Cystic hygroma prevalence underappreciated: Found in 1 in 300 pregnancies at 10-14 weeks

OB/GYN News, March 15, 2002 by Nancy Walsh

NEW ORLEANS -- First-trimester cystic hygroma is considerably more common in the general population than has been appreciated, Dr. Fergal D. Malone said at the annual meeting of the Society for Maternal-Fetal Medicine.

This condition, which is characterized ultrasonographically by an enlarged hypoechoic space at the back of the fetal neck and visible septations, is present in approximately 1 in 300 pregnancies at 1014 weeks' gestation, according to the first prospective data analyzing its prevalence in an unselected population.

And unlike third-trimester cystic hygroma, first-trimester cystic hygroma is strongly associated with a range of structural and chromosomal abnormalities.

"The overall prognosis for this condition is poor," Dr. Malone said. "Fewer than one in four cases of first-trimester cystic hygroma will result in normal neonatal outcome. We hope these data, the first to demonstrate prevalence and natural history of this condition, will be helpful to you in counseling patients."

In a subanalysis from the First And Second Trimester Evaluation of Risk (FASTER) trial, in which thus far 26,966 patients have had ultrasound nuchal translucency screening, 81 cases of first-trimester cystic hygroma have been identified for a rate of 1 in 333 or 0.3%, said Dr. Malone of the division of maternal-fetal medicine, Columbia Presbyterian Medical Center, New York.

Previous estimates ranged from 1 in 1,000 to 1 in 12,000. Accurate knowledge about cystic hygroma has been hampered in the past by the fact that most data were collected from tertiary referral centers and do not reflect the wider population, he explained.

Among the 81 cases in this series, two were lost to follow-up. Of the remaining 79, karyotyping was performed in 63; 34 (54%) were abnormal. Twelve of these were found to have Down syndrome, eight had Turner's syndrome, and seven had trisomy 18. An additional three had trisomy 13, three had triploidy, and one case involved a mosaic deletion of chromosome 8.

Elective termination was chosen in 26 of the 34 cases of aneuploidy (76%). Spontaneous demise occurred in 7 (21%). "There was only one live birth at term, of an infant with Turner's syndrome," Dr. Malone said at the meeting, which was cosponsored by the American College of Obstetricians and Gynecologists.

Karyotype was not classified as abnormal in 45 cases, 29 in which karyotyping was done and confirmed to be normal and an additional 16 in which karyotyping was not performed.

There were major structural malformations in 14 of these cases, including skeletal dysplasias, hypoplastic left heart, multiple pterygium, and pleural effusion requiring an in utero shunt.

Among the 29 confirmed euploid fetuses, 12 had a normal outcome. Elective termination was chosen in another 12 cases. There was one case of an intrauterine demise, but there also were seven spontaneous intrauterine resolutions at a mean gestation of 19 weeks, Dr. Malone reported.

Of the 16 in which karyotype was unknown, 6 had a normal outcome. Additionally, there were four cases of intrauterine demise and seven spontaneous resolutions of the condition at a mean gestation of 17 weeks. There also were five elective terminations.

Longer-term surveillance of these patients will continue to follow pediatric development, he said.

The FASTER trial is a national study evaluating a number of screening tests for trisomy 21, as well as other fetal abnormalities.