OBJECTIVES When you have completed this unit you should be able to: Explain the importance of mortality rates. Describe the concept of a mortality audit. List the important steps of audit. Keep a detailed birth register. Describe information which can be obtained from a birth register. Understand the importance of the low birth weight rate.

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All rights reserved. No part of this Perinatal Education Programme may be altered in any way without the written permission of the editorial board of the Perinatal Education Trust. To facilitate the improvement of perinatal care in Southern Africa, however, the Programme may be reproduced for teaching purposes provided due acknowledgement is given and the material is not sold for financial profit. While the advice and information in the Programme are believed to be accurate, the editorial board cannot accept responsibility or liability for any errors or omissions that may have been made.

ISBN 0 7992 2141 4

MORTALITY

46-1 WHAT IS MORTALITY?

Mortality means death. The mortality in a given area is the number of people who die in that area. Mortality is the most important measurable outcome in a health service.

46-2 WHAT IS A MORTALITY RATE?

This is the number of people who die, expressed as a proportion of all the people in that area. For example, if 10 people die in a community of 1500 people, the mortality rate is 10 per 1500.

THE MORTALITY RATE IS THE PROPORTION OF PEOPLE WHO HAVE DIED

*** Mortality rates are often also calculated for other animals or even plants.

46-3 HOW IS MORTALITY RATE EXPRESSED?

Mortality rates are usually expressed per 1000 or 100 000 individuals (i.e. as a proportion). For example, the mortality rate for newborn infants is usually given per 1000 infants delivered while the mortality rate for pregnant women is usually given per 100 000 pregnant women who deliver.

46-4 HOW CAN MORTALITY RATE BE APPLIED TO GROUPS OF PEOPLE?

A mortality rate is usually given for a specific group of people, e.g. pregnant women or newborn infants, and for a specific area or service, e.g. a town or clinic. Mortality rates may also be applied to people falling in a specific age group such as children, teenagers or the elderly.

For example, the mortality rate may be calculated only for women between the age of 20 and 25 years of age.

MORTALITY RATES ARE OFTEN CALCULATED FOR A SPECIFIC SECTION OF THE POPULATION ONLY

46-5 WHAT IS THE ANNUAL MORTALITY RATE?

This is the mortality rate calculated over the period of one year. Mortality is usually expressed as an annual rate. Sometimes the mortality rate may be expressed over a longer period such as 10 years.

46-6 SHOULD THE MORTALITY RATE BE CALCULATED FOR A SPECIAL AREA?

Yes. The mortality rate is usually calculated for a given health district or region. In order to determine the mortality rate for a health district or region, all the births and deaths in each part of that service (each clinic and hospital) must be added together. Sometimes the mortality rate is calculated for a whole province or country by combining the results of many regions.

46-7 IS THE MORTALITY RATE THE SAME FOR ALL HEALTH DISTRICTS?

No. The mortality rate often differs markedly between health districts. Usually the rates are higher for poor than industrialised districts. Similarly, rates are higher in developing than in industrialised countries.

46-8 DO MORTALITY RATES REMAIN THE SAME?

No. Mortality rates may also differ between different time periods. In most countries mortality rates have fallen over the past years.

46-9 WHY IS IT OFTEN BETTER TO KNOW THE MORTALITY RATE RATHER THAN SIMPLY THE NUMBER OF PEOPLE WHO DIE?

Knowing the rate if often more useful than simply knowing the number of individuals who die, as it allows you to compare the size of the problem between different areas or over different periods of time. A small hospital with only a few patients each year can then be compared to a large hospital with many patients.

For example, if 10 patients die out of the 1000 patients admitted to a small hospital, and 100 patients die out of the 10 000 patients admitted to the large hospital each year, then the annual mortality rate of both hospitals is the same (i.e. 10 per 1000), even though more patients died in the larger hospital. Therefore, the mortality rates of two very different sized hospitals can be fairly compared.

IT IS OFTEN MORE USEFUL TO KNOW THE MORTALITY RATE THAN JUST THE NUMBER OF PEOPLE WHO HAVE DIED

46-10 WHY WOULD ONE WANT TO KNOW THE MORTALITY RATE?

Knowing the mortality rate helps to determine both the amount of illness in a community as well as the standard of the health care. A high mortality rate suggests either a poor standard health or a poor standard of health care. Mortality rates are, therefore, very useful in assessing the needs of a community and the efficiency of the health service.

THE MORTALITY RATE REFLECTS BOTH THE AMOUNT OF ILLNESS IN A COMMUNITY AS WELL AS THE STANDARD OF HEALTH CARE

*** Under special circumstances such as revolution, widespread crime or war, the mortality rate may also be influenced by social and political factors leading to the violent deaths of healthy people.

46-11 WHY WOULD YOU WANT TO COMPARE THE MORTALITY RATES BETWEEN TWO AREAS?

This will tell you about the differences in living conditions and standards of health care in the two areas. The area with the higher mortality rate either has poorer living conditions or a less efficient health care service. The area with the higher rate may also have some specific illness such as malaria or a specific health problem such as famine.

46-12 WHY WOULD YOU WANT TO COMPARE MORTALITY RATES AT DIFFERENT TIMES?

It is very useful to compare the mortality rates in a health care service between two periods of time. In some hospitals or health districts the mortality rate may be improving while in another it may be getting worse. An increasing mortality rate indicates a fall in living conditions or a fall on the standard of health care. Sometimes an increasing mortality rate may indicate the arrival of a specific disease such as AIDS or cholera.

46-13 WHICH MORTALITY RATES ARE USUALLY RECORDED IN A MATERNITY SERVICE?

The maternal and perinatal mortality rates. The perinatal mortality rate includes both stillbirths and infant deaths in the first week of life. The following mortality rates should always be recorded:

1. Maternal mortality rate (women who die during or shortly after pregnancy).
2. Stillbirth rate (infants born dead).
3. Early neonatal death rate (infants that die in the first week of life).
4. Perinatal mortality rate (stillbirths plus early neonatal deaths).

Additional rates, which may be added, are:

5. Neonatal mortality (infants who die in the first month of life).
6. Infant mortality rate (infants who die in the first year of life).

The full definition of the maternal mortality rate is given in unit 47 while the full definitions of stillbirth, early neonatal and perinatal mortality rates are given in unit 48.

46-14 WHY IS IT IMPORTANT TO KNOW WHY MOTHERS AND INFANTS DIE?

It is very important to know, not only the mortality rates, but also why mothers and infants die in order that these deaths can be prevented by avoiding or correcting the causes of death.

The avoidable causes of maternal and perinatal deaths are discussed in detail in Unit 50.

ONLY WHEN THE CAUSES OF DEATH ARE KNOWN CAN STEPS BE TAKEN TO PREVENT FURTHER DEATHS

46-15 WHAT ARE PRIMARY CAUSES OF DEATH?

The primary cause of maternal and early neonatal deaths as well as stillbirths is the obstetric factor or condition which resulted in the death, i.e. it is the reason why the death occurred. For example, if a pregnant woman has a placental abruption and the fetus dies, the primary cause of the stillbirth is antepartum haemorrhage. Similarly, a severe antepartum haemorrhage could also be the primary cause of death of the mother. Knowing the primary causes of death helps to identify important medical conditions that need to be prevented and bad clinical practices which need to be improved.

THE PRIMARY CAUSE OF DEATH IS THE CONDITION WHICH LED TO THE MATERNAL OR PERINATAL DEATH

46-16 WHAT ARE FINAL CAUSES OF DEATH?

The final cause of maternal or early neonatal death is the event which actually caused the death (a final complication of the disease process), i.e. how the patient died. For example, if a woman has an induced abortion and dies of septic shock, the primary cause of the maternal death is the induced abortion but the final cause of death is septic shock. Similarly, if a newborn infant dies as a result of hypoxia (lack of oxygen) caused by eclampsia, the primary cause of death is eclampsia but the final cause of death is hypoxia. Knowing the final causes of death helps to identify facilities and resources, which need to be improved to prevent medical conditions resulting in death.

THE FINAL CAUSE OF DEATH IS THE FINAL EVENT WHICH ACTUALLY RESULTED IN THE MATERNAL OR EARLY NEONATAL DEATH

The primary and final causes of maternal and perinatal death are discussed in unit 49.

Note that a final cause of death is usually not recorded for stillbirths.

46-17 WHAT IS THE VALUE OF KNOWING BOTH THE PRIMARY AND FINAL CAUSES OF DEATH?

Because the correct diagnosis and management of the primary cause may prevent the complication which resulted in the death while diagnosing and treating the complication may prevent the final cause of death. For example, it would be best if placental abruption or eclampsia were prevented altogether or correctly diagnosed and treated as early as possible. If this was not possible, it is important that fetal hypoxia can be prevented or diagnosed early, and correctly managed. Every effort should be made to prevent both the primary and final causes of death.

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