A 29-year-old primigravida was referred at 30 weeks’ gestation for an ultrasonographic examination to evaluate fetal growth after a positive screening for gestational diabetes. Her previous medical history was non-contributory and a first trimester scan, performed because of uncertain dates, revealed a biometry consistent with a 14-week fetus and no obvious fetal anomalies.

A local scan before a referral at 28 weeks revealed suboptimal fetal growth but normal amniotic fluid volume. At referral, the fetal growth was below the 10^th centile, normal Doppler and normal amniotic fluid volume. In addition, lymphedema in all four extremities in association with a single umbilical artery was noted.

There was no nuchal thickening, and the four chamber view was reported as normal. A presumptive diagnosis of Hereditary lymphedema I . Accordingly, prenatal karyotyping was not recommended. Follow-up scans were done weekly and an elective cesarean section was performed at 37 weeks' gestation delivering a 2900 g female fetus with Apgar scores of 9 and 9 at 1 and 5 minutes, respectively. Lymphedema of all extremities was evident. Lymphocyrte culture confirmed a 45,X karyotype. Further neonatal evaluation revealed normal chest X-ray, and normal head and abdominal scans. Echocardiography showed a small ventricular septal defect. The infant was discharged in good condition.

However, she developed progressive right pleural effusion requiring puncture and aspiration at 1 month of age. Analysis of the aspirated fluid confirmed a chylothorax. She is currently asymptomatic and in good condition.

Conclusion: Monosomy X