- Subject is a pregnant woman carrying a live singleton fetus at the 36+0-36+6 weeks scan, with no major abnormalities appearing during prenatal imaging with no major abnormalities appearing during prenatal imaging potentially affecting the correct use of the Hadlock formula for US-EFW. Conditions such as congenital diaphragmatic hernia with decreased abdominal circumference could be underestimated by the Hadlock USEFW. Another example is a massive sacro-coccygial teratomas.