First-trimester umbilical cord cysts.

Cystic masses of the umbilical cord have been detected in the 2nd and 3rd trimesters of pregnancy in association with fetal abdominal wall defects and chromosomal anomalies. With high-resolution endovaginal ultrasound (US), umbilical cord cysts can be visualized during the 1st trimester. Their origin and significance must be considered for proper obstetric management. The authors report eight cases in which cystic masses of the umbilical cord were detected during US examinations performed at 8-9 weeks menstrual age. In the five cases followed to term, both the infant and the umbilical cord were found to be normal at physical examination. Sonographically, all cysts appeared to be eccentric in relation to the umbilical cord, and, although all were closer to the fetus, the cysts were clearly extraembryonic. Cyst size was 2.0-7.5 mm (mean, 5.2 mm). Seven cysts resolved by 12 weeks menstrual age. The incidence of cysts in patients who underwent US at the authors' institution between 8 and 12 weeks menstrual age was 0.4%; the true frequency is unknown without routine 1st-trimester scanning of all patients.