The purpose of this study was to analyse body size indices of newborns in Vilnius city (Lithuania) during 2005-2010 in relation with mother's education and ethnicity, and in parallel with the changes of socio-economic situation during the recent years. The present results were based on data (N = 18,084) from the Vilnius University Clinic of Obstetrics and Gynaecology. Comparison of the present Lithuanian data with other newborn studies was made. The analysis of socio-economic and demographic indicators of Lithuania, and the comparison of Gross Domestic Product of various countries was performed. The comparison of body size of newborns' data from the different countries showed that Lithuanian newborns were among the biggest babies. Some statistically significant differences in body size of newborns from different ethnic groups were established. Body length of Lithuanian newborns (M = 52.6 cm, SD = 2.5) was higher than length of Russian, Ukrainian and Romanian newborns. Body weight of Lithuanian newborns (M = 3511 g, SD = 485) was bigger than birth weight of Russian, Polish, Ukrainian and Romanian newborns. The analysis of newborns size by mother's education showed that body weight of neonates from mothers with the university education and from each other education group was bigger in comparison with the babies from respectively lower education group. The comparison of newborns weight by mother's ethnicity in relation to education level revealed nearly no discrepancies between size of newborns from mothers with the same education level at different ethnic group. The analysis of birth parameters by year has not established a statistically significant difference between the mean values for the body weight and body length of the whole investigated contingent of the full-term, single-birth newborns from Vilnius city during the 2005-2010. However, the tendency has been revealed that newborns from mothers with lower education were the most susceptible to negative economic changes after the 2008.

IntroductionThere is no global consensus as to which standards are the most appropriate for the assessment of birth weight and length. The study aimed to compare the applicability of regional and global standards to the Lithuanian newborn population by sex and gestational age, based on the prevalence of small or large for gestational age (SGA/LGA).Materials and MethodsAnalysis was performed on neonatal length and weight data obtained from the Lithuanian Medical Birth Register from 1995 to 2015 (618,235 newborns of 24–42 gestational weeks). Their distributions by gestation and sex were estimated using generalized additive models for location, scale, and shape (GAMLSS), and the results were compared with the INTERGROWTH-21st (IG-21) standard to evaluate the prevalence of SGA/LGA (10th/90th centile) at different gestational ages.ResultsThe difference in median length at term between the local reference and IG-21 was 3 cm–4 cm, while median weight at term differed by 200 g. The Lithuanian median weight at term was higher than in IG-21 by a full centile channel width, while the median length at term was higher by two channel widths. Based on the regional reference, the prevalence rates of SGA/LGA were 9.7%/10.1% for boys and 10.1%/9.9% for girls, close to the nominal 10%. Conversely, based on IG-21, the prevalence of SGA in boys/girls was less than half (4.1%/4.4%), while the prevalence of LGA was double (20.7%/19.1%).DiscussionRegional population-based neonatal references represent Lithuanian neonatal weight and length much more accurately than the global standard IG-21 which provides the prevalence rates for SGA/LGA that differ from the true values by a factor of two.

Neonatal head circumference (HC) not only represents the brain size of Homo sapiens, but is also an important health risk indicator. Addressing a lack of comparative studies on head size and its variability in term and preterm neonates from different populations, we aimed to examine neonatal HC by gestation according to a regional reference and a global standard. Retrospective analysis of data on neonatal HC obtained from the Lithuanian Medical Birth Register from 2001 to 2015 (423 999 newborns of 24–42 gestational weeks). The varying distribution by gestation and sex was estimated using GAMLSS, and the results were compared with the INTERGROWTH-21st standard. Mean HC increased with gestation in both sexes, while its fractional variability fell. The 3rd percentile matched that for INTERGROWTH-21st at all gestations, while the 50th and 97th percentiles were similar up to 27 weeks, but a full channel width higher than INTERGROWTH-21st at term. INTERGROWTH-21st facilitates the evaluation of neonatal HC in early gestations, while in later gestations, the specific features of neonatal HC of a particular population tend to be more precisely represented by regional references.