FL by gestational age weeks -1.64SD -1.5SD -1.28SD mean +1.28SD +1.5SD +1.64SD 16 17.1 17.4 18.0 21.4 24.8 25.4 25.8 17 19.6 19.9 20.5 24.0 27.4 28.0 28.4 18 22.1 22.5 23.1 26.5 30.0 30.6 31.0 19 24.6 25.0 25.6 29.1 32.6 33.2 33.6 20 27.1 27.4 28.1 31.6 35.2 35.8 36.2 21 29.5 29.9 30.5 34.1 37.8 38.4 38.8 22 31.9 32.3 33.0 36.6 40.3 40.9 41.3 23 34.3 34.7 35.4 39.1 42.8 43.4 43.8 24 36.7 37.1 37.7 41.5 45.2 45.9 46.3 25 39.0 39.4 40.1 43.9 47.7 48.3 48.7 26 41.3 41.7 42.4 46.2 50.0 50.7 51.1 27 43.5 43.9 44.6 48.4 52.3 53.0 53.4 28 45.6 46.1 46.7 50.6 54.6 55.2 55.7 29 47.7 48.1 48.8 52.8 56.7 57.4 57.9 30 49.7 50.1 50.8 54.8 58.8 59.5 60.0 31 51.6 52.1 52.8 56.8 60.9 61.6 62.0 32 53.5 53.9 54.6 58.7 62.8 63.5 64.0 33 55.2 55.7 56.4 60.5 64.7 65.4 65.8 34 56.9 57.3 58.0 62.2 66.4 67.1 67.6 35 58.4 58.9 59.6 63.8 68.1 68.8 69.2 36 59.9 60.3 61.1 65.3 69.6 70.3 70.8 37 61.2 61.7 62.4 66.7 71.0 71.8 72.2 38 62.4 62.9 63.6 68.0 72.3 73.1 73.6 39 63.5 64.0 64.7 69.1 73.5 74.3 74.7 40 64.4 64.9 65.7 70.1 74.6 75.3 75.8 41 65.3 65.7 66.5 71.0 75.5 76.2 76.7 42 65.9 66.4 67.2 71.7 76.2 77.0 77.5