Vaginal delivery (n=60,883) Cesarean delivery (n=13,756) p value
n % n %
Maternal age at pregnancy (years) <0.001
<20 405 0.7 50 0.4
20-29 24,436 40.1 3,908 28.4
30-39 34,254 56.3 8,889 64.6
>=40 1,788 2.9 909 6.6
Parity 0.002
0 18,167 29.8 3,920 28.5
1 21,140 34.7 4,774 34.7
>=2 21,576 35.4 5,062 36.8
Sex (male) 31,124 51.1 7,051 51.3 0.772
Gestational age (weeks) <0.001
<37 1,834 3.0 1,374 10.0
37 3,738 6.1 3,281 23.9
38 11,012 18.1 5,742 41.7
39-41 44,299 72.8 3,359 24.4
SGA 1,882 3.1 672 4.9 <0.001
Maternal allergies 31,399 51.6 7,115 51.7 0.75
Maternal smoking during pregnancy 2,227 3.7 566 4.1 0.011
passive smoking during pregnancy 21,644 35.6 5,003 36.4 0.07
Maternal education periods (year) 0.008
<10 2,278 3.7 512 3.7
10-12 18,943 31.1 4,449 32.3
13-16 38,717 63.6 8,554 62.2
>=17 945 1.6 241 1.8
Annual family income (JPY) 0.003
<2,000,000 3,059 5.0 742 5.4
2,000,000-5,999,999 41,277 67.8 9,113 66.2
6,000,000-9,999,999 13,954 22.9 3,258 23.7
>=10,000,000 2,593 4.3 643 4.7
Marriage 58,786 96.6 13,307 96.7 0.293
Breastfeeding at 6 mo 46,313 76.1 9,773 71.0 <0.001
Pet owner 14,341 23.6 3,380 24.6 0.011
Passive smoking exposure of infants at 1 mo 30,730 50.5 6,897 50.1 0.477
Allergy disease
Asthma 1,514 2.5 371 2.7 0.156
Atopic dermatitis 2,666 4.4 581 4.2 0.42
Wheezing 11,871 19.5 2,777 20.2 0.066
Eczema 11,562 19.0 2,486 18.1 0.013
SGA: small gestational age; JPY: Japanese yen. SGA: small gestational age; JPY: Japanese yen. SGA: small gestational age; JPY: Japanese yen. SGA: small gestational age; JPY: Japanese yen. SGA: small gestational age; JPY: Japanese yen. SGA: small gestational age; JPY: Japanese yen.
The p value was determined using the chi-square test. The p value was determined using the chi-square test. The p value was determined using the chi-square test. The p value was determined using the chi-square test. The p value was determined using the chi-square test. The p value was determined using the chi-square test.