Ultraschall Med 2020; 41(04): 410-417
DOI: 10.1055/a-0591-3206
Original Article
© Georg Thieme Verlag KG Stuttgart · New York

Comparison of Current Swiss Fetal Biometry Reference Charts with Reference Charts from 1999. Are Fetuses Getting Bigger?

Vergleich aktueller fetaler Referenzkurven mit Referenzkurven aus dem Jahr 1999. Werden Feten immer grösser?
Johannes Knitza
1   Clinic of Internal Medicine 3, University Hospital Erlangen, Germany
,
Juozas Kurmanavicius
2   Clinic of Obstetrics, University Hospital Zurich, Switzerland
,
Florian Faschingbauer
3   Clinic of OB/GYN, University Hospital Erlangen, Germany
,
Josef Wisser
2   Clinic of Obstetrics, University Hospital Zurich, Switzerland
› Author Affiliations
Further Information

Publication History

25 October 2017

28 February 2018

Publication Date:
24 May 2018 (online)

Abstract

Purpose To create current fetal biometry reference ranges and to compare them with references published in 1999, from the same local area in order to generate data for secular trend in fetal size.

Materials and Methods Applying the same methodology as previously published, we calculated reference ranges for biparietal diameter (BPD), occipitofrontal diameter (OFD), head circumference (HC), abdominal circumference (AC) and femur length (FL) in 7863 patients examined at the obstetric clinics in a cross-sectional, prospective study in a university setting from January 2008 to December 2014. In order to compare the new reference ranges with our previously published data, we used Z-Scores and displayed the pick-up of fetal biometry data below the 5th and above the 95th percentile using the previously published reference charts.

Results The comparison of the charts showed a minimal but clinically relevant increase in mean fetal body measures (BPD, HC, AC). Applying the 1999 charts to the new dataset, we would classify only 162 of 339 fetuses (47.8 %) to be correctly below the 5th percentile for AC and only 134 of 349 (38.4 %) fetuses were correctly below the 5th percentile for HC. On the other hand, the 1999 charts classified 426 instead of 332 fetuses to be above the 95th percentile for AC, which means an overestimation of 28.3 %.

Conclusion Applying a similar methodology, study collective and clinical setting, our new charts showed clinically relevant differences compared to the 1999 charts. The data suggest that within one generation fetuses are getting bigger and regular updates of fetal reference charts are needed.

Zusammenfassung

Ziel In der Arbeit werden aktuelle Referenzwerte der fetalen Biometrie generiert und diese mit den 1999 publizierten Referenzwerten verglichen. Beide Datensätze wurden an der gleichen Institution erhoben, um Daten für eine Einschätzung eines Langzeittrends zu erhalten.

Material und Methoden In einer prospektiven Querschnittsstudie wurden Ultraschallmessungen von 7863 Einlingsschwangerschaften zwischen Januar 2008 und Dezember 2014 in einem universitären Perinatalzentrum durchgeführt. Um Vergleichbarkeit herzustellen, wurden die Referenzwerte nach der 1999 publizierten Methodik kalkuliert. Die biometrischen Referenzwerte für biparietalen Durchmesser (BPD), okzipitofrontalen Durchmesser (OFD), Kopfumfang (HC), Abdomenumfang (AC) und Femurlänge (FL) wurden berechnet. Zum Vergleich der aktuellen Referenzwerte mit den publizierten Kurven wurden Z-Scores erstellt und die Detektion fetaler biometrischer Daten unter der 5. und über der 95. Perzentile unter Verwendung der publizierten Referenzkurven berechnet.

Ergebnisse Der Vergleich der alten und neuen Referenzwerte ergab einen Anstieg der durchschnittlichen fetalen Körpermaße (BPD, HC, AC). Verwendet man anstelle der aktuellen Referenzwerte die 1999 publizierten Kurven, erkennt man nur 162 statt 339 Feten (47,8 %) unter der 5. Perzentile für AC und 134 statt 349 (38,4 %) Feten unter der 5. Perzentile für HC. Andererseits führt die Verwendung der alten Referenzwerte in 426 statt 332 Feten (28,3 %) die über der 95. Perzentile für den AC liegen zur einer vermeintlichen Überschätzung.

Schlussfolgerung Mittels gleicher Methodik, vergleichbaren Studienkollektivs und klinischen Bedingungen konnten neue Referenzwerte generiert werden, die klinisch relevante Unterschiede im Vergleich zu den alten Referenzwerten zeigten. Unsere Daten legen den Verdacht nahe, dass Feten innerhalb einer Generation größer werden und regelmäßige Updates von Referenzwerten notwendig sind.

 
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