[Secular trend of birth weight in Argentina (1992-2002): a population based study]

Birth weight (BW) is considered an important measure of the health status of a population. Objectives. 1) to assess secular trends in average BW, low birth weight (LBW,<2.500 g), very low birth weight (VLBW, < 1.500 g) and BW > or = 3.000 g of liveborn infants in Argentina; 2) calculate risks of LBW, VLBW and > or = 3.000 g; 3) influence of underreported birth weight.

In this national-based study 7.113.931 liveborn infants born in Argentina from 1992 to 2002 were included. BW was assessed from the National Ministry of Public Health. Annuals mean BW and residual distribution (RD) following the Wilcox-Russell approach were calculated, and also LBW, VLBW and > or =3.000 g proportions.

A decrease of 32 g in average BW (p= 0.577) and 24 g between 2000 and 2002 (p <0.001) was observed. RD reached 4%. The significant increase in LBW (12%, p= 0.034) and VLBW (26%, p= 0.002) proportions was paralleled by a reduction of 3.6% in BW > or =3.000 g (p= 0.011, average 75.2%). Risks of being LBW and VLBW were 1.13 (95% CI 1.12-1.15) and 1.30 (1.25-1.35), respectively; for BW > or =3.000 g was 0.86 (95% CI 0.85-0.87). No significant correlations between underreported BW and proportions of LBW (r= 0.10) or VLBW (r= 0.01) were observed.

A negative secular trends of BW was observed, all categories of LBW and VLBW were increased, BW > 3.000 g was diminished and under-reported BW did not influenced these results.