Detection of structural abnormalities in fetuses with normal karyotype at 11-13 weeks using the anatomic examination protocol of the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG).

Objective

To assess the performance of sonography in the detection of fetal nonchromosomal abnormalities using a standard anatomic examination protocol proposed by International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) at 11+0-13+6 weeks.Materials and methods: A prospective observational study was conducted between June 2013-May 2017 in singleton pregnancies attending for a routine scan at 11+0-13+6 weeks. All examinations were performed by maternal-fetal medicine specialists certified by the Fetal Medicine Foundation according to the anatomic examination protocol described in the ISUOG guidelines. First-trimester findings were compared to those of the anomaly scan at 20+0-23+6 weeks and the postnatal examination. The primary outcome was the detection rate of major structural abnormalities in fetuses with normal karyotype at 11+0-13+6 weeks.

Results

After excluding 17 chromosomal abnormalities, major fetal structural defects were detected in 57 (1.7%) of the remaining 3361 cases. Of these, 27 (47.3%) were detected at 11+0-13+6 weeks, including all cases of acrania (4), exomphalos (4), megacystis (2) and body stalk anomaly (2). Furthermore, there was a first-trimester diagnosis in 36.4% (4/11) of major cardiac defects, 38% (6/16) of limb defects, and 100% (2/2) of facial clefts.Discussion: Targeted ultrasound examination may identify all the so called "always" detectable major abnormalities and a significant proportion of the "sometimes", detectable at 11+0-13+6 weeks.