Comparability of published perinatal mortality rates in Western Europe: the quantitative impact of differences in gestational age and birthweight criteria

Abstract

Two methods, one direct and one indirect, were used for adjusting these officially published rates for differences in registration laws or publication practices. For the indirect method adjustment factors were derived from an analysis of a large Finnish database using different cutoff points for gestational age and birthweight. For the direct method a common cutoff point was imposed for birthweight (1000g) and gestational age (28 completed weeks) on national perinatal mortality data, obtained from civil registration or hospital/obstetrics databases in each country. Results The published perinatal mortality rates ranged from 5.4 per 1000 total births in Sweden and Finland to 9.7 in Greece and Northern Ireland. The indirect adjustment method showed that some countries apply cutoff points for registration or publication of perinatal mortality which may raise the perinatal mortality rate by up to 17% above the most commonly used threshold for including live and stillbirths. The direct adjustment method showed that a common lower limit of 1000g for birthweight or 28 weeks for gestational age would reduce the perinatal mortality rate, but by a differing extent ranging from 14% to 40%. Both adjustment methods reduced the contrast between the countries' perinatal mortality rates, and changed their rank order. Conclusion These quantitative results confirm that international differences in countries' published perinatal mortality rates partly reflect differences between countries' criteria for registration and publication of perinatal deaths.

Perinatal health monitoring in Europe: results from the EURO-PERISTAT project

“…A short list of causes or risk factors for fetal and neonatal deaths should be developed for international comparisons [16]. Detailed information about the coding process used to derive the main cause of death for stillbirths and neonatal deaths should be compiled and analysed [17].…”

The worldwide incidence of preterm birth: a systematic review of maternal mortality and morbidity

“…Furthermore, estimates of the rate of preterm birth in developing countries are influenced by a range of factors including varying procedures used to determine gestational age, national differences in birth registration processes, heterogeneous definitions used for preterm birth, differences in perceptions of the viability of preterm infants and variations in religious practices such as local burial customs, which can discourage the registering of preterm births. 15 These issues make measurement of preterm birth and comparisons across and between developing countries difficult.…”

Canada’s pregnancy-related mortality rates: doing well but room for improvement

“…Several well-known institutions, such as the OECD, provide international rankings based on perinatal, infant and maternal mortality; however, the validity of these rankings is questionable because of wide variations in live birth and stillbirth registration practices [21][22][23][24][25]. Therefore, care must be taken when comparing perinatal health data between countries, since they use varying criteria to describe the same mortalities.…”