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47,XYY karyotype occurs in 1 out of 1,000 male births. Physical phenotype is normal, with tall stature by adolescence. Prenatal diagnosis of the 47,XYY syndrome is usually fortuitous. Some cases are being diagnosed when prenatal karyotyping is done for the detection of Down syndrome and other major aneuploidies. Some cases are diagnosed when prenatal ultrasonographic findings of fetal abnormalities are found. Herein, we report a case of 47,XYY after prenatal finding of fetal cystic hygroma with spontaneous resolution.A 19-year-old primigravid woman presented for antenatal care at the 13th week of pregnancy. She used oral isotretinoin, being unaware of pregnancy, for a treatment of acne during the first 4 weeks of gestation. Ultrasonogram was performed due to first trimester screening and the history of isotretinoin exposure. The result revealed a single viable fetus compatible with a 13-week pregnancy and a posterior cervical cystic hygroma. No other structural anomalies were noted. An amniocentesis was performed for prenatal chromosome analysis and a 47,XYY karyotype was found. Repeated ultrasonogram at 23-week gestation showed that the cystic hygroma had spontaneously disappeared. She delivered a normal appearing male infant by spontaneous vaginal delivery at 40 weeks. The maternal and neonatal outcomes were uneventful.Fetal cystic hygroma can be associated with abnormal karyotype, such as 47,XYY. Without hydrops fetalis, this may be ended with a normal outcome. Therefore, an antenatal karyotype determination should be offered to any woman whose fetus has cystic hygroma, even to those with spontaneous resolution.