Table 20


Table 20 presents foetal deaths and foetal death ratios by gestational age for as many years as possible between 1990 and 1998.


      Description of variables: Gestational age for foetal deaths is defined as the interval, in completed weeks, between the first day of the last menstrual period of the mother and the day, month and year of delivery.


The gestational age classification used in this table is as follows under 20 weeks, 20-27 weeks, 28-31 weeks, 32-35 weeks, 36 weeks, 37-39 weeks, 40 weeks and over and unknown gestational age.  Data tabulated for alternative length of gestational categories are indicated by footnote.


The three major categories of foetal death are early foetal death or less than 20 completed weeks of gestation; intermediate foetal death of 20 but less than 28 weeks, and late foetal death of 28 weeks or more.  Three dots (...) in lower age groups indicate that only data on intermediate and/or late foetal deaths are available.


      Ratio computation: Foetal death ratios by gestational age are the number of foetal deaths which occurred in each gestational age group during the year per 1 000 total live births which occurred during the same year.  The live birth base was adapted because it is assumed to be more comparable over time from one country or area to another than the combination of live births and foetal deaths.


All ratios were computed in the Statistics Division of the United Nations using live births shown in table 1.


Foetal deaths of unknown gestational age have not been distributed proportionately.  They are included only in the total foetal death ratio.


Ratios presented in this table have been limited to those for countries or areas having at least a total of 1 000 foetal deaths in a given year.  Moreover, ratios specific for individual sub-categories based on 30 or fewer foetal deaths shown in this table are identified by the symbol (g). These ratios have been computed by the Statistics Division  of the United Nations.


      Reliability of data: Data from civil registers of late foetal deaths which are reported as incomplete (less than 90 per cent completeness) or of unknown completeness are considered unreliable and are set in italics rather than in roman type.  Table 15 and the technical notes for that table provide more detailed information on the completeness of late foetal death registration. For more information about the quality of vital statistics in general, and the information available on the basis of the completeness estimates in particular, see section 4.2 of the Technical Notes.   


      Limitations: Statistics on foetal deaths by gestational age are subject to the same qualifications that have been set forth for vital statistics in general and foetal death statistics in particular as discussed in section 4 of the Technical Notes.


The reliability of data, an indication of which is described above, is an important factor.  Of all vital statistics, the registration of foetal deaths is probably the most incomplete.


Variation in the definition of foetal deaths, and in particular late foetal deaths, also limits international comparability.  The criterion of 28 or more completed weeks of gestational age to distinguish late foetal deaths is not universally used; some countries or areas use different lengths of gestation or other criteria such as length of the foetus.  In addition, the difficulty of accurately determining gestational age further reduces comparability.


Another factor introducing variation in the definition of late foetal deaths is the practice by some countries or areas of including in late foetal death statistics infants who were born alive but died before registration of birth or within the first 24 hours after birth thus overestimating the total number of late foetal deaths.  Statistics of this type are footnoted.


The principal factor limiting comparability of data from this table is the variation in national requirements for registration of foetal deaths.  In some countries or areas, registration is required for all foetal deaths regardless of length of gestation.  In other countries or areas, registration of foetal deaths is only required following a minimum length of gestation.  In the latter case the minimum varies; both 20 and 28 weeks are common lengths of gestation after which a foetal death must be registered.


Completeness of registration further limits the comparability of foetal deaths and foetal-death ratios.  Incomplete registration may occur even when the minimum gestation for registration is 20 or 28 weeks.  Under-reporting is a more serious problem at the early stages of pregnancy when it is not always possible to determine whether or not a pregnancy has occurred.


The estimation and recording of gestational age itself are subject to considerable uncertainty.  In many cases, gestational age is estimated from the woman's recollection of the date of onset of the last menstrual period or medical records of this date, while in other cases gestational age is inferred from the weight or other characteristics of the foetus or from other information about the probable time of conception.  Moreover, gestational age can only be determined by inference for those conceptions which occur during past-portum amenorrhoea. Given the considerable variation between countries in the proportion of conceptions occurring in this period to estimate gestational age, memory errors and errors arising in the conversion of this date to the gestational age of the foetus may introduce biases into tabulations by gestational age.


In addition, foetal-death ratios are subject to the same data limitations as live births from which they are computed.  These limitations are described in the technical notes for table 1 and table 15.


      Coverage: Foetal deaths and foetal-death ratios by gestational age are shown for 43 countries or areas.



Earlier data: Foetal deaths and foetal-death ratios by gestational age have been shown previously in issues of the Demographic yearbook.  For information on years covered, readers should consult the Index.