Sonographic Weight Estimation in Fetuses with Congenital Diaphragmatic Hernia

Abstract

Purpose: To determine the accuracy of sonographic weight estimation (WE) for fetuses with congenital diaphragmatic hernia (CDH), and to assess whether certain sonographic models perform better than others in cases of CDH.

Material and Methods: In a retrospective, multicenter cohort study, the accuracy of WE in fetuses with CDH (n = 172) was evaluated using eight sonographic models and was compared with a control group of fetuses without malformations (n = 172). Each fetus underwent ultrasound examination with complete biometric parameters within 7 days of delivery. The accuracy of the different formulas was compared using means of percentage errors (MPE), medians of absolute percentage errors (MAPE), and proportions of estimates within 10 % of actual birth weight.

Results: Fetuses with CDH had a significantly lower abdominal circumference (AC) in comparison with the control group (293.6 vs. 312.0 mm, p < 0.001). All of the formulas tested in fetuses with CDH, except for the Siemer equation (the only model that does not incorporate any abdominal measurements), showed significantly lower (more negative) MPEs, larger MAPEs, and smaller proportions of estimates within 10 % of actual birth weight in comparison with the control group. 

Conclusion: The accuracy of sonographic WE in fetuses with CDH is significantly poorer than in fetuses without malformations, principally because of a larger systematic error due to artificially small AC measurements. The development of new, specific models derived from fetuses with CDH could improve the accuracy of WE for infants with this condition.

Zusammenfassung

Ziel: Ziel dieser Studie war der Vergleich der Genauigkeit der sonografischen Gewichtsschätzung bei Feten mit Zwerchfelldefekten (CDH) mit einer Kontrollgruppe von Feten ohne Auffälligkeiten.

Material und Methoden: Die Genauigkeit der sonografischen Gewichtsschätzung wurde in einer retrospektiven multizentrischen Studie in einer Gruppe von 172 Feten mit CDH mittels 8 verschiedener Gewichtsschätzungsformeln erhoben und direkt mit einer Kontrollgruppe von Feten ohne Auffälligkeiten verglichen. Der Zeitabstand zwischen der vollständig durchgeführten Biometrie und der Entbindung lag bei allen Feten unter 8 Tagen. Um die Genauigkeit der verschiedenen Formeln zu testen und zu vergleichen, wurden folgende Parameter berechnet: mittlerer prozentualer Fehler (MPE), Median des absoluten Fehlers (MAPE) und Prozentsatz an Gewichtsschätzungen innerhalb von 10 % des tatsächlichen Geburtsgewichts.

Ergebnisse: Feten mit CDH hatten signifikant niedrigere Abdomenumfänge (AU) im Vergleich mit der Kontrollgruppe (293,6 vs. 312,0 mm, p < 0,001). Mit Ausnahme der Siemer Formel (das einzige Modell, das nicht den Abdomenumfang berücksichtigt), zeigten alle getesteten Formeln in der CDH Gruppe signifikant niedrigere (negativere) MPEs, höhere MAPEs und einen kleineren Prozentsatz an Schätzungen innerhalb von 10 % des tatsächlichen Geburtsgewichts.

Schlussfolgerung: Die Genauigkeit der fetalen Gewichtsschätzung bei Feten mit CDH ist im Vergleich zu Feten ohne Auffälligkeiten signifikant schlechter. Hauptgrund hierfür ist ein größerer systematischer Fehler wegen der kleineren Abdomenumfangsmessungen. Die Entwicklung von neuen, speziellen Formeln für Feten mit CDH könnte die Genauigkeit der Gewichtsschätzung erhöhen.

Key words

fetus - hernia - ultrasound

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