Early diagnosis of fetal defects

At 8–10 weeks all fetuses demonstrate herniation of the midgut that is visualized as a hyperechogenic mass in the base of the umbilical cord. Retraction into the abdomen occurs at 10–12 weeks and it is completed by 11⁺⁵ weeks.

• At 11-13 weeks the prevalence of exomphalos is about 1 in 1000, which is four times higher than in live births. The condition is usually sporadic.
• The incidence of chromosomal defects, mainly trisomy 18, is about 60%, compared to about 30% at mid-gestation and 15% in neonates, because trisomy 18 is associated with a high rate of intrauterine death.
• The risk for chromosomal defects is higher if the exomphalos sac contains only bowel rather than liver.
• Increased NT is observed in about 85% of chromosomally abnormal and 40% of chromosomally normal fetuses with exomphalos.