Table 1 Comparison of characteristics of Chinese pregnant women

Age

6.78

0.03

 15–25

490

1.68(1.63–1.74)

 25–35

663

1.65(1.47– 1.84)

 35–45

56

1.57(1.51 –1.62)*

Region strata

6.62

0.08

 Large cities

287

1.63(1.56 –1.71)

 Small to medium cities

360

1.67(1.60– 1.74)

 General rural areas

291

1.65(1.57–1.73)

 Poor rural areas

271

1.59(1.49–1.68)

College or university

6.24

0.01

 No

832

1.60(1.56 –1.65)

 Yes

377

1.70(1.63–1.76)

Income

12.63

0.01

  < 10,000

199

1.58(1.52–1.63)*

 10,000–20,000

339

1.63(1.55– 1.71)

 20,000–30,000

486

1.64(1.54 –1.75)

  > =30,000

185

1.77(1.68–1.86)*

Drinkers

21.55

0.00

 No

1071

1.65(1.61–1.69)

 Yes

138

1.52(1.40–1.64)

Smoking

5.92

0.00

 Non-smoker without passive smoking

553

1.67(1.61–1.72)

 Non-smoker with passive smoking

625

1.62(1.57–1.67)

 Smokers

31

1.26(0.98–1.53)*

Gestational age

25.47

0.00

 First trimester

471

1.74(1.68–1.80)*

 Second trimester

292

1.64(1.56–1.71)

 Third trimester

446

1.52(1.46–1.58)*

Parity

7.66

0.02

 0

877

1.70(1.62–1.79)

 1

299

1.62(1.58–1.66)

 2+

33

1.36(1.14–1.59)*

Anemia

10.28

0.00

 No

916

1.67(1.63–1.71)

 Yes

293

1.52(1.45–1.60)

Vitamin A supplement

8.67

0.00

 No

1104

1.62(1.58–1.66)

 Yes

105

1.80(1.67–1.91)