Table 1 Baseline characteristics

Maternal age

32.1 ± 4.8

32.0 ± 5.5

31.3 ± 5.6

36.1 ± 4.8

32.2 ± 5.2

0.088

BMI

24.6 ± 4.2

23.8 ± 3.7

25.6 ± 3.4

25.9 ± 4.1

24.5 ± 3.9

0.163

No maternal comorbidity

57 (61)

44 (56)

10 (50)

7 (70)

118 (58)

0.669

Caucasian ethnicity

60 (67)

53 (68)

12 (60)

7 (70)

132 (67)

0.914

African ethnicity

17 (19)

12 (15)

5 (25)

1 (10)

35 (18)

0.673

Education level^a: high

48 (87)

37 (80)

7 (58)

4 (67)

96 (81)

0.700

Education level^a: medium

4 (7)

8 (17)

4 (33)

2 (33)

18 (15)

0.058

Education level^a: low

3 (6)

1 (2)

1 (8)

0 (0)

5 (4)

0.106

Smoking during pregnancy

4 (5)

8 (11)

3 (16)

1 (10)

16 (8)

0.306

Drug use during pregnancy

7 (7)

4 (5)

2 (10)

0 (0)

13 (6)

0.677

Alcohol during pregnancy

1 (1)

0 (0)

1 (5)

0 (0)

2 (1)

0.241

Uterine malformation^b

2 (2)

5 (6)

0 (0)

0 (0)

7 (3)

0.320

Medical history of

- LLETZ/conization

12 (13)

18 (23)

1 (5)

6 (60)

36 (18)

0.000*

- Surgical curettage

6 (6)

2 (3)

4 (20)

0 (0)

12 (6)

0.023*

- Miscarriage < 8w

44 (47)

32 (41)

8 (40)

4 (40)

88 (43)

0.839

- Miscarriage 8-15w6d

9 (10)

5 (6)

0 (0)

2 (20)

16 (8)

0.227

- Miscarriage 16-23w6d

66 (70)

21 (27)

5 (25)

8 (80)

100 (49)

0.000*

- PTB 24-27w6d

19 (20)

5 (6)

2 (10)

3 (30)

29 (14)

0.027*

- PTB 28-33w6d

14 (15)

13 (17)

2 (10)

2 (20)

31 (15)

0.876

- PTB 34-36w6d

10 (11)

7 (9)

1 (5)

3 (30)

21 (10)

0.175

Gravidity

4 (1–10)

2 (1–9)

2 (1–8)

4 (2–12)

3 (1–12)

0.000*

Previous CD

26 (28)

24 (30)

4 (20)

3 (30)

57 (28)

0.833

Previous uterine rupture

0 (0)

1 (1)

1 (5)

0 (0)

2 (1)

0.221

Previous TVC 1x

37 (40)

3 (4)

0 (0)

5 (50)

45 (22)

0.000*

Previous TVC > 1

16 (17)

1 (1)

2 (10)

0 (0)

19 (9)

0.003*

Previous TAC only

0 (0)

2 (3)

0 (0)

1 (10)

3 (2)

0.063