Table 2.

Significant Sex differences in early developmental milestones

Milestone	N	M (months) male (SD)	M (months) Female (SD)	p	ηp2
Female later milestone
Smile	18,077	3.49 (4.54)	3.81 (4.450	< 0.001	0.002
Sat w/o support	18,088	6.48 (2.60)	6.89 (3.41)	< 0.001	0.005
Crawled	17,922	8.77 (3.54)	9.47 (4.57)	< 0.001	0.008
Walked	18,265	13.67 (4.33)	14.32 (5.32)	< 0.001	0.007
Male later milestone
Used words	17,899	18.87 (11.83)	18.12 (11.72)	0.008	0.001
Combining phrases	17,671	30.79 (15.96)	29.55 (15.91)	0.001	0.001
Complex sentences	15,516	40.11 (18.73)	38.62 (19.08)	0.003	0.001
Bowel trained	17,716	46.58 (15.85)	44.42 (15.77)	< 0.001	0.005
Fed self	17,800	18.10 (10.46)	17.63 (10.10)	< 0.001	0.005