The objective of this study is to analyze the prenatal management and prognostic factors of hygroma colli cysticum by using cytogenetic tests and sonographic morphological features. All cases with hygroma colli cysticum diagnosed and managed at our Prenatal Diagnostics Unit between January 96 and September 2000 were analyzed. Sonographic morphological features were divided in two groups; nonseptated (n = 18) and septated (n = 12) hygroma colli cysticum lesions were compared with fetal karyotype results and pregnancy outcome data. Statistical analysis was performed by Chi-square test and statistical significance was defined as p <0.05. In 5 years, 30 cases with hygroma colli cysticum were identified. Cytogenetic results were obtained from 23 (76.7%) cases (four chorionic villus sampling and 19 amniocentesis). Chromosomal abnormalities were present in 13 cases (56.5%). The most common chromosomal abnormality was Turner Syndrome (four cases, 17.4%) and Trisomy 18 (four cases, 17.4%). Pregnancy outcome data were available for 29 patients. Those fetuses with septated hygroma colli cysticum tended to have a worse fetal outcome, without statistical significance (p >0.05), compared with the nonseptated hygroma colli cysticum cases (75 vs. 61.1%, respectively). Fetal hygroma colli cysticum, either septated or not, carries high risks of aneuploidies and adverse fetal outcome. Recommended management includes karyotyping and if parents decide to continue the pregnancy ultrasound scan at 20 to 22 weeks' gestation is necessary, for excluding associated anomalies. At birth, if the cystic hygroma persists, it should be noted that a respiratory difficulty can happen and a pediatrician should standby as a precaution.