Table 1 Main demographic characteristics of the study population

Maternal age, year^b

28.3 ± 5.6

29.6 ± 5.2

0.96

0.93–0.99

0.004

Caucasian, n (%)

177 (84)

341 (83)

1.12

0.71–1.75

0.63

Smoking, n (%)

62 (30)

69 (17)

2.08

1.41–3.09

<0.001

Alcohol, n (%)

12 (6)

7 (2)

3.51

1.36–9.04

0.009

Street drugs, n (%)

15 (7)

8 (2)

3.89

1.12–9.32

0.002

Educational status

0.008^c

High school diploma or less, n (% of known status)

34 (45)

37 (25)

Undergraduate degree, n (% of known status)

35 (46)

99 (66)

0.39^d

0.21–0.70

0.002

Graduate degree, n (% of known status)

7 (9)

14 (9)

0.54^d

0.19–1.51

0.24

Marital status

0.43^c

Pre-pregnant BMI^b

26 ± 6.7

26 ± 6.2

1.00

0.97–1.03

0.93

Parity

0.78 ± 1

0.68 ± 0.89

1.12

0.93–1.33

0.21

Previous miscarriage, n (%)

68 (32)

96 (23)

1.58

1.09–2.28

0.015

ART, n (%)

6 (3%)

13 (3%)

0.79

0.30–2.09

0.63

Gestational age, wks^b

33.7 ± 2.5

39.7 ± 1.0

<0.001

Birth weight, g^b

2269 ± 584

3531 ± 461

<0.001