New Finnish reference for head circumference from birth to 7 years

Figures & data

Figure 1. The new Finnish HC for age reference (mean ± 2 SD, solid lines). Curves based on 146,790 measurements from 19,715 full-term healthy subjects born between 1986 and 2008 compared to the current Finnish HC reference based on subjects born between 1953 and 1964 (mean ± 2 SD, dashed lines). A: girls aged 0–7 years; B: boys aged 0–7 years.

Figure 2. Age- and sex-specific features of the secular change in HC in Finland. Comparison between HC reference 1986–2008 and HC reference 1953–1964. Curves indicate differences from the HC reference 1953–1964 in mean HC in cm from birth to age 7 years. Dashed line = girls; solid line = boys.

Figure 3. Age- and sex-specific features of the change in head circumference SD. Curves illustrate the ratio between the SD of the HC reference 1953–1964 and HC reference 1986–2008 (horizontal line). Dashed line = girls; solid line = boys.

Table I. Number of head circumference measurements of girls in the head circumference (HC) reference 1986–2008 population and percentage of measurements ≤ −2 SD and ≥ 2 SD when compared to the HC reference 1953–1964.

		Girls outside the ± 2 SD range of the HC reference 1953–1964
Age group	HC reference 1986–2008 Number of measurements	Percentage ≤ −2 SDS	Percentage ≥ 2 SDS
<1 mo	7696	0.6	3.0
1–2 mo	5936	0.1	6.0
2–3 mo	4326	0.1	5.5
3–4 mo	5459	0.1	3.1
4–5 mo	4558	0.2	1.9
5–6 mo	4633	0.5	1.4
6–8 mo	6078	0.6	1.2
8–10 mo	5099	0.7	1.2
10–12 mo	4154	0.9	0.9
12–18 mo	7317	0.7	0.9
18–24 mo	4669	0.7	1.2
2–3 y	4311	0.9	1.2
3–4 y	2541	0.4	1.5
4–5 y	877	0.7	3.2
5–6 y	2317	0.5	2.5
6–7 y	1498	0.1	3.5
Total	71469	0.5	2.3

HC reference 1986–2008 population includes subjects born between 1986 and 2008; HC reference 1953–1964 population includes subjects born between 1953 and 1964. Birth head circumferences are included.

Table II. Number of head circumference measurements of boys in the head circumference (HC) reference 1986–2008 and percentage of measurements ≤ −2 SD and ≥ 2 SD when compared to the HC reference 1953–1964.

		Boys outside the ± 2 SD range of the HC reference 1953–1964
Age group	HC reference 1986–2008 Number of measurements	Percentage ≤ −2 SDS	Percentage ≥2 SDS
< 1 mo	8063	1.8	2.9
1–2 mo	6200	0.1	7.0
2–3 mo	4483	0.1	7.2
3–4 mo	5868	0.1	5.5
4–5 mo	4793	0.1	3.4
5–6 mo	4795	0.1	3.6
6–8 mo	6397	0.3	2.8
8–10 mo	5395	0.3	1.9
10–12 mo	4237	0.3	0.8
12–18 mo	7785	0.5	0.6
18–24 mo	5023	0.4	0.5
2–3 y	4612	0.5	0.7
3–4 y	2693	0.7	2.2
4–5 y	961	1.0	3.1
5–6 y	2453	0.7	3.4
6–7 y	1563	0.5	4.6
Total	75321	0.5	3.1

HC reference 1986–2008 population includes subjects born between 1986 and 2008; HC reference 1953–1964 population includes subjects born between 1953 and 1964. Birth head circumferences are included.

Figure 4. HC-to-height ratio for age in boys (solid line) and girls (dashed line) (mean ± 2 SD). Subjects born between 1986 and 2008.