Table 1.

Characteristics of SWS parents and their children by whether or not the children had grip strength measurements at four-years of age

Characteristic	Without grip strength		With grip strength
	n		n		P-value
Mother
Mother’s age at child’s birth (y) (mean(S.D.))	1194	30.3 (3.8)	968	30.8 (3.7)	0.002
Mother’s height (cm) (mean(S.D.))	1188	162.9 (6.4)	962	163.7 (6.5)	0.005
Mother’s pre-pregnant weight (kg) (median(IQR))	1184	64.4 (57.1 to 73.6)	959	65.2 (59.3 to 73.2)	0.06
Mother’s pre-pregnant BMI (kg/m2) (median(IQR))	1183	24.2 (21.8 to 27.6)	958	24.3 (22.2 to 27.3)	0.4
Mother’s educational attainment (n(%))
No degree		957 (80.4)		721 (74.7)	0.02
Degree level and above		234 (19.6)		244 (25.3)
Father
Father’s age at child’s birth (y) (mean(S.D.))	932	32.8 (5.5)	759	33.3 (5.0)	0.04
Father’s height (cm) (mean(S.D.))	736	177.8 (7.0)	463	178.0 (6.8)	0.7
Father’s social class (n(%))
Manual		476 (56.3)		505 (56.9)	0.8
Non-manual		370 (43.7)		383 (43.1)
Child
Sex (n(%))
Male		630 (52.9)		501 (51.8)	0.6
Female		562 (47.1)		467 (48.2)
Birth weight (kg) (mean(S.D.))	1175	3.42 (0.57)	960	3.48 (0.52)	0.02
Birth weight, CGF z-score (mean(S.D.))	1175	−0.02 (0.97)	960	0.06 (0.91)	0.04
Birth weight below tenth centile for gestational age (n(%))	1175	106 (9.0)	960	60 (6.3)	0.02
Gestational age (weeks) (mean(S.D.))	1194	39.7 (2.0)	968	39.8 (1.8)	0.07
Height at 4 year visit (cm) (mean(S.D.))			967	104.0 (4.0)
Height at 4 y visit, CGF z-score (mean(S.D.))			967	0.28 (0.97)
Weight at 4 year visit (kg) (median(IQR))			964	17.1 (15.8 to 18.6)
Weight at 4 y visit, CGF z-score (mean(S.D.))			964	0.25 (1.02)
Grip strength at 4 year visit (kg) (mean(S.D.))			968	8.3 (1.7)

IQR = interquartile range.