The dangers of the day of birth

Authors


Abstract

Objective

To compare the risk of fetal death on the day of childbirth, with the risk of death at other ages, and with the risks of some hazardous activities, on a common scale of risk per day.

Design

Review of publicly available data.

Setting

UK.

Sample

Data extracted from the Office of National Statistics and other sources.

Methods

Data from the Office of National Statistics and other sources were used to calculate death rates at different ages expressed as rates per day of life. Death rates for different activities were also calculated as risks per day, or risks per activity, as appropriate. All risks were expressed in micromorts, the number of one in a million chances of dying. Figures on life expectancy (LE) were used to compare potential life years lost.

Main outcome measures

Daily, or unit of activity, risk of dying for different activities compared with the risk of dying on the day of childbirth.

Results

The risk of dying on the day of birth (0.43 per 1000, or 430 micromorts) exceeds that of any other average day of life until the 92nd year. It is comparable with other apparently more dangerous activities, such as undergoing major surgery. For comparison, the average risk of non-natural death per day and the increased risk from smoking one cigarette or travelling 200 miles by car are all about 1 micromort.

Conclusions

The lifetime risk of death in childbirth is low, but is concentrated in a short period, making being born a high-risk activity. Parents considering interventions to reduce these risks should be made aware of this.

Introduction

Globally, stillbirth remains a significant concern for families and health professionals. In some low-income countries, perinatal mortality rates are over 60 per 1000 births,[1] with stillbirths accounting for about half of deaths, and nearly half of these occurring intrapartum.[2] In high-income countries such as the UK, perinatal mortality is much lower (7.7 per 1000),[3] but stillbirths account for a higher proportion of deaths. Even with fetal monitoring, induction of labour, and operative delivery, UK stillbirth rates remain around 5.2 per 1000 births,[3-5] and they have not fallen significantly in the last 20 years.[6] Intrapartum stillbirths at term without contributory major congenital abnormalities often have avoidable factors identified,[7] and should be regarded as preventable.[8]

Despite this, these risks are generally perceived to be low, and as a result many parents resent the intrusiveness of hospital birth, fetal monitoring, and other recommendations. Others argue that interfering to avoid very small risks is unjustified.

Much of the risk of childbirth remains concentrated in a relatively short period: the day of labour and delivery. In addition, when death occurs so early in life it results in more life years lost on average than when death occurs at an older age.

We speculated that expressed on a daily risk scale, instead of as per thousand births, childbirth risks would appear very different. We aimed to calculate the risk of dying on each day of your life, and compare these risks with other activities or events that an individual may encounter. This information would then be used to calculate the loss of life expectancy sustained with death occurring on the day of birth.

Methods

We calculated a range of daily risks, as follows.

Fetal death on the day of delivery

UK

According to Office for National Statistics data from 2007,[3] the risk of intrapartum stillbirth is 0.13 per 1000 total births. The risk of neonatal death on the first day of life is 1.6 per 1000. If deaths on day 1 arising from congenital abnormalities (26%) and prematurity (57%) are excluded, then the risk of neonatal death on day 1 is 0.3 per 1000.[3] Therefore, we estimated the risk of death on the day of delivery for a term baby who was alive at the onset of labour to be 430 micromorts (0.43 per 1000).

USA

The risk of intrapartum stillbirth is 1.2 per 1000 total births in the USA.[9] According to the Centre for Disease Control data for 2001, the risk of early neonatal death in the USA is 3.6 per 1000 live births.[10] It is not possible to obtain the risk of death attributable to the first day from national statistics; therefore, we have arbitrarily divided the risk of early neonatal death by 7. If deaths resulting from congenital abnormalities (20%) and prematurity (29%) are excluded, then the risk of neonatal death on day 1 is 0.26 per 1000.[10] Therefore, we estimated the risk of death on the day of delivery for a term baby who was alive at the onset of labour to be 1460 micromorts.

Low-income countries

There is limited population-based data reporting on the causes of stillbirths in low-income countries.[2] We have chosen to use South Africa as an example of the risk of death on the day of delivery in a low-income country as published population data exists on the causes of perinatal deaths.[11] Globally, intrapartum stillbirth rates vary between 11.0 and 17.6 per 1000 total births in low-income countries. In South Africa the stillbirth rate is 15–24 per 1000 total births, and intrapartum stillbirth accounts for 39% of stillbirths.[2] We have therefore estimated the risk of intrapartum stillbirth in South Africa to be 7.6 per 1000 total births. Early neonatal deaths account for 0.9% of live births, 9 per 1000 total births, in South Africa.[11] We were unable to establish the risk of death on the first day of life, so have divided the risk of early neonatal death by 7, and we therefore estimated the risk of neonatal death on the first day of life to be 1.3 per 1000. If deaths on day 1 arising from congenital abnormalities (7%) and prematurity (45%) are excluded, then we estimated the risk of neonatal death on day 1 to be 0.6 per 1000 total births. Therefore, we estimated the risk of death on the day of delivery for a term baby who was alive at the onset of labour in a low-income country to be 8200 micromorts.

Mortality after birth

Data from the UK Office for National Statistics (ONS) for annual population mortality rates for each year of age were used.[12] These data are presented by the ONS as the probability of dying over a year at each age (probability 0–1). We multiplied by 1000 and divided by 365 to give a daily mortality rate per 1000.

Maternal mortality

In the last Confidential Enquiry of Maternal Deaths that occurred between 2006 and 2008 in the UK,[7] there were 261 deaths from 2 291 493 births: a maternal mortality ratio of 0.11 per 1000. However, only a minority of these occurred on the day of delivery.

When looking at the cause of death it is possible to estimate which events were likely to have occurred on the day of delivery. There were three deaths resulting from venous thromboembolism, nine deaths from haemorrhage, 13 deaths from amniotic fluid embolus, three deaths related to anaesthetic, and eleven indirect deaths that occurred on the day of delivery. Among the 53 deaths from heart disease and the 22 from hypertensive disease, it could not be deduced from the report how many occurred on the day of delivery. Therefore, at least 39 deaths occurred on the day of delivery and possibly up to 114. This gives a daily maternal mortality risk of 2–5 micromorts.

Selected risky activities

Hysterectomy

According to the VALUE study (Vaginal Abdominal or Laparoscopic Uterine Excision) there were 37 512 hysterectomies for benign disease performed in the UK in 1994–1995.[13] Eight women died before discharge from hospital. None died in theatre and three women died within 48 hours of surgery.[14] Assuming a median length of stay of 5 days this gives a daily mortality 0.04 per 1000. Fourteen deaths were reported by 6 weeks post surgery, giving an overall mortality rate for the procedure of 0.38 per thousand (0.25–0.64) or 380 micromorts.

Isolated coronary artery bypass graft

The risks associated with coronary artery bypass graft (CABG) surgery are known to vary substantially according to individual patient demographics, including age, obesity, multi-vessel disease, and medical co-morbidities. However, data from multiple centres in the USA during 2009 indicates that if the risks of single vessel graft as a primary procedure are taken, the overall operative mortality is 1.9%.[15]The median length of hospital stay postoperatively was 5 days. Although in this study operative mortality included death after discharge from hospital but during the first 30 days post-procedure, it was not possible to identify the proportion of deaths occurring in hospital. We have therefore assumed a daily mortality risk for the 5 days post-procedure as 3800 micromorts.

Presentation of risks

Daily risks were expressed as ‘micromorts’, the number of one in a million chances of death associated with each activity,[16] and compared this with widely accepted activities that carry a single micromort risk.[17-19]

Life expectancy loss

As a risk of death early in life involves the loss of more years than the same risk at later ages, we also estimated some illustrative estimates for life expectancy lost.

Results

The above risks are plotted on Figure 1. It is clear that the risk of dying on the day of birth exceeds that of any other day of an individual's life until the 92nd year. It is comparable with many other apparently risky activities. The risks expressed as micromorts are shown in Table 1.

Table 1. Daily risk of dying expressed as risk per day and micromorts per day for various activities
ActivityRisk of death per day/eventMicromorts per day/event
Population daily risk of non-natural death[20]0.001 per 10001
Smoking one cigarette[18]0.001 per 10001 per cigarette
Travel 230 miles by car[18]0.001 per 10001 per trip
Travel 6000 miles by train[18]0.001 per 10001 per trip
Travel 6 miles by motorbike[18]0.001 per 10001 per trip
Maternal childbirth risk[7]0.0017–0.0049 per 10002–5
Hysterectomy[17]0.04 per 100040
Coronary artery bypass graft[15]3.8 per 10003800
Normal fetus intrapartum death at term in the UK[3]0.43 per 1000430
Normal fetus intrapartum death at term in the USA[9, 10]1.46 per 10001460
Normal fetus intrapartum death at term in South Africa[2, 11]8.2 per 10008200
Figure 1.

Daily mortality risks at different ages and from different causes.

Life expectancy loss from risk of death at birth

As the UK life expectancy is 79 years on average, the life expectancy lost from the risks of death on the day of birth is 33.2 years per 1000 deliveries (79 × 0.42/1000).

Life expectancy loss from risk of death for a 92 year old

At 92 years of age the average life expectancy is only 3.2 years. This means that the same daily mortality rate would deprive individuals of this age just 1.3 years (3.2 × 0.42/1000).

Discussion

Main findings

Even with modern obstetric practice the risk of a baby dying on the day of its birth in the UK is greater than the average daily risk of death until the 92nd year of life. We have shown that this risk is comparable with many other high-risk activities, and results in many life years lost. Expressed as micromorts the risk is comparable with undergoing major surgery.

Strengths and limitations

It may be argued that our methodology overestimates the risk on the day of delivery as labour typically occurs within a 4- to 5-week window either side of 40 weeks of gestation. Therefore, the daily risk at say day 280 of the pregnancy would be perhaps 28 times lower; however, we have been careful not to include antepartum stillbirths in our figures. Once labour begins, the day of delivery is known, and from that point the risks are concentrated in the subsequent 24 hours or so. We have been conservative in our estimation of neonatal deaths attributable to the day of birth, as we have only included neonatal deaths that occurred on day 1, but some neonatal deaths attributable to intrapartum events do occur later.

Data published on perinatal mortality by the ONS is subject to error at multiple stages in its collection: at registration of the birth the information provided to the registrar, usually by the parent, may be inaccurate or withheld; information on the cause, duration, and weight of the stillborn infant is supplied on a certificate of stillbirth issued by the doctor or midwife present at the birth, or who examined the baby; during imputation of the data onto the database; at the point of data extraction.[20]

Interpretation

Our findings should discourage parents from underestimating the risks of childbirth and attempting to give birth away from professional help and close monitoring. The implications are wider.

Health planners, increasingly expected to allocate stretched health resources across a number of acute services, must not neglect this area of medicine where patients are at such high risk. Labour wards must continue to have adequate staffing levels with the necessary training to provide a safe environment at all times within a 24-hour period. Resources must be able to encompass essential interventions such as induction and augmentation of labour and operative deliveries to reduce intrapartum stillbirth rates. Intrapartum stillbirth rates have been proposed as a measure of quality of intrapartum care.[2]

Conclusion

When the risk of death on the day of birth is expressed as the number of years of life lost, the day of birth is relatively even riskier. In equally risky circumstances, the about to be born child has potentially much more life years at risk than the adult, who has already experienced a long life.

Disclosure of interests

We have no conflicts of interest to declare.

Contribution to authorship

The guarantor (J.G.T.) had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: J.G.T., A.C., and S.W. Acquisition of data: A.C. and S.W. Analysis and interpretation of data: A.C. and S.W. Drafting of article: A.C. and S.W. Critical revision of manuscript: K.W., K.A., D.B., and J.G.T. Study supervision: J.G.T.

Details of ethics approval

None required.

Funding

None required.

Acknowledgements

None.

Journal Club

Paper for discussion

Walker KF, Cohen AL, Walker SH, Allen KM, Baines DL, Thornton JG. The dangers of the day of birth. BJOG 2014; 121:715–719.

Scenario

A nulliparous woman in the third trimester of her pregnancy is deciding the place of her delivery. She has no significant medical history and her current pregnancy is uncomplicated. How would you counsel her?

Description of research

Participants Babies being born
Intervention Childbirth (dangers encountered on the day of birth)
Comparison Other activities encountered during the course of these individuals' lives
Outcomes Estimated daily risks of death (in micromorts, the number of 1 in a million chances of dying)
Study design Compare the estimated daily risks of death of an individual using data generated from a review of publicly available data

Discussion points

  • How would you currently counsel the woman in the scenario?
  • How did the authors generate the daily risk of death in this study?
  • Describe the methodology of this study. What are the potential biases of this methodology?
  • How might these potential biases influence the results of this study?
  • What are the possible explanations of the differences in the risks of death during birth between the UK and the USA?
  • Can you briefly summarise the results of this study? How would the results of this study influence your practice?

Suggested reading

  • Bouvier-Colle MH, Mohangoo AD, Gissler M, Novak-Antolic Z, Vutuc C, Szamotulska K, Zeitlin J; Euro-Peristat Scientific Committee. What about the mothers? An analysis of maternal mortality and morbidity in perinatal health surveillance systems in Europe. BJOG 2012;119:880–9; discussion 890.
  • Paling JE. Strategies to help patients understand risks. BMJ 2003;327(7417):745–8.
  • EYL Leung

  • Women's Health Research Unit, Queen Mary, University of London, London, UK

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