Table 1 Demographic and risk factors for sPTB among all participants and according to specific progesterone treatment

Demographic factors and reproductive history before the index pregnancy

 Age

30.8 ± 6.0

31.0 ± 6.0

0.17

31.0 ± 6.1

0.25

30.7 ± 5.2

0.5

30.5 ± 5.9

 Gravida

4 (3–5)

4 (3–5)

0.012

4 (3–5)

< .001

4 (3–5)

0.615

4 (3–6)

 Parity

2 (1–3)

2 (1–3)

< .001

2 (1–2)

< .001

2 (1–3)

0.0441

2 (1–3)

^dRace/Ethnicity

^e0.89

^e0.73

^e0.49

 Non-Hispanic White

29 (4.6)

16 (4.6)

11 (3.7)

4 (9.5)

14 (4.6)

 Non-Hispanic Black

75 (11.8)

41 (11.8)

34 (11.4)

6 (14.3)

34 (11.8)

 Hispanic/Latina

460 (72.2)

258 (74.1)

223 (75.0)

28 (66.7)

201 (69.8)

 Asian/Pacific Islander

13 (2.0)

8 (2.3)

8 (2.7)

0 (0)

5 (1.7)

 Other

50 (7.8)

23 (6.6)

19 (6.4)

3 (7.1)

27 (9.4)

 BMI

31.9 ± 7.1

32.1 ± 7.6

0.5

32.3 ± 7.7

0.36

30.1 ± 6.8

0.76

31.5 ± 6.4

 Term delivery number

1 (0–2)

1 (0–1)

< .001

1 (0–1)

< .001

1 (0–2)

0.367

1 (0–2)

 Preterm delivery number

1 (1–2)

1 (1–2)

0.829

1 (1–2)

0.798

1 (1–2)

0.808

1 (1–2)

Demonstrated and Proposed Risk Factors for sPTB

 Total Maternal weight gain

10.7 ± 6.4

10.4 ± 6.3

0.67

10.7 ± 6.6

0.65

9.1 ± 4.5

0.82

11.2 ± 6.7

 Gestational age of earliest sPTB

32 (27–35)

32 (25–35)

< .001

32 (26–34)

< .001

32 (27–35)

0.044

34 (30–36)

 Number of spontaneous preterm births 1

498 (78.2)

275 (79.0)

234 (78.8)

35 (83.3)

222 (77.1)

 2

102 (16.0)

53 (15.2)

44 (14.8)

6 (14.3)

49 (17.0)

 3 or more

37 (5.8)

20 (5.7)

0.89

19 (6.4)

0.89

1 (2.4)

0.93

17 (5.9)

 Chronic Hypertension

53 (8.3)

29 (8.3)

0.47

26 (8.6)

0.63

3 (7.1)

0.63

24 (8.3)

 Pregestational Diabetes

50 (7.8)

34 (9.8)

0.026

31 (10.4)

0.034

2 (4.8)

0.2

16 (5.6)

 Short Cervix

74 (11.6)

59 (17.0)

< .001

45 (15.2)

< .001

10 (23.8)

0.001

15 (5.2)

 Tobacco Use

42 (6.6)

15 (4.3)

0.055

14 (4.7)

0.054

1 (2.4)

0.89

27 (9.4)

 Alcohol Use

7 (1.1)

4 (1.1)

1

3 (1.0)

1

0 (0)

1

3 (1.0)

 Illicit Substance Use

67 (10.5)

32 (9.2)

0.094

29 (9.8)

0.17

3 (7.1)

0.4

35 (12.2)

 Short inter-pregnancy interval

76 (11.9)

43 (12.4)

0.92

37 (12.5)

0.94

4 (9.5)

0.79

33 (11.5)

 UTI

155 (24.3)

103 (27.0)

0.25

75 (25.3)

0.45

14 (33.3)

0.17

62 (21.5)

 STI

60 (9.4)

32 (9.2)

0.69

26 (8.8)

0.61

6 (14.3)

0.71

28 (9.7)

 BV

91 (14.3)

63 (18.1)

0.002

53 (17.8)

0.007

8 (19.0)

0.016

28 (9.7)

 Antepartum vaginal bleeding

43 (6.8)

26 (7.5)

0.69

23 (7.7)

0.7

2 (4.8)

1

17 (5.9)

 Prior LEEP or CKC

7 (1.1)

2 (0.6)

0.43

2 (0.7)

0.36

1 (2.4)

1

5 (1.7)

 History of uterine instrumentation

93 (14.6)

58 (16.7)

0.17

48 (16.2)

0.24

8 (19.0)

0.28

35 (12.2)

 Periodontal Disease

5 (0.8)

2 (0.6)

1

1 (0.3)

0.56

1 (2.4)

0.35

3 (1.0)

 Limited prenatal care (< 5 visits)

83 (13.0)

11 (3.2)

< .001

8 (2.7)

< .001

2 (4.8)

0.011

72 (25.0)

 Gestational Diabetes

67 (10.5)

43 (12.4)

0.26

35 (11.8)

0.42

6 (14.3)

0.28

24 (8.3)