Definitions

The World Health Organization (WHO), in recognizing the importance of international comparison of perinatal and neonatal mortality, coordinates the compilation of health statistics and encourages member countries to rely on the same definitions when comparing the statistics. However, there remain slight differences in the definitions of perinatal mortality between some countries, reflecting the definition of viability and resources in the individual countries.

The definitions are drawn from the 10^th edition of the International Classification of Diseases (ICD-10). The key definitions are:

In the UK the definitions are different, reflecting the survival rates and concept of viability. The present legal definitions that apply to England and Wales are as follows:

In Australia and New Zealand, stillbirth is defined as ‘Death prior to the complete expulsion or extraction from its mother of a product of conception of 20 or more completed weeks of gestation or of 400 g or more birth weight where gestation is not known. The death is indicated by the fact that after such separation the fetus does not breathe or show any other evidence of life, such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles’.

Mortality rates

The current definitions are as follows:

Incidence

Perinatal mortality rates vary widely: both between different countries and within different regions of the same country. In spite of initiatives in many countries to improve maternal and child health, there remains a significant disparity between developed countries and the developing countries.

WHO publishes global estimates on perinatal mortality rates by level of development and geographical regions. For comparison, the regions are divided into the ‘More developed, Less developed and Least developed’ with figures demonstrating a stark contrast between the regions (Table 5.1). In countries where no data collection takes place, models are produced to estimate mortality based on demographic and health surveys conducted by several agencies. Worldwide, there are over 6.3 million perinatal deaths annually, almost all of which occur in developing countries, and 27% occurring in the least developed countries alone, i.e. the sub-Saharan regions of central Africa. In developing countries, the PNMR is five times greater than in developed countries; in the least developed countries it is six time higher. It is highest in Africa, with 62 deaths per 1000 births, especially in middle and western Africa, with rates as high as 76 per 1000 births. The perinatal mortality rate in Asia is 50 per 1000 total births, with a peak of 65 per 1000 in South-central Asia.

Developed countries (Western Europe, North America, Japan, Australia and New Zealand) have seen a steady fall in the PNMR over the last 30 years. In the UK, the Centre for Maternal and Child Enquiries (CMACE) publishes annual perinatal reports and showed a statistically significant downward trend in the perinatal mortality rate, from 8.3 in 2000 to 7.5 per 1000 total births in 2008. This is due to both a statistically significant decrease in the early neonatal mortality rate (from 2.9 in 2000 to 2.5 in 2008 per 1000 live births) and a statistically significant decrease in the stillbirth rate ( from 5.4 to 5.1 per 1000 live births, respectively) (Fig. 5.1).

The reasons for this improvement include:

Sociodemographic factors and perinatal mortality

Factors that are known to affect perinatal mortality in the UK and Australia include the sociodemographic characteristics of the mother such as maternal age, deprivation, ethnicity (Table 5.2). Smoking also has a significant adverse effect on birth weight and perinatal mortality.

Causes of stillbirths

Stillbirths are the largest contributor to perinatal mortality. It is important to classify the causes of stillbirths in order to help with the understanding of the antecedents. The traditionally used systems such as the Wigglesworth and the Aberdeen (Obstetric) classifications consistently reported up to two-thirds of stillbirths as being from unexplained causes. Many newer classifications have been developed that have resulted in a significant reduction of the numbers of stillbirths being classified as unexplained. One such system, the ReCoDe (Relevant Condition at Death) system, which classifies the relevant condition present at the time of death, was developed by the Perinatal Institute, Birmingham, UK. By using this system, the Perinatal Institute identified that the most common cause of stillbirth was fetal growth restriction (43%) and only 15.2% remained unexplained. More than one condition can be classified so that both a primary and secondary code can be assigned.

Recognizing the importance of understanding the causes of stillbirths better, CMACE came up with a new classification in the 2008 Perinatal Mortality report that had an increased focus on placental pathology in attempting to recognize patterns in causes of death or identifying preventable causes. As a result of this new classification, 23% of stillbirths were unexplained. The main causes identified in the CMACE classification were (Fig. 5.2):

Causes of neonatal deaths

The global picture shows that congenital anomalies and prematurity, birth trauma and infections remain significant causes of neonatal deaths. Early neonatal deaths are mostly due to complications during pregnancy or childbirth, preterm birth and malformations; late neonatal deaths are due to neonatal tetanus and infections acquired either at home or in hospital.

Low birth weight, although not a direct cause of neonatal death, is an important association. Around 15% of newborn infants weigh less than 2500 g, ranging from 6% in developed countries to more than 30% in the poorly developed countries. Birth weight is undoubtedly an indication of maternal health and nutrition. Neonatal tetanus remains a common cause of neonatal death in settings where lack of hygiene and inadequate cord care are prevalent, as many women are not immunized against tetanus. The majority of deaths from neonatal tetanus occur between the 7th and 10th day of life.

In the UK, the neonatal classification used by CMACE looked at the primary cause and associated factors for neonatal deaths. In the past, nearly half of the neonatal deaths were due to immaturity, but the new classification restricted extreme prematurity to only cases below 22 weeks gestation, resulting in only 9.3% of neonatal deaths falling within this category. The major causes of neonatal deaths in the 2008 report are as follows (Fig. 5.3):

Maternal mortality rates

The international definition of the maternal mortality ratio (MMR) is the number of direct and indirect deaths per 100 000 live births. However, this is a problem in many countries as it is difficult to measure because the basic denominator data is lacking. A detailed report on the modelling to estimate the baseline maternal mortality ratio in underdeveloped countries is explained in the WHO publication ‘Beyond the Numbers: Reviewing Maternal Deaths and Disabilities to Make Pregnancy Safe’.

Developed countries such as the UK have the advantage of accurate denominator data, including both live births and stillbirths, and has defined its maternal mortality rate as the number of direct and indirect deaths per 100 000 maternities as a more accurate denominator to indicate the number of women at risk.

Maternities are defined as the number of pregnancies that result in a live birth at any gestation or stillbirths occurring at or after 24 completed weeks of gestation and are required to be notified by law. This enables a more detailed picture of maternal mortality rates to be established and is used for the comparison of trends over time.

Improving maternal health is one of the eight Millennium Development Goals (MDGs) adopted at the WHO 2000 Millennium Summit. The two targets for assessing progress in improving maternal health (MDG 5) are reducing MMR by 75% between 1990 and 2015, and achieving universal access to reproductive health by 2015.

In the 2010 report issued by WHO (Table 5.3), the United Nations Children’s Fund (UNICEF), the United Nations Population Fund (UNFPA) and the World Bank report entitled ‘Trends in Maternal Mortality: 1990–2008’, it is encouraging to note that the number of maternal deaths had decreased by 34% from an estimated 546 000 in 1990 to 358 000 in 2008. However, this rate of decline still falls short of the target set for MDG 5, meaning that there should be continued effort and investment in women’s health in order to achieve the goals by 2015. The report showed that 99% of all maternal deaths in 2008 occurred in developing regions, with Sub-Saharan Africa and South Asia accounting for 57% and 30% of all deaths, respectively. Globally, the four major causes of maternal death are:

In the UK, the Confidential Enquiry into maternal deaths has been publishing triennial reports since it was introduced in England and Wales in 1952. Since the UK-wide Enquiry was started, the eighth Report of the Confidential Enquiries into Maternal Deaths in the United Kingdom in the Triennium 2006–2008 was published in 2011. Published by CMACE, it investigated the deaths of 261 women who died from causes directly or indirectly related to pregnancy. In Australia similar data on maternal mortality are reported every three years by the Australian Institute of Health and Welfare.

There has been a significant reduction in the overall UK maternal death rates from 13.95 per 100 000 maternities in the previous triennium to 11.39 per 100 000 maternities in the 2006–2008 triennium (Fig 5.4). Compared with the international classification of maternal deaths from death certification alone, the UK MMR was 11.26 per 100 000 live births for 2006–2008. Downward trends were noted in maternal mortality for women from the deprived population and also in the ethnic minority groups. Similar trends have occurred in Australia with a fall in the MMR from 12.7 per 100 000 maternities in 1973–1975 to 8.4 in 2003–2005. The MMR in indigenous women (21.5 per 100 000) remains more than two and half times higher than in the non-indigenous population (7.9 per 100 000).

Major causes of maternal death in the UK

The five major direct causes of maternal death in the UK (2006–08), in order of importance, are as follows:

Although an overall decrease in the number of direct maternal deaths is noted, there has been a worrying rise in the numbers of deaths related to genital tract sepsis, particularly from community-acquired Group A streptococcal disease, making this the commonest cause of direct maternal deaths in the UK.

The number of indirect maternal deaths has remained largely unchanged since the last triennium. The commonest three indirect causes of maternal death in the year following delivery are cardiac disease, other indirect causes and neurological conditions. Many of the women with cardiac disease had lifestyle-related risk factors such as obesity, smoking and maternal age (Fig 5.5).