Fetal Echo

Fetal Z scores

Z = [ ln(measured) - (b0 + b1 x ln(x)) ] / RMSE
x = gestational age [weeks], or femur length

Schneider 2005 sites: measurement in cm, FL in cm (page converts from mm)
Pasquini 2007 sites (isthmus, duct): measurement in mm, FL in mm

• Schneider C, McCrindle BW, Carvalho JS, Hornberger LK, McCarthy KP, Daubeney PEF. Development of Z-scores for fetal cardiac dimensions from echocardiography. Ultrasound Obstet Gynecol 2005;26(6):599-605. doi:10.1002/uog.2597. Abstract: 130 fetuses, 15–39 weeks, 17 dimensions, natural-log regressions on FL, BPD or GA.
• Pasquini L, Mellander M, Seale A, et al. Z-scores of the fetal aortic isthmus and duct: an aid to assessing arch hypoplasia. Ultrasound Obstet Gynecol 2007;29(6):628-633. doi:10.1002/uog.4021. Abstract: 221 fetuses; the Z formula above is quoted from it. Data range 18+4 to 37+3 weeks (full text).
• Coefficients: intercepts, slopes and root MSE are transcribed from the ParameterZ implementation by Dan Dyar (MIT licence, © 2009 Dan Dyar) and are identical to the printed tables (Schneider Tables 1 and 3, Pasquini Table 1; full texts read).
• Gestational age: Schneider regressed on “gestational age in completed weeks” (Equation 1), so the Schneider equations use the completed weeks and ignore the days; at + 6 days this reads up to 0.6 Z higher than a weeks + days reading would (largest at 15 weeks). Pasquini does not say how gestational age entered its regression (its methods cite Schneider 2005, which used completed weeks); its structures use weeks + days/7. If Pasquini also used completed weeks, these Z scores read up to about 0.4 lower at + 6 days (largest at 18–19 weeks). Pasquini prefers femur length as the reference.
• Names: structure names follow Schneider (LV and RV end-diastolic dimension, LV and RV inlet length) and Pasquini.
• Femur-length range: neither paper states the femur-length range of its data; the page accepts 10–76 mm (the ParameterZ input limits). Z scores beyond ±6 trigger a units check.

Verification

Checked in October 2026: all 96 coefficients (16 structures, by gestational age and by femur length) are identical to the printed tables; Schneider’s worked example (femur length 4 cm, aortic valve 0.3 cm) gives Z −1.58 (printed −1.578); Z scores and expected diameters agree with ParameterZ’s fetal calculator in every case at whole weeks and by femur length, and with Schneider’s own equation at completed weeks when days are entered. The Cardiovascular Profile Score was not verified: its point criteria come from secondary sources (below).

Cardiovascular Profile Score (Huhta)

Five categories, 2 points each (10 = normal):
hydrops, venous Doppler (UV, DV), heart size (heart/chest area),
cardiac function, arterial Doppler (umbilical artery)

• Huhta JC. Guidelines for the evaluation of heart failure in the fetus with or without hydrops. Pediatr Cardiol 2004;25(3):274-286. doi:10.1007/s00246-003-0591-3.
• Falkensammer CB, Paul J, Huhta JC. Fetal congestive heart failure: correlation of Tei-index and cardiovascular-score. J Perinat Med 2001;29(5):390-398. doi:10.1515/JPM.2001.055. Abstract: “2 points each for absence of hydrops, normal venous Doppler, heart function, arterial Doppler, and heart size, and 10/10 = normal”.
• Hofstaetter C, Hansmann M, Eik-Nes SH, Huhta JC, Luther SL. A cardiovascular profile score in the surveillance of fetal hydrops. J Matern Fetal Neonatal Med 2006;19(7):407-413. doi:10.1080/14767050600682446. Abstract: 102 hydropic fetuses; median CVPS 6 in perinatal deaths vs 7 in survivors; umbilical venous pulsations were the best predictor of adverse outcome.
• [secondary source] The point criteria in each category are taken from two open-access reviews that reproduce the Huhta table (Diagnostics 2023, doi:10.3390/diagnostics13040779, “modified from Huhta 2004”; Diagnostics 2025, doi:10.3390/diagnostics15182303). They differ slightly: one lists TR dP/dt <400 under 0 points, and the heart-size cut points are written >0.20 and <0.35 in one and ≤35% in the other. This page counts 0.20–0.35 inclusive as 2 points and notes any value exactly on a cut point. Severity bands (mild, moderate, severe) differ between sources, so none is shown.