Table 5. New head circumference (cm) references for 0–15 months in Dutch children with Down syndrome: values of L (skewness), M (median), and S (coefficient of variation)^*, categorized by age and sex.

	Boys			Girls
Age (weeks)	L	M	S*	L	M	S*
0	2.96	33.8	.0349	1	32.9	.0267
2	2.65	34.6	.0343	1	33.8	.0272
4	2.34	35.3	.0336	1	34.7	.0277
6	2.03	36.1	.0330	1	35.5	.0280
8	1.72	36.8	.0324	1	36.4	.0281
10	1.42	37.5	.0319	1	37.1	.0279
12	1.12	38.2	.0313	1	37.8	.0276
16	0.54	39.4	.0302	1	38.8	.0270
20	−0.01	40.4	.0292	1	39.7	.0265
24	−0.52	41.2	.0283	1	40.4	.0261
28	−0.99	42.0	.0274	1	41.0	.0259
32	−1.41	42.6	.0266	1	41.5	.0257
36	−1.80	43.1	.0258	1	42.0	.0255
40	−2.14	43.5	.0250	1	42.3	.0254
44	−2.45	43.9	.0243	1	42.7	.0252
48	−2.72	44.2	.0237	1	42.9	.0251
52	−2.97	44.4	.0231	1	43.2	.0249
56	−3.19	44.6	.0225	1	43.3	.0248
60	−3.40	44.8	.0221	1	43.5	.0247
65a	−3.64	45.0	.0216	1	43.7	.0245

^aCorresponding with 15 months.

*Individual head circumference SDS can be calculated by: SDS = {(height (cm)/M)^L−1}/L*S, L≠0 (if L = 0: SDS = ln(height (cm)/M)/S).