Morphometric indices of thymus mass in fetuses and newborns during the early neonatal period

Objective: to identify reference values of thymus mass of foetuses and neonates of the early neonatal period depending on body weight. Material and methods. We analysed 922 autopsy reports of fetuses of 18-42 weeks of gestation and newborns of the first 7 days of life: group 1 — those who died of infectious diseases (n=67); group 2 — those who died of non-infectious diseases (n=855). Thymus mass, body weight were studied, thymic index was calculated. Spearman's criterion (R) was used to assess the correlation. A polynomial regression model using the Splines method was compiled. Results. We present data on thymus mass over a range of fetal and neonatal body weights from 300 to 5500 g. Thymus mass ranges from 1.1 to 1.48 g (for fetal masses of 300-500 g) to 12.36-15.09 (for neonatal masses of 400-5500 g). Organ weight increases with increasing gestational age, decreasing by the third day of newborn life. Median thymic index values for groups 1 and 2 were 0.32 and 0.28 (p=0.2). Regardless of the type of pathology, gestational age, and life expectancy, thymus mass correlated with body weight (Я?=0.88; p<0.001). The dynamics of changes in thymus mass (y) depending on the decimal logarithm of body weight (x) is described by the following polynomial regression equations: y=13.937x2-75.662x+104.47 for group 1 and y=16.65x2-93.487x+133.56 for group 2. Conslusion. Reference values of thymus mass of foetuses and neonates of the early neonatal period depending on body weight are were presented. It was found that there is a direct strong correlation between thymus mass and body weight.