The authors have declared that no competing interests exist.
Conceived and designed the experiments: AJ. Analyzed the data: AJ JAJMM. Wrote the paper: AJ JAJMM JM JJZ SEB JR JD. Linking the datasets: JM.
Current address: Deparment of Medical Statistics & BioInformatics, Leiden University Medical Center, Leiden, the Netherlands
To test the hypothesis that it is possible to select a group of low risk women who can start labour in midwife-led care without having increased rates of severe adverse maternal outcomes compared to women who start labour in secondary care.
We conducted a nationwide cohort study in the Netherlands, using data from 223 739 women with a singleton pregnancy between 37 and 42 weeks gestation without a previous caesarean section, with spontaneous onset of labour and a child in cephalic presentation. Information on all cases of severe acute maternal morbidity collected by the national study into ethnic determinants of maternal morbidity in the Netherlands (LEMMoN study), 1 August 2004 to 1 August 2006, was merged with data from the Netherlands Perinatal Registry of all births occurring during the same period.
Our primary outcome was severe acute maternal morbidity (SAMM, i.e. admission to an intensive care unit, uterine rupture, eclampsia or severe HELLP, major obstetric haemorrhage, and other serious events). Secondary outcomes were postpartum haemorrhage and manual removal of placenta.
Nulliparous and parous women who started labour in midwife-led care had lower rates of SAMM, postpartum haemorrhage and manual removal of placenta compared to women who started labour in secondary care. For SAMM the adjusted odds ratio’s and 95% confidence intervals were for nulliparous women: 0.57 (0.45 to 0.71) and for parous women 0.47 (0.36 to 0.62).
Our results suggest that it is possible to identify a group of women at low risk of obstetric complications who may benefit from midwife-led care. Women can be reassured that we found no evidence that midwife-led care at the onset of labour is unsafe for women in a maternity care system with a well developed risk selection and referral system.
In many Western countries obstetricians are medically responsible for birth, even if midwives or obstetric nurses provide intrapartum care.[
In previous studies, we found no increased risk of adverse perinatal or maternal outcomes among planned home versus planned hospital births for women in midwife-led care at the onset of labour.[
Concerning perinatal outcomes, one Dutch observational study showed better outcomes among women who started labour in obstetrician-led versus midwife-led care [
We used merged data from two large Dutch national datasets which enabled us to examine rare outcomes. The aim of the study was to compare the rates of severe acute maternal morbidity (SAMM), postpartum haemorrhage and manual removal of placenta among births that started in midwife-led care versus those that started in obstetrician-led care.
The Dutch maternity care system and linkage of the two national datasets that we used have been described elsewhere.[
The ethical committee of VU University Medical Center confirmed that ethical approval is not necessary for this cohort study (reference number 11/399).
We selected women with a singleton pregnancy without a known history of caesarean section who gave birth between 37 and 42 weeks of gestation and who had spontaneous onset of labour. From the LEMMoN dataset, we only included women who had SAMM after onset of labour from 37 to 42 weeks gestation. Women who had SAMM during pregnancy, but recovered and gave birth at term, were excluded.
The PRN database consists of data from three separate databases: one for primary midwife-led care (national perinatal database-1), one for secondary obstetrician-led care (national perinatal database-2), and one for paediatric care (national neonatal database). General practitioners who still attend births and a few primary care midwives do not register their data in the national register and their National Perinatal Database-1 forms will be missing. Their uncomplicated primary care births are therefore not registered. However, if complications arise, their births will be registered via the national perinatal database-2. To prevent selection bias, we excluded women who were referred during or after labour from midwife-led to obstetrician-led care but for whom the National Perinatal Database-1 form was missing.
We also excluded women who gave birth to a child in non-cephalic or unknown presentation or for whom planned level of care at the onset of labour was not known.
Hence, the study sample consisted of women with term singleton pregnancy without a known history of caesarean section, with spontaneous onset of labour and a child in cephalic presentation.
The main outcome variable was overall SAMM, which was recorded in the LEMMoN dataset. SAMM comprised five different categories which were also examined separately as secondary outcomes: admission to intensive care, uterine rupture, eclampsia or HELLP with liver haematoma or rupture, major obstetric haemorrhage (blood transfusion of four or more packed cells) and other SAMM as diagnosed by the attending clinician, such as pulmonary or amniotic fluid embolism. Other secondary outcomes were postpartum haemorrhage (defined as at least 1000 ml of blood loss) and manual removal of placenta. These outcomes were recorded in the PRN dataset. Women could have more than one adverse outcome. For example, all women who had major obstetric haemorrhage were also classified as having had postpartum haemorrhage. However, women with SAMM were only counted once for this outcome, even if they had complications in two SAMM categories; for example if they had a major obstetric haemorrhage and were admitted to intensive care.
We identified characteristics that have previously been associated with level of care at the start of labour and maternal complications: parity, maternal age, ethnic background and socioeconomic position.[
In a secondary analysis, we controlled for augmentation of labour with oxytocin and operative delivery (caesarean section, vacuum or forceps delivery), both as binary variables, because these have been found to be associated with adverse maternal outcomes.[
For births that started in midwife-led and obstetrician-led care, the numbers and percentages of the primary and secondary outcomes were calculated. Logistic regression analyses were carried out for nulliparous and parous women separately to compare rates of adverse maternal outcomes among women who started in midwife-led versus in obstetrician-led care; these were only performed for SAMM, major obstetric haemorrhage, postpartum haemorrhage and manual removal of placenta, because the other outcomes were too rare to be able to control the analyses for women’s characteristics. The crude odds ratio’s and 95% confidence intervals were calculated and multivariable logistic regression analyses were used to control for potential confounders (i.e. maternal age, ethnic background, socioeconomic position and gestational age at delivery), resulting in adjusted odds ratio’s with 95% confidence intervals. Cases with missing data were excluded.
Subsequently, the associations between planned level of care and SAMM were controlled for augmentation of labour with oxytocin and operative delivery to examine whether these factors could explain possible differences found.
Level of care at the onset of labour is based on information from the national perinatal database-1 and national perinatal database -2. For the main analyses, we used the official definition from the PRN. Sensitivity analyses were conducted for different definitions of level of care at the onset of labour; for women without discrepancies between national perinatal database-1 and national perinatal database-2 and for women with onset of labour based on the national perinatal database-1 only. Finally, we repeated the analyses without women in obstetrician-led care at the onset of labour who were referred from midwife-led to obstetrician-led care during pregnancy or for whom a risk factor was recorded which would have been a reason for antenatal referral, had they been in midwife-led care.
Of the total linked data, 240 400 women had a spontaneous onset of labour between 37 and 42 weeks gestation and no known history of caesarean section (
Women in midwife-led care at the onset of labour were more likely to be parous, less likely to give birth between 37+0 and 37+6 weeks gestation; they were less often 35 years or older; they were more often of Dutch origin and less often had a lower socioeconomic position (
Total | Midwife-led care at onset of labour | Obstetrician-led care at onset of labour | ||
---|---|---|---|---|
N = 223,739 N (%) | N = 170,439 N (%) | N = 53,300 N (%) | ||
Para 0 | 100,686 (45.0) | 76,435 (44.8) | 24,251 (45.5) | |
Para 1+ | 123,044 (55.0) | 93,995 (55.2) | 29,049 (54.5) | |
37+0 to 37+6 | 11,034 (4.9) | 7,011 (4.1) | 4,023 (7.5) | |
38+0 to 40 +6 | 163,750 (73.2) | 125,359 (73.6) | 38,391 (72.0) | |
41+0 to 41 + 6 | 48,955 (21.9) | 38,069 (22.3) | 10,886 (20.4) | |
< 25 years | 28,062 (12.5) | 21,695 (12.7) | 6,367 (11.9) | |
25 to 34 years | 150,735 (67.4) | 117,717 (69.1) | 33,018 (62.0) | |
≥ 35 years | 44,921 (20.1) | 31,011 (18.2) | 13,910 (26.1) | |
Dutch | 179,656 (80.8) | 138,493 (81.8) | 41,163 (77.6) | |
Non-Dutch | 42,812 (19.2) | 30,911 (18.2) | 11,901 (22.4) | |
High | 52,904 (24.0) | 40,804 (24.3) | 12,100 (23.2) | |
Medium99 | 99,758 (45.3) | 77,303 (46.0) | 22,455 (43.0) | |
Low | 67,765 (30.7) | 50,070 (29.8) | 17,695 (33.9) |
Missing values: parity N = 9 (0%), maternal age N = 21 (0%), ethnic background N = 1271 (0.6%), Socioeconomic position N = 3312 (1.5%)
1 P<0.05
2 P<0.001
Fewer women who started labour in midwife-led versus in obstetrician-led care received augmentation of labour (nulliparous women 27.4% versus 43.5% and parous women 6.1% versus 23.0% respectively) or had an operative delivery (nulliparous women 24.0% versus 36.5% and parous women 2.2% versus 11.5%) (
Nulliparous women, N = 100,686 | Multiparous women, N = 123,044 | |||
---|---|---|---|---|
Midwife-led care at onset of labour | Obstetrician-led care at onset of labour | Midwife-led care at onset of labour | Obstetrician-led care at onset of labour | |
N = 76,435 | N = 24,251 | N = 93,995 | N = 29,049 | |
Augmentation of labour N(%) | 20,943 (27.4) | 10,544 (43.5) | 5,739 (6.1) | 6,684 (23.0) |
Operative delivery N(%) |
18,366 (24.0) | 8,841 (36.5) | 2,049 (2.2) | 3,347 (11.5) |
*Operative delivery: caesarean section, vacuum or forceps delivery
Of all women included in the study, 574 (2.6 per 1000) had SAMM (
Total | Midwife-led care at onset of labour | Obstetrician-led care at onset of labour | |
---|---|---|---|
N = 223,739 | N = 170,439 | N = 53,300 | |
574 (2.6) | 354 (2.1) | 220 (4.1) | |
151 (0.7) | 82 (0.5) | 69 (1.3) | |
8 (0) | 4 (0) | 4 (0.1) | |
36 (0.2) | 23 (0.1) | 13 (0.2) | |
29 (0.1) | 14 (0.1) | 15 (0.3) | |
501 (2.2) | 312 (1.8) | 189 (3.5) | |
9 (0) | 5 (0) | 4 (0.1) | |
8,981 (40.7) | 6,004 (35.3) | 2,977 (59.1) | |
6,521 (29.9) | 3,671 (21.9) | 2,850 (56.9) |
HELLP = haemolysis, elevated liver enzymes and low platelet count
Missing values: postpartum haemorrhage N = 3213 (1.4%), manual removal of placenta N = 5927 (2.6%)
Women could have more than one type of adverse outcome.
Adverse outcomes were less common among women in midwife-led care at the onset of labour compared to those in obstetrician-led care for nulliparous and parous women (
Nulliparous women N = 100,686 | Parous women N = 123,044 | ||||
---|---|---|---|---|---|
Midwife-led care at onset of labour | Obstetrician-led care at onset of labour | Midwife-led care at onset of labour | Obstetrician-led care at onset of labour | ||
N = 76,435 | N = 24,251 | N = 93,995 | N = 29,049 | ||
N (N/1000) | 215 (2.8) | 127 (5.2) | 139 (1.5) | 93 (3.2) | |
Crude OR (95% CI) | 0.54 (0.43, 0.67) | Reference | 0.46 (0.36, 0.60) | Reference | |
Model 1, adj OR (95% CI) |
0.57 (0.45, 0.71) | Reference | 0.47 (0.36, 0.62) | Reference | |
Model 2, adj OR (95% CI) |
0.64 (0.51, 0.80) | Reference | 0.60 (0.45, 0.80) | Reference | |
N (N/1000) | 190 (2.5) | 110 (4.5) | 122 (1.3) | 79 (2.7) | |
Crude OR (95% CI) | 0.55 (0.43, 0.69) | Reference | 0.48 (0.36, 0.63) | Reference | |
Model 1, adj OR (95% CI) |
0.57 (0.45, 0.73) | Reference | 0.48 (0.36, 0.64) | Reference | |
Model 2, adj OR (95% CI) |
0.63 (0.49, 0.80) | Reference | 0.58 (0.43, 0.79) | Reference | |
N (N/1000) | 3389 (44.4) | 1449 (62.7) | 2615 (27.9) | 1528 (56.0) | |
Crude OR (95% CI) | 0.70 (0.65, 0.74) | Reference | 0.48 (0.45, 0.52) | Reference | |
Model 1, adj OR (95% CI) |
0.70 (0.66, 0.75) | Reference | 0.48 (0.45, 0.52) | Reference | |
Model 2, adj OR (95% CI) |
0.72 (0.68, 0.77) | Reference | 0.52 (0.49, 0.56) | Reference | |
N (N/1000) | 2347 (31.5) | 1375 (60.0) | 1324 (14.2) | 1475 (54.3) | |
Crude OR (95% CI) | 0.51 (0.48, 0.55) | Reference | 0.25 (0.23, 0.27) | Reference | |
Model 1, adj OR (95% CI) |
0.52 (0.48, 0.56) | Reference | 0.25 (0.23, 0.27) | Reference | |
Model 2, adj OR (95% CI) |
0.57 (0.53, 0.62) | Reference | 0.29 (0.27, 0.31) | Reference |
*Model 1: adjusted for gestational age, maternal age, ethnic background, socioeconomic position.
¥Model 2: adjusted for gestational age, maternal age, ethnic background, socioeconomic position, augmentation of labour and operative delivery.
Missing values: see Tables
Among nulliparous women the adjusted odds ratio’s and 95% confidence intervals for midwife-led versus obstetrician-led care were: SAMM, 0.57 (0.45 to 0.71), major obstetric haemorrhage, 0.57 (0.45 to 0.73), postpartum haemorrhage, 0.70 (0.66 to 0.75), and manual removal of placenta, 0.52 (0.48 to 0.56). Among parous women outcomes for midwife-led versus obstetrician-led care were: SAMM 0.47 (0.36 to 0.62), major obstetric haemorrhage, 0.48 (0.36 to 0.64), postpartum haemorrhage, 0.48 (0.45 to 0.52), and manual removal of placenta, 0.25 (0.23 to 0.27). When the results were controlled for augmentation of labour and operative delivery, the adjusted odds ratio’s increased. For example, when comparison of SAMM in midwife-led versus obstetrician-led care was controlled for augmentation of labour and operative delivery, the adjusted odds ratio increased from 0.57 to 0.64 (0.51 to 0.80) for nulliparous women. For parous women, the adjusted odds ratio for SAMM increased from 0.47 to 0.60 (0.45 to 0.80) after controlling for these interventions.
In total, nine women died. Of the five women who were in midwife-led care at the onset of labour, four had been referred to obstetrician-led care during labour because of meconium stained liquor. Three of them died some days or weeks after they had been discharged from hospital in good condition; one had thrombosis and two died of causes unrelated to childbirth. The other woman who was referred died of sudden collapse during labour and no cause of death was found at post-mortem examination. One woman gave birth at home and was admitted to hospital after birth where she died the next day of the consequences of eclampsia. Of the four women who were in obstetrician-led care at the onset of labour, two died of severe postpartum haemorrhage and one of eclampsia. One woman had thrombosis more than a week after birth, after she had been discharged home in good condition.
Sensitivity analyses for different definitions of level of care at the onset of labour (respectively based on a sample with no discrepancies between national perinatal database-1 and -2 and based on a definition using national perinatal database-1 only) showed similar results for all outcomes (
To our knowledge, this is the largest study so far comparing severe adverse maternal outcomes among women in midwife-led versus obstetrician-led care at the onset of labour. Nulliparous and parous women who started labour in midwife-led care had lower rates of SAMM, postpartum haemorrhage and manual removal of placenta compared to women who started labour in obstetrician-led care. The differences were reduced slightly when results were adjusted for medical interventions and more so for parous than for nulliparous women.
The main strength of our study is the large sample size. All hospitals in the Netherlands collected cases of SAMM over a period of two years.
Our study has some limitations which we described in our earlier paper.[
Risk factors can be recorded in the national perinatal database-2, but these are not obligatory items and therefore not always registered. For example, we found that a quarter of women with a previous caesarean section according to the information in the LEMMoN study, had no record of this in PRN. An association between previous caesarean section and SAMM has been demonstrated earlier.[
Other risk factors may be present in the obstetrician-led care group that we did not identify. Controlling for known risk factors only had a very small effect which suggests that other risk factors, in addition to previous caesarean section, are not always recorded. Ideally, a large prospective cohort study should be carried out to compare women with similar risk profiles. However, this may not be feasible for studying rare outcomes, such as SAMM. To improve the quality of studies using routine registration data, these data should be improved by making recording of important risk factors, such as previous caesarean section, mandatory.
Nevertheless, we excluded major risk factors. All women in the study gave birth between 37 and 42 weeks gestation and women with induction of labour or planned caesarean section were excluded. Therefore, women with risks that required induction of labour, such as postdates pregnancy and severe pre-eclampsia or intra-uterine growth restriction and women with preterm labour were excluded. The mode of onset of labour is more accurately recorded than information on other risk factors (such as previous caesarean section) because it is compulsory to record this.
It is reassuring that SAMM was not more prevalent among women that started labour in midwife-led care and, in fact, occurred less frequently.
Our results suggest that it is possible to identify a group of women at low risk of maternal complications that may benefit from midwife-led care. Although in theory it is possible that outcomes among women in midwife-led care might even have been better if they had started in obstetrician-led care, the findings are consistent with studies that compared women with similar risk profiles.[
Although low risk women receive midwife led care in the Netherlands, they do not receive continuity of care if they develop risk factors or complications. The high and increasing rate of referrals from midwife-led to obstetrician-led care during labour is a disadvantage of the current Dutch maternity care system.[
The rate of medical interventions was much lower among women that started in midwife-led care compared to obstetrician-led care. These differences contributed slightly to lower risks of adverse maternal outcomes among women in midwife-led care. Augmentation of labour, operative delivery and epidural anaesthesia have all been linked to an increased risk of postpartum haemorrhage.[
In conclusion, our study showed a lower risk of severe acute maternal morbidity, postpartum haemorrhage and manual removal of placenta among women in midwife-led care at the onset of labour compared to those in obstetrician-led care. Routine registration systems in maternity care should be improved to enhance the quality of future studies using registration data. Although risk profiles differed between both groups, our results suggest that it is possible to identify a group of women at low risk of obstetric complications who may benefit from midwife-led care. Women can be reassured that we found no evidence that midwife-led care at the onset of labour is unsafe for women in a maternity care system with a well developed risk selection and referral system.
(DOCX)
We thank the Netherlands Perinatal Registry for the use of the national database. We acknowledge all midwives, obstetricians, paediatricians, nurses and residents who routinely collect the perinatal data for this register.