Risk factors for intrauterine growth restriction: a comparison between two Brazilian cities.

In Brazil, similar intrauterine growth restriction (IUGR) rates were observed between cities with distinct levels of socioeconomic development, challenging the current knowledge that higher rates of IUGR would necessarily be observed in poorer areas than in wealthier ones. Ribeirão Preto, a city located in the most developed area in Brazil, showed an IUGR rate of 18% in 1994, whereas this rate was 18.5% in 1997/1998 in São Luis, located in one of the poorest areas in the country. The objective of this study was to compare risk factors for IUGR in these two cities and to identify factors that are responsible for this unexpected lack of difference between the rates. Using data from two birth cohorts, including 2839 neonates who were from Ribeirão Preto and born in 1994 and 2439 neonates who were from São Luis and born in 1997/1998, a multivariable analysis was conducted to assess changes in the risk for IUGR in the poorer city compared with the wealthier one in a combined model, adjusting for some risk factors for IUGR. The wealthier city showed higher rates of maternal smoking, attendance in the private sector, and obstetric interventions than the less developed one. Differences in maternal smoking and obstetric interventions were possibly responsible for the similarity of the rates between cities. It seems that early detection of IUGR followed by cesarean section in the wealthier city is associated with increased low birth weight and IUGR rates but reduced stillbirth and infant mortality rates.