title: Trends in low birth weight: a comparison of two birth cohorts separated by a 15-year interval in Ribeirão Preto, Brazil.
abstract: The incidence and some determinants of low birth weight (LBW) were studied in two population-based cohorts of singletons born live to families in Ribeirão Preto, São Paulo State, Brazil. The first cohort comprised infants born between June 1978 and May 1979 (6750 births--population survey) and the second, infants born between May and August 1994 (2990 births--sample survey). The incidence of LBW was 7.2% in 1978-79 and 10.6% in 1994. After adjustment for confounding factors, the following determinants remained significant in 1978-79: female sex, maternal age > or = 35 years, preterm delivery, < four antenatal health visits, maternal smoking, lower level of maternal education, and manual work/unemployment. In 1994, the significant determinants were preterm delivery, maternal smoking and caesarean section. The adjusted percentage population attributable risk (PAR%) fell for the majority of risk factors but increased for caesarean section, preterm birth, multiparity (> or = 5), primiparity and non-cohabitation. The increase in the rate of LBW from 1978-79 to 1994 was higher for families with more qualified occupations, and occurred only for infants delivered at 36-40 weeks' gestational age and weighing 1500-2499 g, i.e. those most likely to be born by elective caesarean section. The caesarean section rate rose from 30.3% in 1978-79 to 51.1% in 1994. The increase in LBW was probably due to iatrogenic practices associated with elective caesarean section.
authors.affiliation: Departamento de Saúde Pública, Universidade Federal do Maranhão, Brazil.
authors.forename: A A
authors.initials: AA
authors.lastname: Silva
authors.forename: M A
authors.initials: MA
authors.lastname: Barbieri
authors.forename: U A
authors.initials: UA
authors.lastname: Gomes
authors.forename: H
authors.initials: H
authors.lastname: Bettiol
mesh_terms: D000328:Adult; D001938:Brazil / Q000453:epidemiology; D002585:Cesarean Section / Q000639:trends; D005260:Female; D006801:Humans; D015994:Incidence; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D008297:Male; D007752:Obstetric Labor, Premature / Q000453:epidemiology*; D011159:Population Surveillance; D011247:Pregnancy; D012307:Risk Factors; D012959:Socioeconomic Factors; D014504:Urban Health