(716) Outcomes from a 15 Year Review of Cystic Hygroma

Objective: Invasive genetic testing is routinely recommended to investigate aneuploidy as a cause of cystic hygroma in the first trimester. In the context of normal genetic testing, the predicted outcome is impacted by the presence of co-existing structural anomalies, particularly cardiac anomalies. We reviewed the diagnosis and outcome of these patients to establish contemporary outcome data to aid appropriate counseling.

Study Design: This is a retrospective cohort study in a single large maternity hospital. Cases were identified using a fetal anomaly database and an electronic health record system. Data were collected on all patients with a fetal diagnosis of a nuchal translucency > 3mm with septations from 2007 to 2022. Results of chromosomal analysis, pregnancy outcomes and fetal outcomes were collated and described using summary statistics.

Results: During the 15-year period, there were over 135,000 deliveries at our center. 677 cases of septated cystic hygroma were diagnosed. Pregnancy outcome was obtained in 97.5% (n=660) of cases, with 92% (621/677) undergoing invasive prenatal or postnatal testing. 39% (247/621) had a normal karyotype. 38% (249/660) of women underwent termination of pregnancy.  In-utero demise occurred in 24% (159/660). Structural anomalies were found in 16% (39/247) of those with normal karyotype.  In cases of cystic hygroma, normal invasive testing in the absence of structural anomalies carried a livebirth rate of 86% (164/191), in contrast to an overall livebirth rate of 38% (252/660) in all pregnancies affected by cystic hygroma.

Conclusion: Cystic hygroma is a significant finding in early pregnancy which confers a risk of aneuploidy of approximately 60% and is associated with adverse pregnancy outcomes. Outcomes of the study demonstrate a high livebirth rate in those with normal invasive testing and fetal echocardiography. This confirms the significance of appropriate counseling regarding confirmatory invasive testing, and highlights the value of follow-up with detailed anatomy ultrasound.