Objective: Our purpose was to determine the specific likelihood of different aneuploidies by gestational age in patients with nuchal folds and simple and septated nuchal membranes.
Study design: Retrospective database analysis was performed of 158 consecutive patients with a nuchal fold or simple or septated nuchal membrane on either abdominal or vaginal ultrasonography.
Results: Thirty-eight patients with nuchal folds, 65 with simple nuchal membranes, and 55 with septated nuchal membranes were evaluated. Septated nuchal membranes were associated with the highest incidence of karyotypic abnormalities (> 50%). A peak incidence of trisomy 21 (27%) was found in the early midtrimester, leveling off to 11% by the late midtrimester. The late first trimester had a high incidence of trisomy 18 (22%), occurring more frequently than 45,X.
Conclusion: Ultrasonographic anomalies in the posterior neck are associated with aneuploidy from 21% to 58% of the patients in this selected population. Each anomaly has different risks for aneuploidy type, varying with gestational age at diagnosis.