First-trimester sonographic findings in trisomy 18: a review of 53 cases.

OBJECTIVE

To report our experience with first-trimester sonographic findings in pregnancies complicated by trisomy 18.

METHODS

Proven cases of trisomy 18 undergoing sonographic examination between 11 + 0 and 13 + 6 weeks of gestation were retrospectively identified. Information on maternal demographics, prenatal sonographic findings, and chromosomal analysis results was obtained by reviewing the ultrasound reports and medical records.

RESULTS

During the 12-year period from July 1997 to June 2009, 53 cases of full trisomy 18 had first-trimester sonographic examination performed at our institution. All but one fetus displayed one or more abnormal sonographic finding, most commonly increased nuchal translucency thickness (n = 48, 91%). Absent or hypoplastic nasal bone was documented in 53% of the fetuses in which this marker was specifically looked for. Structural anomalies included omphalocele in 11 (21%), abnormal posturing of the hands in three (6%), megacystis in two (4%), and abnormal four-chamber view of the heart in two (4%). Early-onset fetal growth restriction and bradycardia were documented in 14 (26%) and 4 (8%) of the cases, respectively.

CONCLUSIONS

Our study demonstrates that a large number of fetuses with trisomy 18 have abnormal sonographic findings in the first trimester. However, the sonographic features usually found in the second-trimester are difficult to detect at an early gestational age. The recognition of the specific first-trimester sonographic pattern of trisomy 18 may allow improved detection of this serious condition in early pregnancy.