Stillbirth and infant mortality in singletons by cause of death, birthweight, gestational age and birthweight-for-gestation, Newcastle upon Tyne 1961-2000.

The dramatic reduction observed in stillbirth and infant mortality over the last few decades has not been assessed by both birthweight and gestation. We have explored temporal changes in stillbirth and infant mortality in Newcastle upon Tyne, UK, by cause of death, birthweight, gestational age, birthweight standardised for gestation and infant sex during 1961-2000. We included 131 044 singleton births to mothers resident in Newcastle, including 1342 stillbirths and 1620 infant deaths. Cause-, birthweight-, gestational age- and birthweight-for-gestation-specific stillbirth (per 1000 total births) and infant mortality (per 1000 livebirths) rates were compared between 1961-80 and 1981-2000 and between individual consecutive decades. Between 1961 and 2000, total stillbirth and infant mortality rates declined dramatically from 23.4 to 4.7 per 1000 total births and from 25.7 to 5.9 per 1000 livebirths, respectively. Rates fell continuously during the first two study decades; however, from 1981-90 to 1991-2000 the decline was not statistically significant. Between 1961-80 and 1981-2000, both stillbirth and infant mortality significantly declined in all birthweight and gestational age categories and for most leading causes of death. Although the population mean birthweight during 1981-2000 [3304 g (SD +/- 569)] was significantly higher than during 1961-80 [3255 g (SD +/- 572)] (P < 0.0001), the lowest stillbirth and infant mortality rates in 1981-2000 were consistently at about 1 SD above the mean birthweight, with mortality rates increasing for babies with lower or higher weight-for-gestation. Declines in stillbirth and infant mortality in Newcastle were associated with reductions in birthweight- and gestational age-specific mortality rates and occurred in most cause-specific groups of death.