Preterm births, low birth weight, and intrauterine growth restriction in three birth cohorts in Southern Brazil: 1982, 1993 and 2004

Abstract

Three birth cohort studies from 1982, 1993 and 2004, in Pelotas, Southern Brazil provided the data for this study of trends in preterm births, low birth weight, and intrauterine growth restriction. We found a slight increase in the period in the low birth weight prevalence from 9% to 10%. Intrauterine growth restriction decreased from 14.8% in 1982 to 9.4% in 1993, and subsequently increased to 12% in 2004, whereas preterm births increased markedly, from 6.3% in 1982 to 14.7% in 2004. This striking increment could not be explained by changes in maternal characteristics, as mothers in 2004 were heavier, smoked less during pregnancy and attended antenatal clinics more often and earlier than those of previous cohorts. However, pregnancy interruptions due either to caesarean sections or to inductions significantly increased. Caesareans increased from 28% in 1982 to 45% in 2004, and inductions were 2.5% in 1982 but 11.1% in 2004. The increase in preterms could be partially explained by the growing number of pregnancy interruptions, but there must be other causes since this increase was also observed among babies born by non-induced vaginal deliveries.

Determinants of preterm birth: Pelotas, Rio Grande do Sul State, Brazil, 2004 birth cohort

“…Furthermore, there was a significant reduction in the proportion of deliveries with a gestational age of 40 weeks or more between 1999 and 2002 in the USA, with a corresponding increase for gestational ages of between 34 and 39 weeks; this was observed both for births following the premature rupture of membranes and for those resulting from medical interventions 2 . Similar increases have been reported in Brazil where three birth cohorts in the city of Pelotas showed that preterm deliveries accounted for 6.3% of all births in 1982, 11.4% in 1993 and 14.7% in 2004 3 . A recent review of Brazilian population-based studies confirmed this increase 4 , which has led to a rising trend in the prevalence of low birth weight babies, and may have had contributed to the lack of success in reducing neonatal mortality in spite of improved care for preterm and low birth weight babies 5 .…”

How many low birthweight babies in low- and middle-income countries are preterm?

“…25,29,51,65 Thus, countries with high prevalence of risk factors (such as low maternal body mass index and malaria) with a resulting high prevalence of term LBW are also more likely to present high rates of preterm LBW births. In addition, a number of studies 7,23,28,45,50 show that preterm births are more frequent among poor populations. For these reasons, the current fi ndings are more biologically and epidemiologically plausible than those from earlier studies based on data collected pre-1990, which showed little variation of preterm rates across a wide range of LBW prevalences.…”

“…55,57 In addition, selected studies indicate a decreasing prevalence of IUGR in some LMICs 2,7,33 at the same time that others report substantial increases in preterm births. 7,22,27,49 Data from South America suggest that the proportion of preterm LBW babies has increased among LBW births from 59% (1992) to 70% (2000) in Uruguay (PAHO/WHO Latin American Center for Perinatology, unpublished observations) and from 46% (1996) to 62% (2004) in Brazil. 47 The latter trend is confi rmed in Brazilian birth cohort studies in the city of Pelotas, Southern Brazil, where this proportion increased from 60% in 1993 to 68% in 2004.…”

“…47 The latter trend is confi rmed in Brazilian birth cohort studies in the city of Pelotas, Southern Brazil, where this proportion increased from 60% in 1993 to 68% in 2004. 7 In view of recent changes -in opposite directions -in the prevalence of preterm and term LBW babies, we decided to generate a new set of predictive equations using data obtained from post-1990 studies. Therefore, the aim of this study was to assess the prevalence of preterm birth among low birthweight babies in low and middle-income countries.…”

Factors associated to medicine use among children from the 2004 Pelotas Birth Cohort (Brazil)

“…More methodological details of the study can be found elsewhere. 5,6 The study outcome was report of medicine use regardless of therapeutic indication or class at the three, 12-and 24-month follow-up during a 15-day recall period. Mothers were asked about their children's medicine use in the past 15 days and then medicine names were recorded and prescriptions and packages requested.…”