Sonographic Detection of Chromosomal Abnormalities

TABLE G-1

Distribution of Nuchal Translucency Measurements by Crown-Rump Length

Crown-Rump Length (mm)	Gestational Age (wk)	N	Mean (mm)	Median (mm)	Standard Deviation (mm)	PERCENTILE CUTPOINT (mm)			PERCENTILE CUTPOINT (MoM)			Percentile Equivalent at 3.5 mm
Crown-Rump Length (mm)	Gestational Age (wk)	N	Mean (mm)	Median (mm)	Standard Deviation (mm)	90th	95th	99th	90th	95th	99th	Percentile Equivalent at 3.5 mm
45.0	11.3	404	1.17	1.1	0.31	1.5	1.7	2.0	1.31	1.42	1.82	99.8
46.0	11.4	620	1.22	1.2	0.38	1.6	1.8	2.9	1.37	1.58	2.45	99.6
47.0	11.5	667	1.21	1.2	0.33	1.6	1.8	2.2	1.30	1.44	2.02	99.8
48.0	11.6	796	1.26	1.2	0.39	1.7	1.9	2.9	1.35	1.55	2.32	99.6
49.0	11.7	853	1.25	1.2	0.33	1.6	1.8	2.5	1.28	1.45	1.90	99.8
50.0	11.7	1048	1.29	1.2	0.36	1.7	1.8	2.6	1.34	1.49	2.08	99.7
51.0	11.8	1256	1.31	1.2	0.38	1.7	1.9	2.8	1.34	1.53	2.17	99.8
52.0	11.9	1401	1.31	1.3	0.30	1.7	1.8	2.3	1.29	1.40	1.71	99.9
53.0	12.0	1783	1.35	1.3	0.39	1.7	1.9	2.6	1.32	1.44	1.98	99.7
54.0	12.0	1919	1.37	1.3	0.34	1.8	2.0	2.4	1.33	1.47	1.83	99.8
55.0	12.1	2089	1.41	1.4	0.42	1.8	2.0	2.6	1.32	1.46	2.02	99.6
56.0	12.2	2247	1.42	1.4	0.36	1.8	2.0	2.6	1.33	1.45	1.89	99.7
57.0	12.3	2439	1.44	1.4	0.35	1.8	2.0	2.5	1.33	1.46	1.85	99.9
58.0	12.3	2695	1.48	1.4	0.39	1.9	2.1	2.6	1.35	1.48	1.92	99.6
59.0	12.4	2831	1.51	1.5	0.42	1.9	2.1	2.8	1.35	1.49	1.93	99.6
60.0	12.5	3011	1.54	1.5	0.39	2.0	2.2	2.7	1.38	1.50	1.98	99.7
61.0	12.6	3050	1.55	1.5	0.37	2.0	2.2	2.6	1.35	1.50	1.79	99.8
62.0	12.6	3185	1.57	1.5	0.37	2.0	2.2	2.8	1.36	1.48	1.91	99.8
63.0	12.7	3156	1.60	1.5	0.38	2.1	2.3	2.7	1.35	1.48	1.85	99.8
64.0	12.8	3217	1.62	1.6	0.41	2.1	2.3	2.8	1.38	1.51	1.81	99.8
65.0	12.8	3125	1.64	1.6	0.39	2.1	2.3	2.8	1.35	1.47	1.83	99.7
66.0	12.9	3171	1.67	1.6	0.42	2.2	2.4	2.9	1.37	1.50	1.91	99.6
67.0	13.0	3083	1.69	1.6	0.42	2.2	2.4	2.8	1.37	1.51	1.81	99.7
68.0	13.1	2872	1.70	1.7	0.40	2.2	2.4	2.8	1.35	1.50	1.76	99.9
69.0	13.1	2779	1.72	1.7	0.41	2.2	2.4	2.9	1.35	1.46	1.80	99.8
70.0	13.2	2662	1.74	1.7	0.40	2.2	2.4	2.9	1.35	1.46	1.78	99.8
71.0	13.3	2483	1.79	1.7	0.41	2.3	2.5	3.0	1.37	1.48	1.77	99.7
72.0	13.4	2337	1.78	1.7	0.43	2.3	2.5	3.0	1.34	1.48	1.79	99.7
73.0	13.4	2150	1.79	1.8	0.43	2.3	2.5	2.9	1.34	1.45	1.74	99.7
74.0	13.5	2015	1.82	1.8	0.44	2.3	2.5	3.0	1.34	1.45	1.83	99.7
75.0	13.6	1920	1.80	1.8	0.43	2.3	2.5	3.1	1.31	1.49	1.75	99.7
76.0	13.7	1799	1.83	1.8	0.44	2.4	2.6	3.1	1.30	1.42	1.75	99.6
77.0	13.8	1542	1.85	1.8	0.45	2.4	2.6	3.3	1.30	1.43	1.75	99.4
78.0	13.8	1477	1.81	1.8	0.44	2.4	2.5	3.1	1.29	1.42	1.73	99.5
79.0	13.9	1215	1.85	1.8	0.47	2.4	2.5	3.0	1.27	1.38	1.65	99.7
80.0	14.0	778	1.84	1.8	0.43	2.4	2.7	3.1	1.27	1.39	1.69	99.8
81.0	14.1	625	1.86	1.8	0.45	2.4	2.7	3.2	1.24	1.39	1.67	99.6
82.0	14.2	592	1.86	1.8	0.45	2.4	2.6	3.3	1.23	1.33	1.66	99.4
83.0	14.2	611	1.85	1.8	0.44	2.4	2.6	2.8	1.18	1.27	1.47	99.8
84.0	14.2	383	1.86	1.8	0.45	2.5	2.6	3.1	1.23	1.35	1.84	99.7