Three- and 4-Dimensional Ultrasonography in the Prenatal Evaluation of Fetal Anomalies Associated With Trisomy 18

Abstract

Objective. The purpose of this study was to assess the usefulness of 3-and 4-dimensional ultrasonography (3D/4DUS) for the description of anomalies associated with trisomy 18 and to determine whether 3D/4DUS adds diagnostic information over what is provided by conventional 2-dimensional ultrasonography (2DUS) alone. Methods. Twenty-six fetuses subsequently proven to have trisomy 18 underwent prenatal ultrasonographic evaluations by both 2DUS and 3D/4DUS. Volume data sets were acquired by the same sonographers after the conventional 2DUS examinations and were explored with 4-dimensional imaging software by another independent examiner blinded to the indications of 2DUS. The findings detected by 2DUS and 3D/4DUS were compared with those acquired at autopsy. The sensitivity of each modality for detecting anomalies was calculated and compared by the McNemar test. Results. Excluding polyhydramnios, there were 131 anomalies confirmed postnatally in 26 fetuses with trisomy 18. There was a statistically significant difference in the sensitivity for detecting anomalies between 3D/4DUS and 2DUS (93.89% versus 73.28%; McNemar value = 23.31; P < .05), especially in anomalies of the face/neck (96.15% versus 65.38%; McNemar value = 6.13; P < .05) and extremities (96.3% versus 48.15%; McNemar value = 11.07; P < .05). Three-and 4-dimensional ultrasonography provided additional diagnostic information for 83.97% of the anomalies related to trisomy 18 and influenced the obstetric management of 4 fetuses. Conclusions. Three-and 4-dimensional ultrasonography offered diagnostic advantages for many anomalies associated with trisomy 18, especially for anomalies of the extremities and face. This modality could be a powerful adjunct to 2DUS in the prenatal anatomic evaluation of fetuses with trisomy 18.

Diagnosis of Fetal Limb Abnormalities Before 15 Weeks

“…25,36 Although the potential utility of 3D sonography is broad, prior studies have shown it to be particularly useful for the depiction of certain structures, including fetal limbs. 11,24,26,29,37,38 Sepulveda et al 39 reported a 6% firsttrimester detection rate of abnormal hand posturing in their case series of 55 fetuses with trisomy 18, specifically noting the possibility of 3D sonography improving this low detection rate. Although 3D sonography was only considered useful in 3 of the 9 cases in which it was performed in this study, its utility in characterizing defects and explaining anomalies to parents was considered essential in each of these cases (Figures 1 and 3).…”

“…Three‐dimensional depiction of the developing fetus has also been shown to be more comprehensible to lay people, which can be useful when counseling parents about detected anomalies 25 , 36 . Although the potential utility of 3D sonography is broad, prior studies have shown it to be particularly useful for the depiction of certain structures, including fetal limbs 11 , 24 , 26 , 29 , 37 , 38 . Sepulveda et al 39 reported a 6% first‐trimester detection rate of abnormal hand posturing in their case series of 55 fetuses with trisomy 18, specifically noting the possibility of 3D sonography improving this low detection rate.…”

“…The frequency of cases with trisomy 18 in our study (9 of 15) warrants a more thorough discussion of this common aneuploidy. Trisomy 18 is a usually lethal chromosomal disorder that affects approximately 1 per 6000 live births 38 . The exact incidence of trisomy 18 at conception is unknown because approximately 95% of affected fetuses are spontaneously aborted during gestation, whereas more than 90% of those that are carried to term die in their first year of life 8 (including one‐third during the first day of life 38 ).…”

“…Trisomy 18 is a usually lethal chromosomal disorder that affects approximately 1 per 6000 live births 38 . The exact incidence of trisomy 18 at conception is unknown because approximately 95% of affected fetuses are spontaneously aborted during gestation, whereas more than 90% of those that are carried to term die in their first year of life 8 (including one‐third during the first day of life 38 ). It is the most common trisomy presenting with limb abnormalities and accounts for 59% to 88% of all aneuploidies in fetuses with prenatally diagnosed limb abnormalities 13 , 37 , 40 .…”

“…The limb defects associated with trisomy 18 are diverse and commonly include clenched hands with overlapping digits, radial aplasia or shortening, ulnar shortening, clinodactyly or syndactlyly, short humeri, absence or hypoplasia of the first metacarpal and thumb, and rocker bottom feet (Figures 1, 2, and 6). 8 , 9 , 38 , 46 …”