Table 1.

Sample mean values for main control variables in LSAC B cohort.

	Mode of birth				p-value of diff.a
	Cesarean	s.e.	Vaginal	s.e.
	(n=1,080)		(n=2,586)
Dependent variables b
Survey-based measures
School preparedness (WAI), 4–5	65.3	5.9	65.8	6.0	[0.112]
Vocabulary (PPVT), 4–5	65.4	8.8	65.3	8.4	[0.784]
Vocabulary (PPVT), 6–7	74.8	5.1	74.5	5.0	[0.134]
Vocabulary (PPVT), 8–9	79.5	4.6	79.3	4.9	[0.143]
Problem solving (MR), 6–7	10.8	3.1	10.8	3.0	[0.601]
Problem solving (MR), 8–9	10.5	2.9	10.6	3.0	[0.673]
Grade 3 NAPLAN
Numeracy	409.2	72.9	412.0	74.8	[0.359]
Reading	436.3	90.5	439.4	90.0	[0.395]
Writing	423.2	62.0	425.7	59.5	[0.313]
Spelling	419.4	78.4	420.9	77.9	[0.641]
Grammar	438.8	96.9	441.6	91.9	[0.481]
Controls c
Family characteristics (socio-economic status (SES)) in year of birth
Maternal age at birth	31.752	4.810	30.438	5.159	[0.000]
Maternal age at birth squared	1031	307	953	313	[0.000]
Three or more older siblings	0.041	0.198	0.073	0.261	[0.000]
Female child	0.457	0.498	0.500	0.500	[0.019]
Either parent was born in a disadvantaged countryd	0.046	0.210	0.071	0.257	[0.002]
Mother is single	0.051	0.220	0.068	0.252	[0.040]
Mother is not legally married to partner	0.804	0.397	0.769	0.421	[0.018]
Mother was employed	0.532	0.499	0.532	0.499	[0.969]
Mother’s highest qualification
High school diploma or belowe	0.256	0.436	0.292	0.455	[0.022]
Vocational education qualificationf	0.261	0.439	0.263	0.441	[0.889]
College (bachelor) degree or above	0.483	0.500	0.444	0.497	[0.031]
Private health insurance	0.591	0.492	0.488	0.500	[0.000]
Perinatal risk factors (PN)
Low birthweight (<2.5 kg)	0.066	0.248	0.034	0.181	[0.000]
IVF treatment used	0.085	0.279	0.052	0.222	[0.000]
Multiple births	0.064	0.245	0.017	0.128	[0.000]
Head circumference of child (Z-score)g	−0.262	1.119	−0.326	0.871	[0.090]
Length of baby when born (Z-score)g	0.054	1.382	0.377	0.988	[0.000]
Blood pressure medication during pregnancy	0.030	0.170	0.016	0.126	[0.020]
Diabetes medication during pregnancy	0.021	0.144	0.006	0.076	[0.001]
Antibiotic medication during pregnancy	0.108	0.311	0.098	0.297	[0.345]
Weeks of gestation	38.563	2.084	39.462	1.695	[0.000]
State of residence
New South Wales	0.279	0.449	0.320	0.466	[0.013]
Victoria and Australian Capital Territory	0.281	0.450	0.272	0.445	[0.553]
Western Australia	0.117	0.321	0.097	0.297	[0.091]
Queensland	0.212	0.409	0.200	0.400	[0.411]
South Australia	0.076	0.265	0.071	0.256	[0.588]
Northern Territory	0.009	0.096	0.018	0.132	[0.029]
Tasmania	0.026	0.159	0.022	0.148	[0.536]
Outside metropolitan areas	0.348	0.477	0.375	0.484	[0.121]

^aThe p-values are associated with a t-test for differences in mean values between cesarean and vaginally born children. ^bThe descriptive results above are age-normalised, but unstandardized to give the reader a fuller picture of the data. In the regression analysis, all cognitive performance measures are age-normalised and standardised with respect to the weighted sample mean and standard deviation. ^cAll control variables are taken from wave 1 of the data (2004) when children are 0–1 year of age. ^dDisadvantaged countries are those identified by the Australian Bureau of Statistics Standard Australian Classification of Counties (2011), ABS cat. no. 1269.0. ^eHigh school diploma includes vocational equivalent — International Standard Classification of Education (ISCED) 1997 level 3 C. ^fVocational education qualification is ISCED 1997 level 4B and 5 A. ^gZ-scores are based on Centre for Disease Control and Prevention (CDC) growth charts and are age and gender-adjusted.