Membranous fetal vessels mimicking amniotic band syndrome: furcate cord insertion in a bilobed placenta

Objective: Membranous fetal vessels may mimic amniotic band syndrome, creating diagnostic uncertainty. We describe a case in which color Doppler redirected the diagnosis from a presumed amniotic band toward furcate cord insertion in a bilobed placenta. Study Design: Single case report of a 33-year-old gravida 3 para 2 evaluated with serial transabdominal and transvaginal ultrasound with color Doppler, correlated with gross placental examination after delivery. Results: Ultrasound at 19+6 weeks demonstrated a membranous sheet spanning the lower uterine segment without direct fetal involvement, initially suggesting amniotic band syndrome. Color Doppler revealed fetal vessels within the membrane, raising concern for abnormal cord insertion and vasa previa. Transvaginal color Doppler localized these vessels more than 3 cm from the internal cervical os, arguing against type I vasa previa. Surveillance and antenatal testing remained reassuring, and a cesarean at 37+3 weeks yielded a healthy neonate. Gross examination confirmed a bilobed placenta with furcate separation of umbilical vessels inserting velamentously into each lobe and converging into a three-vessel cord. Conclusion: Membranous fetal vessels from furcate cord insertion may mimic both amniotic band syndrome and vasa previa. Color Doppler interrogation of any intrauterine band-like structure is essential to establish the correct diagnosis and guide management.