Reference values of fetal ultrasound biometry: results of a prospective cohort study in Lithuania.

Abstract

The aim of the study was to construct a reference range for the Lithuanian population for fetal biparietal diameter (BPD), occipitofrontal diameter (OFD), head circumference (HC), abdominal circumference (AC) and femur length (FL) and to compare them with the old local and current international reference values. A prospective cross-sectional study was carried out in secondary referral centres Vilnius University Hospital Santariškių Klinikos Centro Affiliate in 2008-2009 and Vilnius Maternity Hospital in 2009-2014. The fetal biometry of 556 fetuses between 12 and 42weeks gestation was performed. BPD, OFD, HC, AC and FL were measured. The data were collected and the analysis was performed using statistical programs MS Excel, SPSS and Matlab. Different regression models were fitted to calculate the mean and standard deviation at each gestational age for each parameter. The biometric measurements of HC, BPD, OFD as well as AC and FL were performed for 556 fetuses. The centile charts, tables and regression formulae of the biometric parameters were constructed. The comparison of the current charts with those of other two studies revealed no significant differences of HC centiles. AC values were similar to those presented in the international study INTERGROWTH-21 and significantly higher in comparison to the study for the Lithuanian population conducted by Ališauskas (1980). FL values, especially in late pregnancy, were significantly smaller in the INTERGROWTH-21 study compared to our charts; however, there were no significant differences of the 50th centile compared to the results from Ališauskas. We have constructed and presented centile charts, tables and regression formulae for fetal biometry for the Lithuanian population and compared them with the results of two other studies. The significant differences between our centile charts and those from INTERGROWTH-21 imply the necessity to have local standards of fetal biometry, while the differences of our results from the older study in the same population show the importance of updating fetal biometry reference charts for every generation.