Is a Routine Ultrasound in the Third Trimester Justified? – Additional Fetal Anomalies Diagnosed After Two Previous Unremarkable Ultrasound Examinations

Zusammenfassung

Ziel: Die Detektion fetaler Fehlbildungen gehört zur Routine in der Schwangerenvorsorge. In Europa variieren die Richtlinien bezüglich Zeitpunkt und Anzahl der Untersuchungen. Ein Fehlbildungsultraschall im 3. Trimenon erscheint aus mehreren Gründen sinnvoll. Einige fetale Anomalien können sich erst im Verlauf der Schwangerschaft entwickeln oder sind erst später erkennbar. Ziel dieser Studie war, die Anzahl unentdeckter Fehlbildungen im 3. Trimenon zu analysieren. Material und Methoden: Von 1998 – 2008 erfolgte bei 8074 Feten eine Ultraschalluntersuchung zwischen 11 – 14 Schwangerschaftswochen (SSW). Bei 79 % (6378 / 8074) wurde der Fehlbildungsultraschall zwischen 20 – 24 SSW durchgeführt. Wenn bei beiden Untersuchungen keine fetalen Fehlbildungen vorlagen, wurden sie in die Studie aufgenommen und erhielten einen weiteren Ultraschall zwischen 28 – 32 SSW (n = 5044). Ausgewertet wurden die neu entdeckten strukturellen Fehlbildungen im 3. Trimenon. Ein Outcome war bei 96 % verfügbar. Ergebnisse: Die Inzidenz fetaler Fehlbildungen lag bei 3,6 % (n = 289), 40 % (116 / 289) wurden zwischen 11 – 14 SSW detektiert. Im 2. Trimenon wurden 35 % (n = 102) zusätzliche fetale Fehlbildungen entdeckt. In 3. Trimenon wurden 15 % (n = 44) der strukturellen Fehlbildungen detektiert. Dies waren insbesondere Befunde des Urogenitaltrakts (n = 18), gefolgt von Herzfehlern (n = 9), Anomalien des Gastrointestinaltrakts (n = 6) und des zentralen Nervensystems (n = 4). Bei einem Feten handelte es sich um eine vorher unentdeckte Chromosomenstörung. Schlussfolgerung: Die sonografische Untersuchung im 3. Trimenon erhöht pränatal die Detektionsrate von fetalen Fehlbildungen. Dies ist für das perinatale Management und postnatale Follow-up von Relevanz.

Abstract

Purpose: The detection of fetal structural abnormalities is a routine part of antenatal care. Ultrasound examination policies vary among European countries. An additional ultrasound for fetal structural anomalies in the 3 rd trimester seems important for many reasons. Some abnormalities develop or first become apparent later in pregnancy. The aim of the study was to analyze the rate of previously undetected structural abnormalities in the 3 rd trimester. Materials and Methods: 8074 fetuses were examined in this prospective study between 1998 and 2008. All received an examination at 11 – 14 weeks and 79 % (6378 / 8074) of these fetuses also received an ultrasound at 20 – 24 weeks. If both of the examinations did not detect structural abnormalities, the fetuses were included in the study group and received an ultrasound at 28 – 32 weeks (n = 5044). New structural abnormalities in the 3 rd trimester were analyzed. The outcome was available in 96 % of the cases. Results: The overall incidence of fetal malformations was 3.6 % (n = 289), of which 40 % (116 / 289) were diagnosed at 11 – 14 weeks. The following 2nd trimester scan revealed 102 (35 %) new fetal malformations. An additional 44 (15 %) structural abnormalities were found in the 3 rd trimester. These were mainly abnormalities of the urogenital system (n = 18). There were also anomalies of the cardiovascular system (n = 9), the gastrointestinal system (n = 6) and the central nervous system (n = 4). One of the cases had a previously undiagnosed abnormal karyotype. Conclusion: The ultrasound examination in the 3 rd trimester is of additional benefit and can detect previously unknown structural abnormalities. These findings are relevant for perinatal management and postnatal follow-up.

Key words

fetal anomalies - third trimester - detection rate - screening ultrasound

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