A national study of sudden infant death syndrome in New Zealand.

Although the sudden infant death syndrome is a major component of New Zealand's high postneonatal mortality rate, little is known about its national epidemiological patterns. In this paper, based on all cases born during 1981-83, the rate of sudden infant death syndrome was 4.2/1000 livebirths. The rate declined with maternal age, birthweight, and length of gestation, but increased with parity and Registrar-General's social class. Exnuptial and male births were also at high risk, as were births to Maori and New Zealand born mothers. There was a significant seasonal pattern and a distinct north-south gradient. The rate of sudden infant death syndrome in the south of the South Island was almost twice that in the north of the North Island. These patterns are, however, similar to those of the other preventable causes of postneonatal mortality. Future research into New Zealand's postneonatal mortality needs to consider all the possible preventable causes of mortality during this period of an infant's life, rather than concentrating on only one group of at-risk infants.