Fetal Biometry: Percentile Norms for BPD, HC, AC, FL, and Estimated Weight
Main Fetal Biometric Parameters
Standard fetal biometry in the second and third trimesters includes four basic measurements: biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). Based on these, the estimated fetal weight is calculated. Reference ranges for fetal biometry for 14–40 weeks of gestation are presented in the work by Snijders RJ, Nicolaides KH. Fetal biometry at 14-40 weeks' gestation (Ultrasound Obstet Gynecol. 1994;4:34-48).
Pregnancy Dating and First Trimester Biometry
For early dating, crown-rump length (CRL) measurement is used. The methodological basis for CRL assessment is outlined in Robinson HP, Fleming JE. A critical evaluation of sonar "crown-rump length" measurements (Br J Obstet Gynaecol. 1975;82:702-710). Normative ranges for embryo length, gestational sac diameter, and yolk sac at 6–10 weeks are provided in Papaioannou GI et al. (Fetal Diagn Ther. 2010;28(4):207-219).
Percentile Norms for Estimated Weight
To assess the estimated fetal weight and categorize it into a percentile, the Fetal Medicine Foundation weight charts are used — Nicolaides KH, Wright D, Syngelaki A, Wright A, Akolekar R. Fetal Medicine Foundation fetal and neonatal population weight charts (Ultrasound Obstet Gynecol. 2018;52:44-51). Specific numerical percentile values by weeks are not provided in the given fragments [specify].
Additional Reference Ranges
In addition to biometry, comprehensive fetal assessment uses reference ranges for Doppler measurements — pulsatility index in the umbilical artery, middle cerebral artery, and cerebroplacental ratio (Ciobanu A et al., Ultrasound Obstet Gynecol. 2019;53:465-472). The procedure for performing biometry within routine screening is regulated by ISUOG practice guidelines for mid-trimester scanning (Salomon LJ et al., Ultrasound Obstet Gynecol. 2022;59(6):840-856) and for 11–14 week scanning (Bilardo CM et al., Ultrasound Obstet Gynecol. 2023;61(1):127-143).
Frequently asked questions
What parameters are included in standard fetal biometry?
BPD, HC, AC, and FL; based on these, the estimated fetal weight is calculated.
Which reference tables are used for biometry at 14–40 weeks?
Reference ranges by Snijders RJ, Nicolaides KH. Fetal biometry at 14-40 weeks' gestation (Ultrasound Obstet Gynecol. 1994;4:34-48).
On what basis is the percentile of estimated weight assessed?
On the Fetal Medicine Foundation weight charts (Nicolaides KH et al., Ultrasound Obstet Gynecol. 2018;52:44-51).
What is used for pregnancy dating in the first trimester?
CRL measurement based on the methodology by Robinson HP, Fleming JE (1975); norms for embryo length and gestational sac at 6–10 weeks — Papaioannou GI et al. (2010).
Are specific numerical percentile values by weeks provided in the fragments?
No, specific numerical percentile values by weeks are not provided in the given sources [specify].