Prenatal diagnosis of isolated abnormal number of ribs

Authors

  • R. Hershkovitz

    Corresponding author
    1. Ultrasound Unit, Department of Obstetrics and Gynecology, Soroka University Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
    • Ultrasound Unit, Department of Obstetrics and Gynecology, Soroka University Medical Center, POB 151, Beer-Sheva 84101, Israel
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Abstract

Objective

To determine the incidence of prenatal isolated abnormal number of ribs, using three-dimensional (3D) ultrasound.

Methods

This was a prospective study of low-risk women with singleton pregnancy and normal fetal anatomy scan. 3D examinations of the fetal ribs were carried out at the time of the routine anomaly scan at 14–16 or 20–24 weeks of gestation. A 3D volume of the spine was acquired with a mechanical sweep that lasted between 2 and 4 s per volume and was performed when the fetus had a minimally flexed head position. Fetal ribs were reviewed on the rendered image (maximal mode), both while the patient was in the clinic and again later.

Results

Three hundred and sixty-seven pregnant women were evaluated. Twenty-three (6.3%) fetuses were found to have an abnormal number of ribs. Fifteen (4.1%) had 11 ribs unilaterally, with the last (12th) rib missing. One patient (0.27%) had 13 ribs unilaterally (with a small extra rib after the last rib). Two (0.5%) patients had 13 ribs bilaterally with an extra rib after the 12th rib on each side and two (0.5%) patients had 13 ribs bilaterally with an extra cervical rib on each side. Three (0.8%) patients had an extra unilateral cervical rib. In all, 1.4% of patients had extra cervical ribs.

Conclusions

The incidence of abnormal number of ribs in this normal population was 6.3%. When isolated, this finding is a normal variant. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.

Ancillary