A feeling of well-being accompanied by a period of prosperity and birthweight in Chile: a possible link?

The aims of the study were to describe the trend in birthweight from 1985 to 2000 in Chile and ascertain the possible factors that may explain the changes in birthweight during the period. We used time series of birthweight and length at birth of all live births (n > 4,000,000). Multivariable regression analyses were carried out to assess whether the gender of the newborn, maternal education, maternal age and marital status could explain the trend in the total time series and by period. Birthweight adjusted for gestational age was analysed in terms of grams and Z scores. There was an increase in birthweight of 100 g between 1989 and 1994 that coincided with the re-establishment of democracy and economic growth in Chile. The changes in birthweight were not explained by the available independent variables and trends of caesarean section, maternal obesity and post-mature deliveries over the period. The birthweight difference between mothers with university education and those with primary education was 0.2 Z scores (equivalent to 110 g) in 1985 and was greatly reduced by 2000 (equivalent to 40 g). A positive sense of social well-being and economic growth may have influenced an increase in birthweight between 1989 and 1994 as socio-economic growth preceded and continued after the period of increasing birthweight. Our study showed a remarkable decrease in the differences in birthweight by educational level not shown in other countries of similar wealth.