Have improvements in birth weight and gestational age over 20 years influenced neonatal and infant survival?

Abstract

Low birth weight (LBW) and prematurity are important causes of neonatal and infant mortality. To improve neonatal and infant survival the government of India has therefore made efforts to reduce the proportion of LBW to 10% by the year 2000. It has been reported that the incidence of LBW decreased by 10% over a period of 20 years in Vellore. This paper examines the reduction in infant mortality from 1969-74 to 1989-94 separately and after adjusting for the effect of birth weight (BW) and gestational age (GA). Data were obtained from studies conducted in K.V. Kuppam and Vellore block on one cohort of 4220 live births in 1969-74 and one of 4753 in 1989-94. A homogeneity test and logistic regression analysis were conducted. The rate of neonatal mortality declined significantly from 34.8 to 19.1 per 1000 live births over the two decades while the infant mortality rate significantly declined from 85.9 to 49.2 per 1000 live births. The mean BWs were 2774.5 g in 1969-74 and 2845.4 g in 1989-93. The percentage of births before 37 weeks from the reported date of last menstruation decreased from 17.8 to 14.9 over the period. There was a significant decrease in neonatal and infant mortality over the period after adjusting for BW and GA. The relative risks for neonatal and infant mortality in 1989-94 significantly decreased to 0.56 and 0.55 respectively in comparison to the rates for 1969-74. Decreasing BW and preterm births were associated with higher neonatal and infant mortality. There was however no significant change in BW or GA-specific risk between the two time periods. Strategies to improve infant survival should be focused upon improving access to antenatal and intrapartum care rather than exclusively upon efforts to increase BW.