Cystic Hygroma
Abstract & Commentary
By John C. Hobbins, MD, Professor of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora, Colorado, is Associate Editor for OB/GYN Clinical Alert.
Dr. Hobbins reports no financial relationships relevant to this field of study.
Synopsis: Even with emerging maternal DNA testing, first trimester fetal ultrasound continues to offer benefit in the detection of cystic hygroma, which was found to be associated with an adverse fetal outcome in 86% of pregnancies identified.
Source: Scholl J, et al. First-trimester cystic hygroma: Relationship of nuchal translucency thickness and outcomes. Obstet Gynecol 2012;120:551-559.
The emergence of maternal DNA testing for fetal an-euploidies has necessitated a rethinking of our standard screening protocols. With reasonable accuracy, a single blood test can now rule out fetal trisomy 21, 18, and 13, in addition to sex chromosome abnormalities such as Turner syndrome. However, nuchal translucency (NT) testing, the staple of current screening protocols, will remain an essential adjunctive tool because, as noted below, it will continue to identify pregnancies at risk for chromosomal or non-chromosomal abnormalities not detected by current maternal serum DNA tests.
A group of investigators focused on one particularly ominous first trimester finding — cystic hygroma (CH). They culled data over a 10-year period from five centers in the Northeast. Their ultrasound definition of CH was "a large hypoechoic space on the back of the neck extending along the length of the back, containing septations." A total of 944 fetuses were labeled as having CH. Of the 729 cases where fetal diagnostic data were available, 400 (54.9%) had abnormal karyotypes. A major structural anomaly emerged in 61 of 212 with normal karyotypes (29%) and perinatal loss occurred in 115 of the 229 pregnancies not terminated (39%). Lumped together, 86.6% of pregnancies ended in adverse outcome.
After adjusting for confounding variables, for every millimeter of increase in NT diameter there was a rise in abnormal karyotype of 44%, a congenital anomaly increase of 26%, and an increase in perinatal loss of 47%. Interestingly, in those with normal karyotypes, only 2.5% had fetal anomalies that were not detected by ultrasound.
Commentary
For every 280 pregnancies, one will be complicated by fetal CH. Since NT screening is being performed more frequently in the offices of OB/GYN generalists, some preliminary point-of-entry counseling may be required when CHs are first encountered. Formal genetic counseling and diagnostic invasive procedures (i.e., chorionic villus sampling or amniocentesis) will likely continue to be offered in referral centers. However, in many settings, waiting for a more definitive answer might leave the patient in emotional limbo for days. Couples with a fetus diagnosed with a CH will be pressing for at least a ballpark estimate of their risks of the above adverse outcomes. This study now has some of the best data available regarding the chances of having a fetus with a chromosome abnormality (55%), a fetal structural abnormality (29%), or perinatal death (39%). However, despite these gloomy statistics, the study has shown that after pregnancy terminations were excluded, almost 60% of the 180 continuing pregnancies had normal appearing fetuses at the time of birth.
I chose this CH paper to review because the diagnosis should not be difficult for someone trained in NT exams (and those offering this test should not be doing these exams if they are not capable of interpreting the ultrasound results). Yes, the nuances involved in first trimester screening often can be difficult to deal with, but CH should represent a category where a provider should be able to counsel patients initially regarding its implications.
The emergence of maternal DNA testing for fetal an-euploidies has necessitated a rethinking of our standard screening protocols. With reasonable accuracy, a single blood test can now rule out fetal trisomy 21, 18, and 13, in addition to sex chromosome abnormalities such as Turner syndrome.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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