Fetal Biometry 5.0 BETA
Important: This tool is for clinical decision support and organized reporting. Management outputs are guidance prompts and should always be integrated with the full clinical picture, interval growth, antenatal testing, maternal status, and local practice standards.
Study Setup
Measurement reminders
- UA Doppler should be taken from a free loop with fetal quiescence and averaged across consistent waveforms.
- MCA PI should be sampled consistently at the chosen site; CPR is calculated as MCA PI divided by UA PI.
- FGR logic in this calculator is driven primarily by EFW percentile, AC percentile, UA Doppler status, and end-diastolic flow status.
Ultrasound Biometry Threshold Values
Working Panel
How to measure biometry
- BPD/OFD/HC: axial head plane at thalami and cavum septi pellucidi.
- AC: true transverse abdominal plane with stomach and portal sinus visible, ribs symmetric.
- FL: full ossified diaphysis, exclude epiphyses.
- Direct EFW entry: use when a formal EFW is already available from the scan report.
How to measure Dopplers
- UA Doppler: sample from a free-floating loop of cord, fetus quiet, avoid venous signal, angle of insonation <30°, use 3 similar waveforms, and average them.
- MCA Doppler: sample the proximal to mid straight segment of the MCA in an axial head view with minimal angle and fetal rest.
- Record PI, RI, and S/D from the same high-quality tracing when possible.
Head standard used in this panel
HC in the Head panel uses exact INTERGROWTH-21st fetal head circumference equations for median and standard deviation by exact gestational age. This field is separate from the Core-panel HC used for Hadlock 4 EFW, which keeps head assessment and EFW workflow clearly separated.
How to measure head and face
- HC/BPD/OFD: standard axial plane at the thalami and cavum septi pellucidi.
- TCD: posterior fossa plane with cerebellar hemispheres and cisterna magna visualized; place calipers outer-to-outer.
- Orbital Diameter (OD) maximum internal diameter of each orbit inner orbital wall to inner orbital wall. Inner Orbital Distance (IOD), inner edge of one orbit to inner edge of the opposite orbit.Outer Orbital Distance (OOD , )binocular distance (BOD) outer edge of one orbit to outer edge of the opposite orbit. IMAGE. In Axial orbital plane with symmetric lenses.
- Mandible: true sagittal/oblique profile showing the full bony mandible; Otto reference values in this build use mandible length in centimeters.
How to measure thorax
- Thoracic circumference: transverse chest plane at the four-chamber heart view.IMAGE.
- Thoracic length: sagittal chest view from thoracic inlet/superior sternum to diaphragm.
- Clavicle/scapula: obtain the full ossified bone in a plane as close as possible to perpendicular to the beam.
How to measure GI and liver
- Stomach: measure the largest visible stomach including the pyloric region; record maximal longitudinal dimension and the AP/transverse diameters at the center of the gastric corpus.
- Interpret stomach size with caution because filling and emptying cycles can change the apparent size over short intervals; repeat assessment is helpful when clinical concern persists.
- Small bowel/colon: measure the largest lumen short-axis inner-to-inner in a coronal abdominal plane.IMAGE.
- Liver: right lobe length from superior dome to inferior edge in coronal image of abdomen.
How to measure renal and urinary tract
- Kidney length: true longitudinal kidney view, avoid including adrenal gland.
- Kidney AP and transverse: use the transverse kidney section where the renal pelvis is best visualized; measure the kidney outer-to-outer.
- Bladder longitudinal diameter: measure in a true midsagittal plane from the inner bladder dome to the inner bladder neck (largest longitudinal diameter).
How to measure skeletal parameters
- Measure each long bone in a plane where the full ossified diaphysis is visualized and as close as possible to a right angle to the ultrasound beam.
- Do not include epiphyses or adjacent shadows.
- Foot length is heel to tip of the longest toe in plantar view.
Integrated Results
FGR / Delivery Planning
Clinical synthesis
Color flags
Suggested report text
EMR-ready one-line impression
Reference Notes
Show detailed references, PMIDs, and source mapping
What changed: during the JavaScript repair pass, the short implementation-only block replaced the longer detailed references block. This version restores the detailed references and source mapping.
Current source mapping used by this build
| Calculator output | Current source family | How it is used |
|---|---|---|
| BPD percentile / z-score | Hadlock 1984 | Uses the published parameter equation and SD for gestational-age z-score support. |
| HC percentile / z-score | Hadlock 1984 | Uses the published parameter equation and SD for gestational-age z-score support. |
| AC percentile / z-score | Hadlock 1984 | Uses the published parameter equation and SD for gestational-age z-score support. |
| FL percentile / z-score | Hadlock 1984 | Uses the published parameter equation and SD for gestational-age z-score support. |
| Hadlock EFW | Hadlock 1985 / 1991 | Calculated from biometry using the selected Hadlock formula and compared with the published in utero weight standard. |
| Umbilical artery PI | INTERGROWTH-21st / Drukker 2020 | Used for gestational-age centile and z-score support and integrated FGR prompts. In this build, UA S/D uses the exact published INTERGROWTH-21st equation for skewness, mean, and coefficient of variation. |
| MCA PI / CPR | Baschat & Gembruch 2003 | Used as supportive redistribution markers rather than primary delivery triggers. |
| Head panel HC percentile / z-score | INTERGROWTH-21st fetal standard | Uses the exact published official equations for HC median and SD by exact gestational age; kept separate from the Hadlock core panel. |
| Head / thorax / GI / renal / skeletal panels | Mixed organ-specific references | Quantitative z-score and percentile outputs are interpolation-supported organ-specific estimates for panel use; thoracic circumference and thoracic length now use Chitkara table-matched percentile interpolation with an estimated z-score anchored to the table centiles; bladder longitudinal diameter now uses the Fontanella 2021 largest-LBD nomogram (15–35 weeks) with table-interpolated 5th/50th/95th centiles and contextual LUTO interpretation. TCD now uses the Pinar 2002 gestational-age mean and ±2 SD table. Kidney AP, transverse, and length dimensions are reported side-specifically using the Chitty 2003 framework. |
Core biometry and weight references
Hadlock FP, Deter RL, Harrist RB, Park SK. Estimating fetal age: computer-assisted analysis of multiple fetal growth parameters. Radiology. 1984;152:497-501. PubMed: PMID: 6739822. This is the source for the BPD, HC, AC, and FL gestational-age equations and SD values used for the current individual Hadlock parameter z-scores.
Hadlock FP, Harrist RB, Sharman RS, Deter RL, Park SK. Estimation of fetal weight with the use of head, body, and femur measurements-a prospective study. Am J Obstet Gynecol. 1985;151:333-337. PubMed: PMID 3881966. This is the classic Hadlock EFW formula paper underlying the HC+AC+FL and BPD+AC+FL pathways.
Hadlock FP, Harrist RB, Martinez-Poyer J. In utero analysis of fetal growth: a sonographic weight standard. Radiology. 1991;181:129-133. PubMed: PMID 1887021. This is the gestational-age weight standard used to contextualize EFW percentiles.
Comparator standards and alternate frameworks
INTERGROWTH-21st fetal growth standard. The earlier builds referenced INTERGROWTH-21st style head support. In the current repaired version, the active core BPD/HC/AC/FL percentiles are Hadlock-based because you specifically asked for Hadlock 4 alignment. If you want, I can add a visible framework toggle so users can switch between Hadlock core parameter percentiles and INTERGROWTH-21st comparator support.
Papageorghiou AT, Ohuma EO, Altman DG, et al. International standards for fetal growth based on serial ultrasound measurements: the Fetal Growth Longitudinal Study of the INTERGROWTH-21st Project. Lancet. 2014;384:869-879. PubMed: PMID 25209488.
Doppler references
Drukker L, Staines-Urias E, Villar J, et al. International gestational age-specific centiles for umbilical artery Doppler indices: a longitudinal prospective cohort study of the INTERGROWTH-21st Project. Am J Obstet Gynecol. 2020;222:602.e1-15. PubMed: PMID: 31954701. This is the current backbone for UA PI gestational-age centiles and z-scores in this build.
Acharya G, Wilsgaard T, Berntsen GK, Maltau JM, Kiserud T. Reference ranges for serial measurements of umbilical artery Doppler indices in the second half of pregnancy. Am J Obstet Gynecol. 2005;192:937-944. PubMed: PMID: 15746695.
Baschat AA, Gembruch U. The cerebroplacental Doppler ratio revisited. Ultrasound Obstet Gynecol. 2003;21:124-127. PubMed: PMID: 12601831.
Mari G, Deter RL, Carpenter RL, et al. Noninvasive diagnosis by Doppler ultrasonography of fetal anemia due to maternal red-cell alloimmunization. N Engl J Med. 2000;342:9-14. PubMed: PMID: 10620643.
FGR definitions and management references
Society for Maternal-Fetal Medicine (SMFM) Consult Series #52. Diagnosis and management of fetal growth restriction. Am J Obstet Gynecol. 2020. PubMed: PMID 32407785.
ACOG Practice Bulletin No. 227. Fetal Growth Restriction. 2021. PubMed: PMID: 33481528.
Head and facial biometry references
Chitty LS, Altman DG. Charts of fetal size: head measurements. BJOG. 1994. PubMed: PMID 8297866.
Merz E, Welter C, Sillek U, Pittmann P, Bahlmann F, Weber G. Orbital diameter, inner orbital distance and outer orbital distance: a growth model for fetal orbital parameters. Ultraschall in Med. 1995;16:12-17. This calculator uses the full Merz table-based 5th/50th/95th centiles with interpolation for inner and outer orbital distances.
Pinar H, Burke SH, Huang CW, Singer DB, Sung CJ. Reference values for transverse cerebellar diameter throughout gestation. Pediatr Dev Pathol. 2002 Sep-Oct;5(5):489-94. . PMID: 12192430..
Otto C, Platt LD. The fetal mandible measurement: an objective determination of fetal jaw size. Ultrasound Obstet Gynecol. 1991. PubMed: PMID 12797096. In this calculator, Otto mandible assessment is based on the gestational-age table of mean and 95% prediction limits, with interpolation between gestational weeks.
Thoracic references
Chitkara U, Rosenberg J, Chervenak FA, et al. Prenatal sonographic assessment of the fetal thorax: normal values. Am J Obstet Gynecol. 1987. PubMed: PMID 3555087.
Yarkoni S, Schmidt W, Jeanty P, et al. Clavicular measurement: a new biometric parameter for fetal evaluation. J Ultrasound Med. 1985. PubMed: PMID 3903198.
Sherer DM, Plessinger MA, Allen TA. Fetal scapular length in the ultrasonographic assessment of gestational age. J Ultrasound Med. 1994. PubMed: PMID 7933014.
GI, liver, renal, and skeletal references
Goldstein I, Reece EA, Yarkoni S, Wan M, Green JLJ, Hobbins JC. Growth of the fetal stomach in normal pregnancies. Obstet Gynecol. 1987;70:641-644.PMID: 3306513.
Kepkep K, Tuncay YA, Goynumer G, Yetim G. Nomogram of the fetal gastric size development in normal pregnancy. J Perinat Med. 2005;33:336-339.PMID: 16207120.
Lap CCM, Voskuilen CS, Pistorius LR, et al. Reference curves for the normal fetal small bowel and colon diameters; their usefulness in fetuses with suspected dilated bowel. J Matern Fetal Neonatal Med. 2020. PubMed: PMID 29985072.
Fontanella F, Groen H, Duin LK, et al. Z-scores of fetal bladder size for antenatal differential diagnosis between posterior urethral valves and urethral atresia. Ultrasound Obstet Gynecol. 2021;58:875-881.PMID: 33864313.
Chitty LS, Altman DG. Charts of fetal size: kidney and renal pelvis measurements. Prenat Diagn. 2003. PubMed: PMID 14634973.
Brennan S, Kandasamy Y, Rudd D, Schneider M, Watson D. Fetal kidney charts of a novel measurement of the renal parenchymal thickness to evaluate fetal kidney growth and potential function. Prenat Diagn. 2020. PubMed: PMID: 32277493.
van Vuuren SH, Damen-Elias HAM, Stigter RH, et al. Size and volume charts of fetal kidney, renal pelvis and adrenal gland. Ultrasound Obstet Gynecol. 2012. PubMed: PMID 22581671.
Chitty LS, Altman DG. Charts of fetal size: limb bones. BJOG. 2002. PubMed: PMID 12197373.
Implementation notes
Percentile and z-score: where a paper provides a clean mean/SD or LMS structure, the calculator can use direct z-score calculation; where a paper is better suited as a normative chart or organ-specific contextual anchor, the calculator uses interpolation-supported contextual interpretation rather than forcing an unsupported regression.