Long term trends in birth weight and length of newborns from Sofia, Bulgaria (1980–2020)

The comparison of anthropological data of newborns from different cohorts helps assessing the influence of changes in living conditions on the intrauterine growth and development. The aim of the study is to evaluate the intensity and direction of the secular trend in birth weight and length of Bulgarian newborns for 40-year period and to discuss the possible impact of different environmental factors. Data of 11,595 singleton live births (6,073 boys and 5,522 girls) with "normal birthweight" (between 2500-4500 g) gathered from the birth registers of two Obstetrics and Gynecology hospitals in Sofia, Bulgaria are included in the study. The statistical analyses are performed using SPSS 16.0. The significance of the trend is assessed by one-way ANOVA analysis. For the investigated period mean birth weight decreases from 3446.8 g to 3334.9 g and from 3321.2 g to 3179.1 g in male and female newborns respectively. Concerning birth length a statistically significant positive secular trend is observed in both sexes from 1981 to 2000 (from 50.3 cm to 51.2 cm and from 49.8 cm to 50.5 cm in male and female newborns respectively) followed by an opposite decreasing trend (1.2 cm in both sexes) after 2000. The observed tendencies probably reflect the changes in living standards and health care, population changes and changes in maternal indicators during the investigated period. As size at birth predicts not only short-term complications but also long-term health and chronic disease risk, the established decreasing trend in birth weight and length of Bulgarian newborns could be directly connected with the health of the population.