New Sonographic Method for Fetuses with a Large Abdominal Circumference Improves Fetal Weight Estimation

Zusammenfassung

Ziel: Das Geburtsgewicht ist ein wichtiger prognostischer Parameter. Die gebräuchlichen Gewichtsformeln haben eine gewisse Messungenauigkeit. Der sonografische Abdomenumfang (AU) des Feten ist in den meisten Gewichtsgleichungen enthalten und hat den größten Einfluss auf die Gewichtsschätzung. Bei kleinem AU hat eine speziell hierfür entwickelte Formel die Gewichtsbestimmung verbessert. Das Ziel war es daher, eine neue Gewichtsformel für Feten mit großem AU (≥ 36,0 cm) zu entwickeln, um die Gewichtsschätzung zu optimieren. Material und Methoden: Es wurden 830 Schwangerschaften eingeschlossen. Einschlusskriterien waren eine Einlingsschwangerschaft, eine komplette Ultraschallbiometrie mit einem sonografischen AU ≥ 36,0 cm innerhalb von 7 Tagen vor Geburt sowie ein Fehlen von strukturellen oder chromosomalen Anomalien. Die Genauigkeit zweier „Best-fit“-Formeln, bestimmt mittels Vorwärts-Regressionsanalyse, wurde mit gängigen Gewichtsformeln anhand des prozentualen Fehlers (PE), des absoluten prozentualen Fehlers (APE), der „Limits of agreement“-Methode (LOA) und der kumulativen Verteilung verglichen. Ergebnisse: Die neue Formel I zeigte keinen systematischen Fehler, im Gegensatz dazu überschätzten die neue Formel II und die Routineformeln das Gewicht signifikant. Die Mediane der APEs waren bei den beiden neuen Formeln am niedrigsten (5,77 und 7,25). Weiterhin wiesen sie die engsten LOA auf. Die neue Formel I schloss bezüglich der kumulativen Verteilung auf allen Ebenen (5 %, 10 %, 15 % und 20 %) die meisten Fälle ein. Schlussfolgerung: Bei Feten mit einem Abdomenumfang von ≥ 36,0 cm hilft die speziell entwickelte Formel I, die fetale Gewichtsschätzung zu verbessern.

Abstract

Purpose: Birth weight (BW) is an important prognostic parameter for neonatal morbidity and mortality. Commonly used weight formulas lack accuracy, especially at the lower and upper end of the fetal weight range. Fetal abdominal circumference (AC) as part of most of the commonly used equations has the greatest impact on weight estimation. It has been shown that formulas specifically designed for a small fetal AC can improve weight estimation. The aim was to find out whether a new formula specifically designed for fetuses with a large AC may also improve weight determination. Materials and Methods: The study included 830 singleton pregnancies. The inclusion criteria were ultrasound examination with complete biometric parameters and an AC ≥ 36.0 cm within 7 days of delivery, and an absence of structural or chromosomal malformations. Two “best-fit” formulas were derived by forward regression analysis. The accuracy of the new formulas was compared with commonly used weight equations using percentage error (PE), absolute percentage error (APE), limits of agreement (LOA) and cumulative distribution. Results: New formula I had no systematic error while new formula II and the routine methods significantly overestimated fetal weight. The medians of the APE were the lowest among the new equations (5.77 and 7.25). The new formulas also demonstrated the narrowest LOA. Importantly, at all discrepancy levels (5 %, 10 %, 15 %, and 20 %), new formula I included significantly more cases than the commonly used methods. Conclusion: These specifically designed equations help to improve fetal weight estimation for fetuses with an AC ≥ 36.0 cm. For optimal weight estimation, we recommend using new formula I.

weight formula - abdominal circumference - macrosomia - fetal weight estimation

References

• 1 Kurmanavicius J, Burkhardt T, Wisser J et al. Ultrasonographic fetal weight estimation: accuracy of formulas and accuracy of examiners by birth weight from 500 to 5000 g.  J Perinat Med. 2004;  32 155-161
• 2 Dudley N J. A systematic review of the ultrasound estimation of fetal weight.  Ultrasound Obstet Gynecol. 2005;  25 80-89
• 3 Hasenoehrl G, Pohlhammer A, Gruber R et al. Fetal weight estimation by 2D and 3D ultrasound: comparison of six formulas.  Ultraschall in Med. 2009;  30 585-590
• 4 Siemer J, Egger N, Hart N et al. Fetal weight estimation by ultrasound: comparison of 11 different formulas and examiners with differing skill levels.  Ultraschall in Med. 2008;  29 159-164
• 5 Hoopmann M, Bernau B, Hart N et al. Do specific weight formulas for fetuses < or = 1500 g really improve weight estimation?.  Ultraschall in Med. 2010;  31 48-52
• 6 Stein W, Delfy A, Schmidt S. Prediction of shoulder dystocia – combining foetal weight estimation by ultrasound and maternal risk factors – a solution for the dilemma?.  Z Geburtshilfe Neonatol. 2009;  213 180-185
• 7 Jolly M C, Sebire N J, Harris J P et al. Risk factors for macrosomia and its clinical consequences: a study of 350311 pregnancies.  Eur J Obstet Gynecol Reprod Biol. 2003;  111 9-14
• 8 Mathew M, Machado L, Al-Ghabshi R et al. Fetal macrosomia. Risk factor and outcome.  Saudi Med J. 2005;  26 96-100
• 9 Stotland N E, Caughey A B, Breed E M et al. Risk factors and obstetric complications associated with macrosomia.  Int J Gynaecol Obstet. 2004;  87 220-226
• 10 Ecker J L, Greenberg J A, Norwitz E R et al. Birth weight as a predictor of brachial plexus injury.  Obstet Gynecol. 1997;  89 643-647
• 11 Gilbert W M, Nesbitt T S, Danielsen B. Associated factors in 1611 cases of brachial plexus injury.  Obstet Gynecol. 1999;  93 536-540
• 12 Peleg D, Hasnin J, Shalev E. Fractured clavicle and Erb’s palsy unrelated to birth trauma.  Am J Obstet Gynecol. 1997;  177 1038-1040
• 13 Abuhamad A Z. ACOG Practice Bulletin, clinical management guidelines for obstetrician-gynecologists number 98, October 2008 (replaces Practice Bulletin number 58, December 2004). Ultrasonography in pregnancy.  Obstet Gynecol. 2008;  112 951-961
• 14 Surkan P J, Hsieh C C, Johansson A L et al. Reasons for increasing trends in large for gestational age births.  Obstet Gynecol. 2004;  104 720-726
• 15 Rempen A. Vaginal ultrasonography in the first trimester. II. Quantitative parameters.  Z Geburtshilfe Perinatol. 1991;  195 163-171
• 16 Gardosi J, Geirsson R T. Routine ultrasound is the method of choice for dating pregnancy.  Br J Obstet Gynaecol. 1998;  105 933-936
• 17 Kurmanavicius J, Wright E M, Royston P et al. Fetal ultrasound biometry: 1. Head reference values.  Br J Obstet Gynaecol. 1999;  106 126-135
• 18 Kurmanavicius J, Wright E M, Royston P et al. Fetal ultrasound biometry: 2. Abdomen and femur length reference values.  Br J Obstet Gynaecol. 1999;  106 136-143
• 19 Eichhorn K H, Schramm T, Bald R et al. DEGUM grade I quality standards in obstetric ultrasound diagnosis during the 19^th–22^nd week of pregnancy.  Ultraschall in Med. 2006;  27 185-187
• 20 European Federation of Societies for Ultrasound in Medicine and Biology. Minimum training recommendations for the practice of medical ultrasound.  Ultraschall in Med. 2006;  27 79-105
• 21 Hadlock F P, Harrist R B, Sharman R S et al. Estimation of fetal weight with the use of head, body, and femur measurements – a prospective study.  Am J Obstet Gynecol. 1985;  151 333-337
• 22 Schild R L, Sachs C, Fimmers R et al. Sex-specific fetal weight prediction by ultrasound.  Ultrasound Obstet Gynecol. 2004;  23 30-35
• 23 Merz E, Lieser H, Schicketanz K H et al. Intrauterine fetal weight assessment using ultrasound. A comparison of several weight assessment methods and development of a new formula for the determination of fetal weight.  Ultraschall in Med. 1988;  9 15-24
• 24 Pitman E JG. A note on normal correlation.  Biometrika. 1939;  31 9-12
• 25 Snedecor G W, Cochran W G. Comparison of two correlated variances in paired samples. In Statistical Methods.. 8 ed. Ames: Iowa State University Press; 1989: 192-193
• 26 Bland J M, Altman D G. Statistical methods for assessing agreement between two methods of clinical measurement.  Lancet. 1986;  1 307-310
• 27 Melamed N, Yogev Y, Meizner I et al. Sonographic fetal weight estimation: which model should be used?.  J Ultrasound Med. 2009;  28 617-629
• 28 Siemer J, Wolf T, Hart N et al. Increased accuracy of fetal weight estimation with a gender-specific weight formula.  Fetal Diagn Ther. 2008;  24 321-326
• 29 Deter R L, Hadlock F P. Use of ultrasound in the detection of macrosomia: a review.  J Clin Ultrasound. 1985;  13 519-524
• 30 Coomarasamy A, Connock M, Thornton J et al. Accuracy of ultrasound biometry in the prediction of macrosomia: a systematic quantitative review.  BJOG. 2005;  112 1461-1466
• 31 Loetworawanit R, Chittacharoen A, Sututvoravut S. Intrapartum fetal abdominal circumference by ultrasonography for predicting fetal macrosomia.  J Med Assoc Thai. 2006;  89 S60-S64
• 32 Henrichs C, Magann E F, Brantley K L et al. Detecting fetal macrosomia with abdominal circumference alone.  J Reprod Med. 2003;  48 339-342
• 33 Maticot-Baptista D, Collin A, Martin A et al. Prevention of shoulder dystocia by an ultrasound selection at the beginning of labour of foetuses with large abdominal circumference.  J Gynecol Obstet Biol Reprod. 2007;  36 42-49
• 34 Sacks D A, Chen W. Estimating fetal weight in the management of macrosomia.  Obstet Gynecol Surv. 2000;  55 229-239
• 35 Neiger R. Fetal macrosomia in the diabetic patient.  Clin Obstet Gynecol. 1992;  35 138-150
• 36 Zimmer E Z, Divon M Y. Sonographic diagnosis of IUGR-macrosomia.  Clin Obstet Gynecol. 1992;  35 172-184
• 37 Mongelli M, Gardosi J. Gestation-adjusted projection of estimated fetal weight.  Acta Obstet Gynecol Scand. 1996;  75 28-31