during established labour in their planned birth settings. Women who presented in preterm labour (<37 weeks’ gestation), who were ‘unbooked’ (received no antenatal care) or experienced a stillbirth prior to the onset of labour were excluded.
Planned place of birth was defined as the woman’s intended place of birth at the start of care in labour. Women were classified as ‘low risk’ if, before the onset of labour, they were not known to have any of the medical or obstetric risk factors listed in the NICE intrapartum care guideline [4].
Maternal characteristics, medical or obstetric risk factors known prior to the onset of labour, ‘complicating conditions’ noted by the midwife at the start of care in labour (for example, prolonged rupture of membranes), intrapartum interventions and adverse outcomes were recorded on a study-specific data collection form by the midwife attending the birth. Maternal and neonatal outcomes were recorded on or after day five by the midwife attending the woman.
When data for the birth episode indicated that an adverse outcome had occurred or that the baby or mother had been admitted for higher level care, additional neonatal and maternal morbidity data were extracted from the maternal and neonatal records by Birthplace local coordinating midwives using follow-up morbidity forms.

Outcome measures

For this analysis we considered the original Birthplace primary perinatal outcome (a composite measure designed to capture adverse perinatal outcomes that may be related to the quality of intrapartum care [2, 3]) and a range of outcome measures capturing maternal interventions and outcomes:
  • Perinatal outcome: ‘Birthplace primary perinatal outcome’, a composite defined as any of: stillbirth after the start of care in labour, early neonatal death, neonatal encephalopathy, meconium aspiration syndrome, brachial plexus injury, fractured humerus or clavicle.
  • Maternal interventions and outcomes: instrumental delivery (ventouse or forceps delivery); intrapartum caesarean section (CS); third or fourth degree perineal trauma; blood transfusion; admission to a higher level of care; ‘straightforward vaginal birth’, a composite measure defined as birth without intrapartum CS, instrumental delivery, third or fourth degree perineal trauma or blood transfusion. This composite measure aimed to capture birth without complications that might affect future pregnancies.
  • For completeness, we additionally considered the following interventions and outcomes: epidural or spinal analgesia, augmentation with syntocinon, immersion in water for pain relief, episiotomy, active management of the third stage and ‘initiation of breastfeeding’ (baby breastfed at least once). Detailed findings for these outcome measures are reported in the Additional file 1.

Statistical analysis

Except where indicated below, statistical methods for this study followed those in the primary Birthplace analyses [2, 3]. Logistic regression was used to calculate the odds ratios and confidence intervals for each outcome. As in previous analyses we adjusted for maternal age, ethnic group, understanding of English, marital or partner status, body mass index (BMI) in pregnancy, index of multiple deprivation (IMD) score, parity (where appropriate), and gestational age at birth. In this study we additionally adjusted for complicating conditions identified at the start of care in labour, which are associated with an increased risk of transfer [5]. Analyses were stratified by parity. The Wald test was used to test for an interaction between planned place of birth and parity. For each outcome, we calculated the number of events, the weighted incidence with confidence intervals (CIs), an unadjusted odds ratio (OR), an adjusted odds ratio (aOR) controlling for potential confounders except complicating conditions, and for the main analyses, a fully adjusted odds ratio additionally controlling for ‘complicating conditions’ as a single composite variable. Robust variance estimation and probability weights were used for reasons explained elsewhere [2, 3].
The main methodological differences between the Birthplace primary analyses [2, 3] and the analyses presented here were as follows: analyses were conducted using the AMU as the reference group and were stratified by parity; analyses were adjusted for both maternal characteristics (as before) and the presence of complicating conditions identified by the midwife at the start of care in labour; as in the primary analysis we used 95% confidence intervals for the ‘Birthplace primary perinatal outcome’ and, because Birthplace had multiple secondary outcomes, we used 99% confidence intervals for all secondary outcomes to reduce the chances of ‘false positive’ findings due to multiple comparisons. However, we also present p-values for each comparison in addition to confidence intervals.
Stata version 13.1 was used for all analyses (StataCorp LP, College Station, TX, USA).

Results

The Birthplace cohort included 27,992 eligible ‘low risk’ women planning birth in an FMU or AMU. The population for this analysis consisted of 27,938 ‘low risk’ women with known parity: 11,265 planning birth in an FMU and 16,673 planning birth in an AMU. Fifty four births were excluded because parity was unknown.

Maternal characteristics of the study sample

Table 1 shows the characteristics of ‘low risk’ women who planned FMU or AMU births by planned place of birth and parity. Amongst nulliparous women, compared with women planning to give birth in an AMU, women planning birth in an FMU were more likely to be white, have a fluent understanding of English, and live in a more socioeconomically advantaged area. There was little difference in the distribution of nulliparous women’s age, marital/partner status, BMI, gestation or baby’s birthweight. Similar differences were observed amongst multiparous women (Table 1).
Table 1
Characteristics of ‘low risk’ women and their babies by planned place of birth and parity
 
Nulliparous
Multiparous
FMU
AMU
FMU
AMU
n = 5187
n = 8350
n = 6078
n = 8323
n
%
n
%
n
%
n
%
Maternal age
 Mean (SD)
27.0
(5.69)
26.9
(5.59)
30.3
(5.39)
29.7
(5.38)
 Under 20
578
11.2
906
10.9
98
1.6
158
1.9
 20-24
1243
24.0
2064
24.8
886
14.6
1414
17.0
 25-29
1538
29.7
2552
30.6
1720
28.3
2442
29.4
 30-34
1314
25.4
2002
24.0
1930
31.8
2572
31.0
 35-39
460
8.9
755
9.1
1230
20.3
1472
17.7
 40+
47
0.9
56
0.7
207
3.4
242
2.9
 Missing
7
 
15
 
7
 
23
 
Ethnic group
 White
4779
92.2
6930
83.2
5533
91.1
6523
78.5
 Indian
46
0.9
266
3.2
41
0.7
243
2.9
 Pakistani
57
1.1
180
2.2
107
1.8
364
4.4
 Bangladeshi
42
0.8
45
0.5
105
1.7
85
1.0
 Black Caribbean
24
0.5
104
1.2
24
0.4
94
1.1
 Black African
38
0.7
191
2.3
56
0.9
328
3.9
 Mixed
61
1.2
143
1.7
63
1.0
150
1.8
 Other
138
2.7
470
5.6
146
2.4
522
6.3
 Missing
2
 
21
 
3
 
14
 
Understanding of English
 Fluent
5014
96.8
7633
91.8
5896
97.3
7530
90.8
 Some
142
2.7
560
6.7
131
2.2
613
7.4
 None
22
0.4
126
1.5
33
0.5
148
1.8
 Missing
9
 
31
 
18
 
32
 
Marital/Partner status
 Married/Living together
4608
89.9
7241
88.0
5821
96.7
7745
94.4
 Single/Unsupported
519
10.1
985
12.0
199
3.3
461
5.6
 Missing
60
 
124
 
58
 
117
 
Body mass index (kg/m 2 )
 Mean (SD)
23.7
(3.54)
23.6
(3.66)
24.4
(3.82)
24.4
(3.85)
 Not recorded
889
17.2
1432
17.2
972
16.0
1483
17.9
 10-18.4
121
2.3
243
2.9
113
1.9
194
2.3
 18.5-24.9
2738
52.8
4419
53.1
2858
47.1
3783
45.7
 25.0-29.9
1098
21.2
1713
20.6
1550
25.5
2071
25.0
 30.0-35.0
336
6.5
521
6.3
575
9.5
748
9.0
 Missing
5
 
22
 
10
 
44
 
Index of Multiple Deprivation (IMD) quintiles
 1st Least deprived
1090
21.1
1241
14.9
1405
23.2
1293
15.6
 2nd
1180
22.8
1357
16.3
1399
23.1
1281
15.4
 3rd
1094
21.2
1687
20.3
1206
19.9
1548
18.7
 4th
965
18.7
1984
23.8
1111
18.3
1860
22.4
 5th Most deprived
843
16.3
2058
24.7
941
15.5
2316
27.9
 Missing
15
 
23
 
16
 
25
 
Previous pregnancies > =24 completed weeks
 0 Nulliparous
5187
100.0
8350
100.0
N/A
N/A
N/A
N/A
 1 previous
N/A
N/A
N/A
N/A
3913
64.4
5621
67.5
 2 previous
N/A
N/A
N/A
N/A
1513
24.9
1933
23.2
 3+ previous
N/A
N/A
N/A
N/A
652
10.7
769
9.2
Gestation (completed weeks)
 Mean (SD)
39.8
(1.1)
39.7
(1.1)
39.8
(1.1)
39.7
(1.1)
 37
149
2.9
257
3.1
165
2.7
216
2.6
 38
473
9.1
798
9.6
505
8.3
766
9.2
 39
1155
22.3
1995
24.0
1512
24.9
2130
25.7
 40
1965
38.0
3178
38.2
2392
39.4
3302
39.8
 41
1379
26.7
1982
23.8
1439
23.7
1814
21.8
 42-44
51
1.0
119
1.4
57
0.9
76
0.9
 Missing
15
 
21
 
8
 
19
 
Birthweight (grams)
 Mean (SD)
3415
(420.0)
3405
(423.2)
3549
(439.3)
3519
(441.7)
 1000-2499 g
57
1.1
109
1.3
43
0.7
50
0.6
 2500-2999 g
725
14.0
1237
14.9
597
9.8
897
10.8
 3000-3499 g
2265
43.7
3581
43.0
2163
35.6
3171
38.2
 3500-3999 g
1676
32.3
2675
32.1
2342
38.6
3001
36.1
 4000-4499 g
417
8.0
665
8.0
828
13.6
1034
12.5
 4500-7500 g
46
0.9
56
0.7
100
1.6
149
1.8
 Missing
1
 
27
 
5
 
21
 
SD standard deviation
Data in bold emphasized the main headings and sub-headings
Nulliparous women were slightly more likely than multiparous women to have complicating conditions noted by the midwife at the start of care in labour, but in both groups (nulliparous and multiparous) the proportion of women with complicating conditions at the start of care in labour was similar in the two settings (Table 2).
Table 2
Complicating conditions identified at the start of care in labour in ‘low risk’ women by planned place of birth and parity
 
Nulliparous
Multiparous
FMU
AMU
FMU
AMU
n = 5187
n = 8350
n = 6078
n = 8323
n
%
n
%
n
%
n
%
Prolonged rupture of membranes (>18 h)
143
2.8
260
3.1
87
1.4
122
1.5
Meconium stained liquor
77
1.5
134
1.6
63
1.0
99
1.2
Proteinuria (1+ or more)
75
1.4
227
2.7
35
0.6
142
1.7
Hypertension
46
0.9
77
0.9
31
0.5
36
0.4
Abnormal vaginal bleeding
12
0.2
29
0.3
10
0.2
8
0.1
Non-cephalic presentation
14
0.3
18
0.2
10
0.2
11
0.1
Abnormal fetal heart rate
37
0.7
40
0.5
15
0.2
25
0.3
Other
9
0.2
8
0.1
8
0.1
9
0.1
One or more complicating conditions
368
7.1
723
8.7
251
4.1
431
5.2
Bold data indicates the row that show summary measure of all the rows above

Incidence

The absolute incidence of the outcome events considered varied markedly depending on the outcome (Table 3). For example, amongst nulliparous women, the incidence of the ‘Birthplace primary perinatal outcome’ was around 0.5% (i.e. 5 events per 1000 births), while maternal outcome rates ranged from 0.2–1% for maternal admission for higher level care through to 11–16% for instrumental delivery. Around 20–30% of nulliparous women and 3–5% of multiparous women experienced a birth that was not straightforward as defined in this analysis.
Table 3
Incidence of interventions and adverse outcomes in ‘low risk’ women by planned place of birth and parity
 
Nulliparous
Multiparous
FMU
AMU
FMU
AMU
Adverse perinatal outcome
n/1000 (95% CI)
n/1000 (95% CI)
n/1000 (95% CI)
n/1000 (95% CI)
 ‘Birthplace primary perinatal outcome’
4.5
4.7
2.7
2.4
(2.8-7.1)
(3.1-7.2)
(1.6-4.6)
(1.4-4.3)
Maternal interventions and adverse outcomes
% (99% CI)
% (99% CI)
% (99% CI)
% (99% CI)
 ‘Straightforward vaginal birth’
78.8
71.5
97.0
94.6
(75.9-81.5)
(68.1-74.7)
(96.3-97.6)
(93.3-95.6)
 Instrumental delivery (ventouse or forceps)
10.8
16.3
1.1
2.5
(8.7-13.3)
(13.9-19.1)
(0.7-1.6)
(1.9-3.3)
 Intrapartum caesarean section
6.7
7.7
0.7
1.0
(5.5-8.1)
(6.3-9.3)
(0.5-1.1)
(0.7-1.5)
 Third or fourth degree perineal trauma
4.0
4.9
0.9
1.6
(3.1-5.1)
(4.0-6.0)
(0.6-1.4)
(1.2-2.1)
 Blood transfusion
0.8
1.3
0.3
0.6
(0.5-1.1)
(0.9-1.7)
(0.2-0.6)
(0.4-0.8)
 Maternal admission for higher level care
0.2
1.0
0.1
0.4
(0.1-0.5)
(0.4-2.8)
(0.0-0.3)
(0.2-0.7)
Incidence rates are weighted to reflect each unit’s duration of participation and take the clustered nature of the data into account
Data in bold emphasized the main headings and sub-headings

Outcomes in nulliparous women

Amongst nulliparous women, those who planned birth in an FMU had highly significantly reduced odds of instrumental delivery (10.8 vs 16.3%, aOR 0.63, 99% CI 0.46–0.86, p < 0.001) and highly significantly increased odds of having a ‘straightforward vaginal birth’ (78.8 vs 71.5%, aOR 1.47, 99% CI 1.17–1.85, p < 0.001) compared with those who planned birth in an AMU (Table 4). Although not significant at the 1% level, nulliparous women who planned birth in an FMU had reduced odds of being admitted for higher level care compared with women who planned birth in an AMU (0.2 vs 1.0%, aOR 0.28, 99% CI 0.07–1.10, p = 0.016). None of the other outcomes, that is the ‘Birthplace primary perinatal outcome’, intrapartum caesarean section, third or fourth degree perineal trauma and blood transfusion, differed significantly between the two settings (p = 0.907, 0.147, 0.129 and 0.063 respectively).
Table 4
Interventions and adverse outcomes by planned place of birth (FMU vs AMU) in ‘low risk’ women by parity
 
Nulliparous
Multiparous
Perinatal outcome
Adjusted OR
95% CI
p value
Adjusted OR
95% CI
p value
 ‘Birthplace primary perinatal outcome’
0.96
(0.51-1.82)
0.907
1.14
(0.52-2.50)
0.745
Maternal outcomes
Adjusted OR
99% CI
p value
Adjusted OR
99% CI
p value
 ‘Straightforward vaginal birth’
1.47
(1.17-1.85)
<0.001**
1.86
(1.35-2.57)
<0.001**
 Instrumental delivery (ventouse or forceps)
0.63
(0.46-0.86)
<0.001**
0.41
(0.25-0.68)
<0.001**
 Intrapartum caesarean section
0.84
(0.63-1.14)
0.147
0.75
(0.41-1.38)
0.224
 Third or fourth degree perineal trauma
0.82
(0.59-1.15)
0.129
0.60
(0.36-1.00)
0.010**
 Blood transfusion
0.71
(0.44-1.14)
0.063
0.56
(0.26-1.21)
0.052
 Maternal admission for higher level care
0.28
(0.07-1.10)
0.016*
0.30
(0.07-1.20)
0.025*
Odds ratios (OR) are fully adjusted for maternal characteristics and complicating conditions identified at the start of care in labour
Reference group = AMU
**Significant differences at the 1% level
*Significant differences at the 5% level
Data in bold emphasized the main headings and sub-headings
Use of epidural or spinal analgesia (18.9 vs 24.4%), augmentation with syntocinon (13.9 vs 18.0%), episiotomy (16.0 vs 22.1%) and active management of the third stage (79.8 vs 87.2%) were significantly less common in nulliparous women who planned birth in an FMU vs an AMU. Breastfeeding initiations (84 vs 83.7%) and use of immersion in water for pain relief (51.9 vs. 37.1%) did not differ significantly between the two settings at the 1% level of significance (Additional file 1: Table S3).

Outcomes in multiparous women

Amongst multiparous women, those who planned birth in an FMU had highly significantly reduced odds of instrumental delivery (1.1 vs 2.5%, aOR 0.41, 99% CI 0.25–0.68, p < 0.001) and of third or fourth degree perineal trauma (0.9 vs 1.6%, aOR 0.60, 99% CI 0.36–1.00, p = 0.010) and highly significantly increased odds of having a ‘straightforward vaginal birth’ (97 vs 94.6%, aOR 1.86, 99% CI 1.35–2.57, p < 0.001) compared with those who planned birth in an AMU (Table 4). Although not significant at the 1% level, multiparous women who planned birth in an FMU had reduced odds of being admitted for higher level care compared with women who planned birth in an AMU (0.1 vs 0.4%, aOR 0.30, 99%CI 0.07–1.20, p = 0.025). None of the other outcomes, that is the ‘Birthplace primary perinatal outcome’, intrapartum caesarean section and blood transfusion, differed significantly between the two settings (p = 0.745, 0.224 and 0.052 respectively).
In multiparous women most other interventions were significantly less common in multiparous women who planned birth in an FMU vs an AMU (Additional file 1: Table S3): epidural or spinal analgesia (3.5 vs. 5.9%), augmentation with syntocinon (1.4 vs. 2.4%), episiotomy (2.3 vs 3.7%) and active management of the third stage (76.2 vs. 84.6%). Immersion in water for pain relief was used significantly more often by multiparous women who planned FMU birth (40.6 vs 23.2%), Breastfeeding initiation did not differ between the settings (78.2 vs. 78.6%).
Detailed results are tabulated in full in the Additional file 1.

Sensitivity analysis

When stratified by parity we did not find a significant difference between the two birth settings (FMU and AMU) in the odds of caesarean section, third or fourth degree perineal trauma (significant only for multiparous women) or blood transfusion. However, odds ratios were in the same direction and of broadly similar magnitude in nulliparous and multiparous women, and there was no strong evidence of heterogeneity (Wald test: intrapartum caesarean section p = 0.558; third or fourth degree perineal trauma p = 0.184; blood transfusion p = 0.506). We therefore conducted a post hoc combined analysis for these three outcomes, including all women (nulliparous and multiparous) and additionally adjusting for parity.
For caesarean section, this did not show a statistically significant reduction in the odds of intrapartum caesarean section in planned FMU births compared with planned AMU births (aOR 0.82, 99% CI 0.60–1.11, p = 0.093).
For third or fourth degree perineal trauma, the reduction in planned FMU births (nulliparous and multiparous combined) was not significant at the 1% level (aOR 0.76, 99% CI 0.58–1.02, p = 0.015).
For blood transfusion, combined analysis showed a highly significant reduction in the odds of blood transfusion in planned FMU births compared with planned AMU births (aOR 0.66, 99%CI 0.44–0.99, p = 0.008).

Discussion

Summary of key findings

There was no difference in adverse perinatal outcomes, as measured by the ‘Birthplace primary perinatal outcome’, between planned AMU and FMU births. The odds of an instrumental delivery were reduced in planned FMU births and the odds of having a ‘straightforward vaginal birth’ were increased in planned FMU births compared with planned AMU births. The odds of intrapartum caesarean section did not differ significantly between the two settings. The overall pattern of the findings suggested a trend towards lower intervention rates and fewer adverse maternal outcomes in planned FMU births compared with planned AMU births.

Strengths and limitations

Strengths and limitation of the Birthplace cohort study are discussed more fully elsewhere [3]. In brief, strengths include the ability to compare outcomes by planned place of birth at the start of care in labour, the large sample size, the minimisation of bias through achievement of a high response rate and the absence of self-selection bias arising from non-consent, and the ability to control for a range of potential confounders. In this analysis we have additionally controlled for complicating conditions identified at the start of care in labour, such as prolonged rupture of membranes, meconium stained liquor and proteinuria.
The study has a number of limitations. First, as in all Birthplace analyses, it is possible that the use of a composite perinatal outcome measure encompassing events of varying severity may have masked important differences between settings in more serious outcomes such as stillbirth, neonatal death and neonatal encephalopathy. Second, although we were able to control for a number of potential confounders, because of the non-randomised nature of the study it remains possible that women in the two study groups may have differed in ways that we did not measure and which may be associated with differences in outcome. For example, women opting for birth in an FMU may have a different attitude towards interventions and ‘natural birth’ than women who opt for birth in a hospital with medical facilities available on site, which may in turn influence their chances of receiving some of the interventions that we studied. Related to this, because the AMU and FMU groups were ‘self-selected’ (i.e. in most instances women will have ‘chosen’ an AMU or FMU) and this was a relatively uncommon choice at the time of the study, we cannot be certain that the findings are generalisable to other groups of women who may differ from those in the study sample. Finally, the findings relate to services available during the Birthplace data collection period (2008–2010) at which time there were fewer midwifery units than today and most AMUs were relatively small. Since 2010 the number of FMUs has remained relatively static but the number of AMUs has increased and the characteristics of these units (size, staffing, and admission criteria) may well have changed [6]. The generalisability of these findings to current models of service provision, clinical practice and to current users of midwifery-led services is unknown. These issues, and the need to undertake monitoring and evaluation of current services, are discussed more fully elsewhere [5].

Interpretation

The findings of this study are broadly consistent with the unadjusted analyses conducted as part of the NICE evidence review for the 2014 intrapartum care guideline [1] and support their conclusions that perinatal outcomes are similar in the two settings and women who plan birth in an FMU are more likely to experience a spontaneous vaginal birth than women who plan birth in an AMU. Our analyses also confirmed a reduction in serious perineal trauma in women who planned birth in an FMU compared with women who planned birth in an AMU but we cannot rule out the possibility that differences could be partly attributable to different levels of ascertainment in births planned in the two settings.
We did not observe a statistically significant reduction in intrapartum caesarean section for either nulliparous or multiparous women, or overall, so our analysis does not confirm the statistically significant reduction (unadjusted RR 0.82, 95%CI 0.73–0.93) found by NICE in their analysis of aggregated data [1]. However, although we did not find a statistically significant reduction in the odds of caesarean section in planned FMU births (p = 0.093), the observed direction of effect (odds ratio 0.82) was not inconsistent with a possible reduction in caesarean section rates in planned FMU births.
Our results show a statistically significant reduction in instrumental delivery in births planned in an FMU compared with an AMU (10.8 vs 16.3% in nulliparous women, and 1.1 vs 2.5% in multiparous women). A number of factors might explain this, including possible differences in labour management, easier access to epidurals in births planned in an AMU (which increase the risk of instrumental delivery [7]) and possibly a higher threshold for transfer for failure to progress in the second stage of labour in births planned in an FMU (since ambulance transfer is required). However, it is also possible that women who opt for birth in an AMU differ in their attitudes towards medical interventions or in other attributes that may influence outcomes and differences in provider factors such as staff seniority and experience, and organisational culture may also play a part.
We did not find that adverse perinatal outcomes differed significantly between the two settings and for both nulliparous and multiparous women the odds of the ‘Birthplace primary perinatal outcome’ were close to one. As noted above, we cannot rule out a difference in serious adverse perinatal outcomes.

Conclusions

Our analysis confirms 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 did not appear to differ between births planned in FMUs and AMUs. In general, women who planned birth in an FMU tended to experience lower intervention rates than women who planned birth in an AMU.

Acknowledgements

Not applicable.

Funding

This study was commissioned by the Healthcare Quality Improvement Partnership (HQIP) on behalf of NHS England. Birthplace combined the Evaluation of Maternity Units in England study funded in 2006 by the National Institute for Health Research Service Delivery and Organisation (NIHR SDO) programme, and the Birth at Home in England study funded in 2007 by the Department of Health Policy Research Programme (DH PRP). From January 2012, the NIHR SDO programme merged with the NIHR Health Services Research programme to establish the new NIHR Health Services and Delivery Research (NIHR HS&DR) programme. The views and opinions expressed in this paper are those of the authors and do not necessarily reflect those of the NIHR, NHS, NHS England or the Department of Health.

Availability of data and materials

Requests for access to the Birthplace data should be addressed to the current data custodian Professor Jenny Kurinczuk (Jenny.kurinczuk@npeu.ox.ac.uk).

Authors’ contributions

JH and PB conceived and developed the outline for this study; YL and JH developed the protocol and analysis plan with input from PB; KB conducted the analysis with input from YL and JH; JH drafted the manuscript with input from all authors. All authors were involved in interpretation of data, review and revision of the draft manuscript and approval of the final version.

Competing interests

The authors declare that they have no competing interests.

Consent for publication

Not applicable.

Ethics approval and consent to participate

Research ethics committee approval for the Birthplace study was obtained from the Berkshire Research Ethics Committee (MREC ref 07/H0505/151) and did not require consent to be sought from participants as no personally identifiable data were collected. The Birthplace data custodian (Professor Jenny Kurinczuk) gave permission for the Birthplace cohort study data to be used for this study.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://​creativecommons.​org/​licenses/​by/​4.​0/​), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://​creativecommons.​org/​publicdomain/​zero/​1.​0/​) applies to the data made available in this article, unless otherwise stated.
Zusatzmaterial
Additional file 1: Table S1. Adverse perinatal outcome by planned place of birth and parity. Table S2. Maternal interventions and adverse outcomes by planned place of birth and parity. Table S3. Additional maternal interventions and outcomes. (DOCX 33 kb)
12884_2017_1271_MOESM1_ESM.docx
Literatur
Über diesen Artikel

Weitere Artikel der Ausgabe 1/2017

BMC Pregnancy and Childbirth 1/2017 Zur Ausgabe

Neu im Fachgebiet Gynäkologie und Geburtshilfe

Meistgelesene Bücher aus dem Fachgebiet

2014 | Buch

Perikonzeptionelle Frauenheilkunde

Fertilitätserhalt, Prävention und Management von Schwangerschaftsrisiken

Ein Praxisbuch für alle, die in der Beratung und Betreuung von Schwangeren und Paaren mit Kinderwunsch tätig sind. Die Herausgeber und Autoren haben alle wichtigen Informationen zusammengetragen, um Frauen sicher zu beraten, zu betreuen und kompetent Verantwortung zu übernehmen.

Herausgeber:
Christian Gnoth, Peter Mallmann

2019 | Buch

Praxisbuch Gynäkologische Onkologie

Dieses kompakte und praxisrelevante Standardwerk richtet sich alle Ärzte in Klinik und Praxis, die Patientinnen mit bösartigen Tumoren des Genitales und der Mamma behandeln. Die 5. Auflage wurde komplett aktualisiert und auf der Basis …

Herausgeber:
Prof. Dr. Edgar Petru, Dr. Daniel Fink, Prof. Dr. Ossi R. Köchli, Prof. Dr. Sibylle Loibl

Mail Icon II Newsletter

Bestellen Sie unseren kostenlosen Newsletter Update Gynäkologie und bleiben Sie gut informiert – ganz bequem per eMail.

Bildnachweise