Maternal, infant and social factors associated with birthweight.

IN 1900, the Infant Mortality Rate (I.M.R.) in Belfast was 153 per 1000 livebirths (Elwood, 1973). By 1971, the rate had fallen to 26 per 1000 (Registrar General's Report, 1973). This figure is, however, one of the highest in any city of comparable size in the United Kingdom. The I.M.R. in Birmingham in that year was 20 per 1000, in Bristol it was 17 and in Stoke on Trent 16, while even Teeside recorded 19.8. Elwood and Pemberton (1971) examined possible reasons why the I.M.R. in Belfast was higher than in Birmingham and concluded that 40 per cent of the excess infant mortality in Belfast was accounted for by differences between the two livebirth distributions by birthweight. Low birthweight is known to be associated with increased neonatal mortality, and also with relative mental and physical impairment of surviving infants (Weiner and Milton, 1970), so any diminution in the number of infants of low birthweight would hopefully improve the situation with regard to both mortality and morbidity. This study was undertaken in order to examine the relationship between birthweight and certain biosocial factors, and to identify some of the characteristics of mothers likely to have infants of low birthweight, and hopefully, to suggest means of reducing the incidence of low birthweight infants. Some characteristics of low birthweight infants were also studied.