Table 4. Baseline profiles of children in the JECS Main Study and Sub-Cohort Study.

Variables	JECS Sub-Cohort Study			JECS Main Studya
	Number of valid response	n		Number of valid response	n
Number of live births	5,017			100,148
Singleton births, %		4,946	98.6		98,259	98.1
Gestational age at birth, weeks	5,017			100,148
Total, mean (SD)		5,017	39.3 (1.5)		100,148	39.2 (1.7)
Preterm births (<37), %		226	4.5		5,599	5.6
Term births (37–41), %		4,783	95.3		94,322	94.2
Postterm births (≥42), %		8	0.2		227	0.2
Sex	5,017			100,137
Male, %		2,554	50.9		51,316	51.2
Female, %		2,463	49.1		48,821	48.8
Type of delivery	5,009			99,884
Vaginal, %		4,068	81.2		79,783	79.9
Caesarean, %		941	18.8		20,101	20.1
Birth weight, g	5,017			100,071
Total, mean (SD)		5,017	3,040 (414)		100,071	3,008 (434)
Singleton births	4,946			98,182
Total, mean (SD)		4,946	3,050 (405)		98,182	3,023 (420)
Male, mean (SD)		2,523	3,095 (413)		50,312	3,065 (426)
Female, mean (SD)		2,423	3,003 (391)		47,863	2,979 (408)
Low birth weight (<2,500), %		358	7.2		7,981	8.1
Birth height, cm	5,000			99,785
Total, mean (SD)		5,000	49.0 (2.2)		99,785	48.8 (2.4)
Singleton births	4,929			97,912
Total, mean (SD)		4,929	49.0 (2.1)		97,912	48.9 (2.3)
Male, mean (SD)		2,512	49.3 (2.2)		50,166	49.2 (2.3)
Female, mean (SD)		2,417	48.8 (2.0)		47,740	48.6 (2.3)
Birth head circumference, cm	4,990			99,538
Total, mean (SD)		4,990	33.2 (1.5)		99,538	33.2 (1.5)
Singleton births	4,921			97,692
Total, mean (SD)		4,921	33.2 (1.5)		97,692	33.2 (1.5)
Male, mean (SD)		2,510	33.5 (1.5)		50,054	33.4 (1.5)
Female, mean (SD)		2,411	33.0 (1.4)		47,633	33.0 (1.5)
Birth chest circumference, cm	4,988			99,489
Total, mean (SD)		4,988	31.8 (1.8)		99,489	31.7 (1.9)
Singleton births	4,919			97,653
Total, mean (SD)		4,919	31.9 (1.7)		97,653	31.8 (1.8)
Male, mean (SD)		2,510	32.0 (1.8)		50,034	31.9 (1.9)
Female, mean (SD)		2,409	31.7 (1.7)		47,614	31.6 (1.8)

SD, standard deviation.

^aMichikawa et al, J Epidemiol 2018;28(2):99–104 (reference No. 2).