What do you think of CRL and gestational weeks?

CRL and gestational age control refer to the comparison of head arm length and gestational age. If the test results are different from the control within two weeks, it is normal. Generally, head arm length is 4 mm at 6 weeks of pregnancy; 8-9 mm at 7 weeks of pregnancy; 14-15 mm at 8 weeks of pregnancy; 22 mm at 9 weeks of pregnancy; 41-42 mm at 10 weeks of pregnancy; and 66 mm at 13 weeks of pregnancy.