Severe Adverse Maternal Outcomes in Planned Home Births
Severe Adverse Maternal Outcomes in Planned Home Births
Low risk women in primary care at the onset of labour who planned to give birth at home had lower rates of severe acute maternal morbidity, postpartum haemorrhage, and manual removal of placenta compared with women who planned to give birth in hospital, but the differences were only statistically significant for parous women. Odds ratios for severe acute maternal morbidity changed slightly when we adjusted the results for medical interventions, and more so for parous than for nulliparous women.
A major strength of our study is the large sample size and the fact that all cases of severe acute maternal morbidity that occurred in all hospitals in the Netherlands were collected meticulously over two years. As far as we are aware, this is the largest study to date into the association between planned place of birth and severe adverse maternal outcomes.
Our study has some limitations as well. Firstly, because we used registration data, some were missing or may have been misclassified. For example, information on the variable “start of labour in primary or secondary care” was not always consistent between midwifery and obstetric registration. However, sensitivity analyses using different definitions of this variable generated similar results. In addition, 10,101 women were excluded because their national perinatal database-1 form was missing when they were referred during labour. Some of these women were cared for by general practitioners or midwives who do not participate in the national perinatal registration. In particular, general practitioners who still practise midwifery are often located in rural areas. This may explain the higher rate of parous women and women of Dutch ethnicity among those with a missing national perinatal database-1 form. For 18,070 women planned place of birth at the onset of labour was unknown. Their rate of severe acute maternal morbidity was comparable to that of women who planned hospital births. Even if all of these women would have a planned home birth or, alternatively, if all of them would have a planned hospital birth, the strength of the associations would have changed but the results would have been in the same direction.
Secondly, we collected the data from 2004 to 2006 and theoretically midwifery management and women’s characteristics may have changed. However, we have no reason to believe that at present planned home birth leads to more unfavourable maternal outcomes. For example, the percentage of women with a singleton pregnancy who were older than 35 years only increased from 20.5% in 2004 to 21.7% in 2006 and this percentage was 21.4% in 2010. Besides, we controlled the results for differences in maternal age.
Thirdly, although none of the women who started labour in primary care should have had an indication for secondary care according to the obstetric indication list, there may still have been differences in risk profiles between women who planned labour at home versus in hospital. We corrected the analyses for known risk factors, such as maternal age and ethnicity. Adjusting the results regarding severe acute maternal morbidity for augmentation of labour and operative delivery only led to a small reduction in the differences. This means that medical interventions explain some of the differences in severe acute maternal morbidity, which is consistent with earlier studies that showed higher rates of adverse maternal outcomes among women with medical interventions. However, the fact that odds ratios for adverse maternal outcomes were much lower for parous women than for nulliparous women, suggests that other factors played an important part. Those women who had a relatively difficult previous birth may have been more likely to plan a hospital birth next time, even if there was no official medical indication. If so, this self selection may have resulted in better outcomes among women with planned home birth. In addition, there may have been residual confounding owing to differences in characteristics that could not be identified. For example, we had no information on body mass index. Although a high body mass index is not an official medium risk indication according to the obstetric indication list, midwives may have advised these women to give birth in hospital. They may have ticked the medium risk box but they could not record body mass index as the reason for medium risk in the national perinatal database-1.
Nevertheless, our hypothesis that low risk women at the onset of labour who planned birth at home would have a higher rate of severe acute maternal morbidity compared with women who planned birth in hospital was not confirmed. Women with planned home birth had lower rates of all adverse maternal outcomes, albeit not significantly so for nulliparous women. This is consistent with other studies that found lower rates of maternal morbidity among planned home births. Concern about safety is an important reason for women to choose hospital birth, and even more so for their partners. They worry especially about transportation to hospital in case of an emergency. However, although the referral rate during labour is high in the Netherlands, only 3.4% of women are referred for urgent reasons. Our results suggest that planned home birth for low risk women is not associated with an increased risk of adverse maternal outcomes despite the possible delay in case of an emergency. Previous studies have not shown higher risks of severe adverse perinatal outcomes either for planned home births compared with planned hospital births in the Netherlands. We should emphasise that our results may only apply to regions where midwives are well trained to assist women at home births and where facilities for transfer of care and transportation in case of emergencies are adequate. In 2009, 82% of women were in hospital within 45 minutes from the moment a midwife called an ambulance in an emergency situation. The average time was 35 minutes (standard deviation 12 minutes). Travelling time to hospital is important for the safety of all births, regardless of planned place of birth. A Dutch study showed that the incidence of adverse perinatal outcomes was higher if travel time from home to hospital was more than 20 minutes, but differences were only statistically significant for women in secondary care at the onset of labour.
Planned hospital births are also associated with risks. The rate of medical interventions is lower for planned home versus planned hospital births among low risk women; for example, odds ratios for caesarean section varied between 0.31 and 0.76 in different studies. It is important to limit the use of caesarean section because of its association with various adverse outcomes at the current birth, and the risk of uterine scar rupture during the next pregnancy and birth. However, again selection bias may play a part despite all women in these studies being considered at “low risk.” Although more women with planned hospital birth may have needed interventions to ensure a good perinatal outcome, considering the large size of the differences in the rate of medical interventions between the groups, it is unlikely that these can be explained by a difference in risk profile only.
The fact that we did not find higher rates of severe acute maternal morbidity among planned home births should not lead to complacency. Every avoidable adverse maternal outcome is one too many. An audit of maternal morbidity should be used to learn from every case of severe acute maternal morbidity to improve care, optimise the risk selection system, and prevent future severe acute maternal morbidity from happening.
Discussion
Low risk women in primary care at the onset of labour who planned to give birth at home had lower rates of severe acute maternal morbidity, postpartum haemorrhage, and manual removal of placenta compared with women who planned to give birth in hospital, but the differences were only statistically significant for parous women. Odds ratios for severe acute maternal morbidity changed slightly when we adjusted the results for medical interventions, and more so for parous than for nulliparous women.
Strengths and Limitations of This Study
A major strength of our study is the large sample size and the fact that all cases of severe acute maternal morbidity that occurred in all hospitals in the Netherlands were collected meticulously over two years. As far as we are aware, this is the largest study to date into the association between planned place of birth and severe adverse maternal outcomes.
Our study has some limitations as well. Firstly, because we used registration data, some were missing or may have been misclassified. For example, information on the variable “start of labour in primary or secondary care” was not always consistent between midwifery and obstetric registration. However, sensitivity analyses using different definitions of this variable generated similar results. In addition, 10,101 women were excluded because their national perinatal database-1 form was missing when they were referred during labour. Some of these women were cared for by general practitioners or midwives who do not participate in the national perinatal registration. In particular, general practitioners who still practise midwifery are often located in rural areas. This may explain the higher rate of parous women and women of Dutch ethnicity among those with a missing national perinatal database-1 form. For 18,070 women planned place of birth at the onset of labour was unknown. Their rate of severe acute maternal morbidity was comparable to that of women who planned hospital births. Even if all of these women would have a planned home birth or, alternatively, if all of them would have a planned hospital birth, the strength of the associations would have changed but the results would have been in the same direction.
Secondly, we collected the data from 2004 to 2006 and theoretically midwifery management and women’s characteristics may have changed. However, we have no reason to believe that at present planned home birth leads to more unfavourable maternal outcomes. For example, the percentage of women with a singleton pregnancy who were older than 35 years only increased from 20.5% in 2004 to 21.7% in 2006 and this percentage was 21.4% in 2010. Besides, we controlled the results for differences in maternal age.
Thirdly, although none of the women who started labour in primary care should have had an indication for secondary care according to the obstetric indication list, there may still have been differences in risk profiles between women who planned labour at home versus in hospital. We corrected the analyses for known risk factors, such as maternal age and ethnicity. Adjusting the results regarding severe acute maternal morbidity for augmentation of labour and operative delivery only led to a small reduction in the differences. This means that medical interventions explain some of the differences in severe acute maternal morbidity, which is consistent with earlier studies that showed higher rates of adverse maternal outcomes among women with medical interventions. However, the fact that odds ratios for adverse maternal outcomes were much lower for parous women than for nulliparous women, suggests that other factors played an important part. Those women who had a relatively difficult previous birth may have been more likely to plan a hospital birth next time, even if there was no official medical indication. If so, this self selection may have resulted in better outcomes among women with planned home birth. In addition, there may have been residual confounding owing to differences in characteristics that could not be identified. For example, we had no information on body mass index. Although a high body mass index is not an official medium risk indication according to the obstetric indication list, midwives may have advised these women to give birth in hospital. They may have ticked the medium risk box but they could not record body mass index as the reason for medium risk in the national perinatal database-1.
Nevertheless, our hypothesis that low risk women at the onset of labour who planned birth at home would have a higher rate of severe acute maternal morbidity compared with women who planned birth in hospital was not confirmed. Women with planned home birth had lower rates of all adverse maternal outcomes, albeit not significantly so for nulliparous women. This is consistent with other studies that found lower rates of maternal morbidity among planned home births. Concern about safety is an important reason for women to choose hospital birth, and even more so for their partners. They worry especially about transportation to hospital in case of an emergency. However, although the referral rate during labour is high in the Netherlands, only 3.4% of women are referred for urgent reasons. Our results suggest that planned home birth for low risk women is not associated with an increased risk of adverse maternal outcomes despite the possible delay in case of an emergency. Previous studies have not shown higher risks of severe adverse perinatal outcomes either for planned home births compared with planned hospital births in the Netherlands. We should emphasise that our results may only apply to regions where midwives are well trained to assist women at home births and where facilities for transfer of care and transportation in case of emergencies are adequate. In 2009, 82% of women were in hospital within 45 minutes from the moment a midwife called an ambulance in an emergency situation. The average time was 35 minutes (standard deviation 12 minutes). Travelling time to hospital is important for the safety of all births, regardless of planned place of birth. A Dutch study showed that the incidence of adverse perinatal outcomes was higher if travel time from home to hospital was more than 20 minutes, but differences were only statistically significant for women in secondary care at the onset of labour.
Planned hospital births are also associated with risks. The rate of medical interventions is lower for planned home versus planned hospital births among low risk women; for example, odds ratios for caesarean section varied between 0.31 and 0.76 in different studies. It is important to limit the use of caesarean section because of its association with various adverse outcomes at the current birth, and the risk of uterine scar rupture during the next pregnancy and birth. However, again selection bias may play a part despite all women in these studies being considered at “low risk.” Although more women with planned hospital birth may have needed interventions to ensure a good perinatal outcome, considering the large size of the differences in the rate of medical interventions between the groups, it is unlikely that these can be explained by a difference in risk profile only.
The fact that we did not find higher rates of severe acute maternal morbidity among planned home births should not lead to complacency. Every avoidable adverse maternal outcome is one too many. An audit of maternal morbidity should be used to learn from every case of severe acute maternal morbidity to improve care, optimise the risk selection system, and prevent future severe acute maternal morbidity from happening.