Objective: To estimate prevalence, natural history, and outcome of septated cystic hygroma in the first trimester in the general obstetric population, and to differentiate this finding from simple increased nuchal translucency.
Methods: Patients at 10.3-13.6 weeks of gestation underwent nuchal translucency sonography as part of a multicenter clinical trial. Septated cystic hygroma cases were offered chorionic villi sampling for karyotype, and targeted fetal anatomical and cardiac evaluations. Survivors were followed up for fetal and long-term pediatric outcome (median 25 months, range 12-50 months). Cases of septated cystic hygroma were also compared with cases of simple increased nuchal translucency.
Results: There were 134 cases of cystic hygroma (2 lost to follow-up) among 38,167 screened patients (1 in 285). Chromosomal abnormalities were diagnosed in 67 (51%), including 25 trisomy-21, 19 Turner syndrome, 13 trisomy-18, and 10 others. Major structural fetal malformations (primarily cardiac and skeletal) were diagnosed in 22 of the remaining 65 cases (34%). There were 5 cases (8%) of fetal death and 15 cases of elective pregnancy termination without evidence of abnormality. One of 23 (4%) normal survivors was diagnosed with cerebral palsy and developmental delay. Overall, survival with normal pediatric outcome was confirmed in 17% of cases (22 of 132). Compared with simple increased nuchal translucency, cystic hygroma has 5-fold, 12-fold, and 6-fold increased risk of aneuploidy, cardiac malformation, and perinatal death, respectively.
Conclusion: First-trimester cystic hygroma was a frequent finding in a general obstetric screening program. It has the strongest prenatal association with aneuploidy described to date, with significantly worse outcome compared with simple increased nuchal translucency. Most pregnancies with normal evaluation at the completion of the second trimester resulted in a healthy infant with a normal pediatric outcome.