OB Dating Atlas - Week 10 - Crown Rump Length (CRL)
Caption
A 24-year-old G0 with an unknown LMP presents for a missed period and confirmation of pregnancy. She had a positive UPT 5 days ago. On abdominal ultrasound, an embryo is visualized. The crown-rump length measures 3.84 cm consistent with a 10w5d IUP. General Rules: Most accurate single measurement once the embryo is present (6w0d-13w6d) [1] Mean of 3 linear measurements from the outer margin of the cranium/cephalic pole to caudal rump in the true midsagittal plane. Gestational Age (weeks) = CRL (cm) + 6.5 This equation can be used when using a portable or handheld device that does not auto calculate the gestational age. Accuracy3: ± 5 - 7 days