Table 1 Descriptive statistics of variables by cohort.

Outcome variables

 Birth Weight (g)

3300.91

3299.78

3404.51

 LBW

7.23

6.64

5.46

Independent variables

Maternal education

 High

24.99

33.19

33.64

 Low

75.01

66.81

66.36

 Smoking in pregnancy (SIP)

34.06

43.10

23.15

Controls

 Child is female

48.61

48.10

48.50

 Maternal height (cm)

161.01

161.02

164.34

Maternal age

  < 19

5.61

9.88

4.97

 20–29

61.01

66.87

40.49

 30–39

30.86

21.29

51.13

 40 + 

2.52

1.97

3.41

Marital status

 Married

96.43

93.13

54.96

 Non-Married

3.57

6.87

45.04

Birth order

 First born

36.51

37.67

42.66

 Second born

31.26

32.71

36.85

 Third + born

32.23

29.62

20.48

Timing of prenatal care access

 Before 12th week

20.93

31.39

43.8

 12th to 23rd week

62.50

43.05

52.36

 After 23rd week

16.04

24.94

1.41

 No visits

0.53

0.63

2.43

 N

15,500

15,552

14,619