Table 2 Analysis results of regression analysis showing relative risk of maternal occupations for preterm and SGA birth

Maternal age group

Under 20 years

1.084 (0.999, 1.177)

0.053

0.932 (0.858, 1.013)

0.098

20–24 years

0.911 (0.877, 0.945)

< 0.001

0.991 (0.958, 1.026)

0.620

25–29 years

0.880 (0.858, 0.903)

< 0.001

0.992 (0.970, 1.015)

0.491

30–34 years

Reference

Reference

35–39 years

1.232 (1.204, 1.262)

< 0.001

1.052 (1.028, 1.077)

< 0.001

40 years or more

1.558 (1.504, 1.614)

< 0.001

1.171 (1.128, 1.216)

< 0.001

Maternal nationality

Japanese

Reference

Reference

Non-Japanese

1.096 (1.034, 1.161)

0.002

0.532 (0.492, 0.575)

< 0.001

Sex

Female

Reference

Reference

Male

1.288 (1.264, 1.312)

< 0.001

1.003 (0.986, 1.020)

0.739

Parity

Primiparous

Reference

Reference

Multiparous

1.004 (0.986, 1.024)

0.645

0.930 (0.914, 0.947)

< 0.001

Wedlock status

In wedlock

Reference

Reference

Out of wedlock

1.398 (1.318, 1.482)

< 0.001

1.240 (1.169, 1.315)

< 0.001

Household occupation

Reference

Reference

Farmer

1.062 (0.974, 1.158)

0.173

1.017 (0.935, 1.106)

0.694

Self-employed worker

1.013 (0.977, 1.050)

0.496

1.029 (0.994, 1.065)

0.110

Full-time worker 1 ^a

1.046 (1.024, 1.067)

< 0.001

1.083 (1.062, 1.105)

< 0.001

Full-time worker 2 ^b

Reference

Reference

Others

1.024 (0.989, 1.059)

0.183

1.032 (0.999, 1.066)

0.058

Unemployed

1.182 (1.107, 1.262)

< 0.001

1.246 (1.169, 1.329)

< 0.001

Maternal occupation

Unemployed persons

Reference

Reference

Administrative and managerial workers

0.975 (0.863, 1.100)

0.678

0.909 (0.802, 1.030)

0.135

Professional and engineering workers

0.979 (0.953, 1.005)

0.112

1.003 (0.978, 1.029)

0.806

Clerical workers

0.975 (0.948, 1.003)

0.076

1.026 (0.999, 1.053)

0.060

Sales workers

0.985 (0.935, 1.037)

0.564

1.062 (1.013, 1.113)

0.013

Service workers

1.031 (0.993, 1.070)

0.106

1.043 (1.007, 1.080)

0.017

Security workers

0.951 (0.798, 1.134)

0.578

0.817 (0.684, 0.977)

0.027

Agriculture, forestry, and fishery workers

0.913 (0.782, 1.066)

0.249

0.956 (0.824, 1.110)

0.557

Manufacturing process workers

1.156 (1.082, 1.234)

< 0.001

1.178 (1.107, 1.254)

< 0.001

Transport and machine operating workers

1.029 (0.823, 1.288)

0.801

0.847 (0.669, 1.072)

0.167

Construction and mining workers

0.941 (0.763, 1.160)

0.570

0.952 (0.779, 1.164)

0.631

Carrying, cleaning, packaging, and related workers

1.173 (0.965, 1.426)

0.108

0.878 (0.705, 1.094)

0.247

Workers engaged in an unclassified occupation

0.901 (0.828, 0.981)

0.017

0.987 (0.912, 1.067)

0.736