Variable

Maternal age (mean ± SD)

Mann-Whitney test

P value

Taking folic acid

Yes

38.18 ± 2.62

3.03

0.041

No

36.33 ± 1.11

Taking vitamin supplements

Yes

38.18 ± 2.62

0.89

0.372

No

37.13 ± 2.03

Smoking status

Smoker

35.5 ± 0.7

1.5

0.152

Nonsmoker

38.15 ± 2.68

Medications during current pregnancy

Yes

37.92 ± 2.59

5

0.616

No

38.18 ± 2.78

Postdate pregnancy (>40 weeks)

Yes

37.61 ± 2.34

2

0.556

No

38.24 ± 2.74

Missing data

38.08 ± 2.73