Latvian population-based birthweight charts

Large differences exist in size at birth and rates of impaired fetal growth across the world. Different factors like the environment, genetics, nutrition, and diseases can affect these discrepancies. In clinical practice, various references are often used to assess fetal growth and newborn size across populations. No such population-based birthweight charts exist in Latvia. The aim of the study was to create the local Latvian population birthweight charts that can help to assess fetal growth. The mean birth weight of 100 newborns was obtained at deliveries at 40 weeks (40+0 to 40+6) of gestation at Riga Maternity Hospital prospectively (N50) and retrospectively (N50) from August to December 2020. Only cases with accurate pregnancy dating, without any risk factors for fetal growth restriction and gestational diabetes were included. The mean birth weight of newborns at 40 weeks was 3758g (SD ±372,8g or 9,92%). The mean birth weight of girls was 3719 (SD ±318,1 or 8,55%), boys -3806g (SD ±429, or 11.2%), respectively p=0,25. The gender-specific birthweight percentiles for the Latvian population were constructed based on a Global Reference, proposing by WHO. Z-score for percentiles of normal distribution of in utero fetal growth are -0.674 for 25%, -1.282 for 10%, -1,645 for 5%, -1,881 for 3% and -2,326 for1%. The population-based gender-specific references increase the identification of abnormal newborn size at birth and therefore may better predict adverse perinatal outcomes than the non-customized fetal-weight references.