Limb Body Wall Complex: Report of a Discordant Case in a Monozygotic Twin Pregnancy

Limb Body Wall Complex (LBWC) is a rare, severe congenital malformation syndrome characterized by thoracoabdominal wall defects, craniofacial anomalies, and limb and spinal malformations. Its incidence ranges from 0.04 to 3.3 per 10,000 births. We present a case of LBWC diagnosed in a monochorionic diamniotic twin pregnancy at 17 weeks of gestation. The mother was 28-year-old, primigravida, and had no notable medical history. Ultrasound identified abnormal positioning of 1 embryo, suggestive of adherence to the amnion. First-trimester scans revealed increased nuchal translucency and foot malposition in fetus A, while fetus B showed a cystic hygroma along with significant abdominal wall and spinal anomalies. Selective termination of fetus B was performed at 17 weeks but was complicated by the intrauterine demise of both fetuses. Postmortem examination of fetus B confirmed classical LBWC features: abdominopelvic wall defect with evisceration adherent to the placenta, lower limb amyotrophy, severe kyphoscoliosis, and craniofacial abnormalities. The pathogenesis of LBWC remains unclear, with hypotheses including early amnion rupture, vascular disruptions, and embryonic developmental errors. Diagnosis is typically made by prenatal ultrasound in the first trimester. LBWC is generally lethal, warranting pregnancy termination. While multiple pregnancies may increase the risk, discordant presentation in monochorionic twins remains exceptionally rare.