Fetus Crown Rump Length (CRL) Measurements Ultrasound

    The fetal crown rump length (CRL) is defined as the longest length excluding the limbs and yolk sac. It is the measurement between the top of the head to the area above where the legs begin and is done by ultrasound usually up to the 14th week of the pregnancy.

    CRL



    The original definition of a crown rump length (CRL) was by Mall in 1907. The CRL is the sitting height, mid brain to the lowest point of breech.

    Days                   (LMP) Days (Fertilization) (weeks/days) (mm)
    37 23 5.2 1
    38 24 5.3 2
    39 25 5.4 3
    40 26 5.5 3
    41 27 5.6 4
    42 28 6 4
    43 29 6.1 5
    44 30 6.2 6
    45 31 6.3 7
    46 32 6.4 8
    47 33 6.5 9
    48 34 6.6 10
    49 35 7 11
    50 36 7.1 11
    51 37 7.2 12
    52 38 7.3 12
    53 39 7.4 13
    54 40 7.5 14
    55 41 7.6 15
    56 42 8 17
    57 43 8.1 18
    58 44 8.2 19
    59 45 8.3 20
    60 46 8.4 21
    61 47 8.5 22
    62 48 8.6 22
    63 49 9 23
    64 50 9.1 24
    65 51 9.2 26
    66 52 9.3 27
    67 53 9.4 28
    68 54 9.5 29
    69 55 9.6 31
    70 56 10 34
    71 57 10.1 36
    72 58 10.2 37
    73 59 10.3 38
    74 60 10.4 39
    75 61 10.5 39
    76 62 10.6 40
    77 63 11 44
    78 64 11.1 45
    79 65 11.2 47
    80 66 11.3 48
    81 67 11.4 52
    82 68 11.5 55
    83 69 11.6 56
    84 70 12 57
    85 71 12.1 58
    86 72 12.2 60
    87 73 12.3 61
    88 74 12.4 63
    89 75 12.5 64
    90 76 12.6 65
    91 77 13 68
    92 78 13.1 70
    93 79 13.2 72
    94 80 13.3 74
    95 81 13.4 76
    96 82 13.5 77
    97 83 13.6 80
    98 84 14 81
    99 85 14.1 84
    100 86 14.2 85
    101 87 14.3 86
    102 88 14.4 87