Definitions and rates statistics for international comparison

WHO has long recognized the importance of international comparison of perinatal and neonatal mortality and its components. One of the many tasks of WHO is to coordinate the compilation of health statistics and to encourage member countries to rely on the same definitions in order to allow for the comparison of those statistics. Events related to birth, death and the perinatal period, as well as the reporting requirements for the data from which internationally comparable statistics are drawn, are defined in the International classification of diseases (ICD) (17).

The detailed definitions and instructions are contained in the 10th edition (ICD-10) (9), Chapter 5 "Standards and reporting requirements related to fetal, perinatal, neonatal and infant mortality", which is reproduced in Annex 3. Not all sources concur with these definitions at all times. Some key issues of neonatal and perinatal mortality are mentioned below for ease of reference; however, for precise definitions the reader should refer to Annex 3.

Live birth is the complete expulsion or extraction from its mother of a product of conception, irrespective of the duration of the pregnancy, which, after such separation, breathes or shows any other evidence of life, such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles, whether or not the umbilical cord has been cut or the placenta is attached; each product of such a birth is considered liveborn.

Stillbirth or fetal death is death prior to the complete expulsion or extraction from its mother of a product of conception, irrespective of the duration of pregnancy; 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.

The perinatal period commences at 22 completed weeks (154 days) of gestation and ends seven completed days after birth.

The neonatal period begins with birth and ends 28 complete days after birth. Neonatal deaths may be subdivided into early neonatal deaths, occurring during the first seven days of life (0-6 days), and late neonatal deaths, occurring after the seventh day but before the 28th day of life (7-27 days).

The legal requirements for registration of fetal deaths and live births vary between and even within countries. WHO recommends that, if possible, all fetuses and infants weighing at least 500 g at birth, whether alive or dead, should be included in the statistics. The inclusion in national statistics of fetuses and infants weighing between 500 g and 1000 g is recommended both because of its inherent value and because it improves the coverage of reporting at 1000 g and over. For international comparison, 1000 g and/or 28 weeks gestation is recommended.

Evaluation of reporting of early deaths has shown that we may be underestimating perinatal deaths in many countries. It is likely that the decision whether to classify a delivery long before term as a spontaneous abortion or as a birth, which must be registered, may be affected by the circumstances in which the birth occurred and by the cultural and religious backgrounds of the people making the decision, as described for the past (15). For example, a stillbirth at 22 weeks of gestation must be registered as such: at 21 weeks and six days, registration is not required.

Underestimates associated with maternal death in high-mortality settings may be as high as 5% for stillbirths and 3% for neonatal deaths. These estimates are based on Egyptian survey data for 1993 and 2000 (18,19).

Developed-country historical data suggest that, as smaller and sicker babies survive, an increasing number of small babies are registered. The extent to which this affects mortality rates is difficult to assess (15).

Given these differences in recording the fact of death, it is not surprising that there are even greater differences in the way in which causes of stillbirths and neonatal deaths are recorded. One of the objectives of this report is to stimulate interest in improving the quality of reporting and clinical diagnosis of causes of perinatal death.

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