Ultrasonographic diagnosis of trisomy 18: is it practical in the early second trimester?

Abstract

The objective of this paper was to determine the rate of prenatal detection of ultrasonographic abnormalities in fetuses with trisomy 18 during the early second trimester. Our prenatal diagnosis database (encompassing January 1987 to June 1996) was searched for all patients referred for prenatal genetic evaluation between 14 and 22 weeks of gestation and who were found to have a fetus with a trisomy 18 karyotype. The sonographic reports and films were evaluated for the presence or absence of fetal anatomic abnormalities. Thirty-five fetuses were identified with a mean age of 17.3+/-2.0 (standard deviation) weeks. Thirty of the 35 (86%) had at least one detected abnormality. Most fetuses had more than one abnormality, with the mean number of abnormalities per fetus being three (range, 0 to 6). The most common abnormalities noted were persistent abnormal position of fetal fingers (89%); choroid plexus cysts (43%); abnormally shaped fetal head (strawberry or lemon) (43%); two-vessel umbilical cord (40%); cardiac defects (37%); intrauterine growth restriction (29%); omphalocele (20%); neural tube defects (9%); and cystic hygroma or lymphangiectasia (14%). Abnormalities of amniotic fluid volume (12%) and renal defects (9%) were seen less frequently. These data suggest that in the early second trimester, the time of most routine screening ultrasonographic examinations, most but not all fetuses with trisomy 18 have sonographically detectable anatomic abnormalities. The fetal hand appears to be abnormal in most early second trimester fetuses with trisomy 18, but the abnormality may be subtle and or unilateral.

Second-Trimester Sonography and Trisomy 18

“…Previously published reports detailing the sonographic findings with trisomy 18 show that, although choroid plexus cysts are seen frequently, most are present with other sonographic findings. [5][6][7][8][9][10][11][12][13] In the 223 fetuses from these combined series that had second-trimester sonograms, isolated choroid plexus cysts were not a common finding (6.7%).…”

“…They are seen in up to half of second-trimester fetuses and are often found with other anomalies. [3][4][5][6][7][8][9][10][11][12][13] In the nearly 2 decades since the initial report by Chudleigh et al, 1 a large volume of literature has been published regarding the sonographic detection of choroid plexus cysts in the second trimester. Despite this, a consensus of opinion has yet to be reached on the genetic significance and appropriate management when these cysts are detected as an isolated finding.…”

Prenatal Detection of Fetal Trisomy 18 Through Abnormal Sonographic Features

“…Three of the fetuses had no sonographic findings at all; however, these examinations were performed between 16 and 17 weeks. 13 In examining fetuses with trisomy 18 during the early second trimester only, Shields et al 4 found that most, but not all (86%; 30 of 35) fetuses had 1 or more detected abnormalities on sonography, with a mean number of abnormalities per fetus of 3 (range, 0-6). Salihu et al 6 found that of their 11 cases of trisomy 18, only 64% had prenatally detected sonographic anomalies, with polyhydramnios (n = 4) being the most commonly seen abnormality.…”

“…Only 2 studies provided descriptions about the content of the sonographic examinations in detecting trisomy 18. 4,7 In addition, all previous studies have found that 64% to 97% of fetuses with trisomy 18 have 1 or more detectable abnormalities on sonography.…”

“…[1][2][3][4] There are several studies that have described the types and frequencies of prenatal sonographic findings in fetuses with trisomy 18. [2][3][4][5][6] However, in most studies, descriptions of the normal content and detail of their routine prenatal sonographic examinations were not provided. Only 2 studies provided descriptions about the content of the sonographic examinations in detecting trisomy 18.…”