Table 2.

Number of participants and their age distributions at the four nominal testing ages (F: female; M: male).

		6-mo	12-mo	18-mo	24-mo
Low-risk	Number	2 F/3 M	9 F/10 M	9 F/10 M	8 F/8 M
	Actual age	6.0 ± 0.7 mo	11.3 ± 1.3 mo	17.4 ± 0.5 mo	23.7 ± 0.5
High-risk	Number	5 F/6 M	9 F/13 M	8 F/12 M	6 F/8 M mo
	Actual age	6.3 ± 0.8 mo	12.2 ± 1.1 mo	17.6 ± 0.6 mo	23.4 ± 0.5 mo