Table 1 Comparison of the general status (χ ± S)

Age (year)

28.59 ± 4.36

28.27 ± 4.69

28.74 ± 4.38

0.312

0.732

Height (cm)

163.22 ± 13.55

162.23 ± 13.85

158.97 ± 8.82

1.882

0.154

Weight (kg)

67.69 ± 9.79

66.59 ± 10.16

68.54 ± 8.67

0.997

0.370

Gestation ( weeks )

39.47 ± 1.04

39.46 ± 0.97

39.41 ± 1.08

0.106

0.899

Gravidity

1.80 ± 0.93

1.82 ± 1.10

1.73 ± 1.04

0.203

0.816

Parity

1.43 ± 0.58

1.42 ± 0.67

1.33 ± 0.53

0.797

0.451

Pregnancy education (Y/N)

133/59

92/35

43/20

1.571

0.456

Maternal education

1.035

0.904

 Below high school

40

27

12

 Junior college and undergraduate

129

84

53

 Postgraduate

23

16

8

Family income per year

4.485

0.344

 > 20,000yuan (RMB)

39

24

16

 10,000–20,000 yuan (EMB

91

73

33

 < 10,000 yuan (RMB)

62

30

24