Table 1 Participants’ characteristics by the Autism-Spectrum Quotient short form (Japanese version) cut-off point (N = 89,068).

	Total		< AQ-10 cut-off		≥ AQ-10 cut-off
	Total		(0–6 points)		(7–10 points)
	n = 89,068		n = 86,667		n = 2401		p-value
	n	%	n	%	n	%	< 0.001
Antenatal pain
None	14,057	15.8	13,720	15.8	337	14.0
Mild pain	55,121	61.9	53,657	61.9	1464	61.0
Moderate-to-severe pain	19,890	22.3	19,290	22.3	600	25.0
History of autism, Asperger’s syndrome, or PDD	20	0.02	9	0.01	11	0.5	< 0.001

	Mean	SD	Mean	SD	Mean	SD
Age (years)	30.8	5.0	30.8	5.0	30.2	5.2	< 0.001

	n	%	n	%	n	%
Pre-pregnancy overweight	9336	10.5	9092	10.5	244	10.2	0.60
Smoker during pregnancy	3948	4.4	3826	4.4	122	5.1	0.12
Drinker during pregnancy	41,774	46.9	40,716	47.0	1058	44.1	0.005
Low amounts of physical activity	19,940	22.4	19,330	22.3	610	25.4	< 0.001
Less than high school education	4184	4.7	4028	4.6	156	6.5	< 0.001
Divorced or widowed	763	0.9	732	0.8	31	1.3	0.02
Low income	29,762	33.4	28,875	33.3	887	36.9	< 0.001
Full-time homemaker	39,424	44.3	38,281	44.2	1,143	47.6	< 0.001
Multiple pregnancy	867	1.0	844	1.0	23	1.0	0.94
History of delivery	43,656	49.0	42,608	49.2	1048	43.6	< 0.001
History of anxiety disorder	2531	2.8	2397	2.8	134	5.6	< 0.001
History of depression	2703	3.0	2557	3.0	146	6.1	< 0.001
History of schizophrenia	151	0.2	139	0.2	12	0.5	< 0.001
History of other psychological disorders	871	1.0	827	1.0	44	1.8	< 0.001
Confusion/upset when made aware of the pregnancy	6592	7.4	6332	7.3	260	10.8	< 0.001
Sleeping quite lightly	6378	7.2	6147	7.1	231	9.6	< 0.001
Psychological distress during pregnancy	2914	3.3	2699	3.1	215	9.0	< 0.001

AQ-10 Autism-Spectrum Quotient short form, PDD pervasive developmental disorders, SD standard deviation.
Criteria for developmental disorders in the questionnaire were based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). Body mass index ≥ 25 kg/m² was defined as overweight. The first quintile of amounts of physical activity was defined as low amounts of physical activity. Equivalized income < 1.22 million Japanese yen was defined as low income. A Kessler Psychological Distress Scale (K6) score ≥ 13 was interpreted as indicating the presence of psychological distress during pregnancy. T-tests were used to compare groups on continuous variables. Chi-square analyses were conducted for categorical data.

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