Table 2 Background information on the study groups

Previous pregnancy

FOC

1709

13.1 (12.5–13.7)

1897

1.0 (0.9–1.0)

Mode of delivery in first pregnancy

Spontaneous vaginal

3861

30.0 (28.6–30.5)

134 462

68.8 (68.5–69.2)

Vacuum

2787

21.3 (20.6–22.1)

28 485

14.6 (14.4–14.8)

Breech or forceps

82

0.6 (0.5–0.8)

1721

0.9 (0.8–0.9)

Unplanned caesarean section

4034

30.9 (29.9–31.9)

20 050

10.3 (10.1–10.4)

Emergency caesarean section

722

5.5 (5.1–5.9)

2343

1.2 (1.2–1.2)

Elective caesarean section

1579

12.1 (11.5–12.7)

8282

4.2 (4.1–4.3)

Obstetric challenges

Uterine curettage

167

1.3 (1.1–1.5)

1581

0.8 (0.8–0.9)

Manual placenta removal

274

2.1 (1.9–2.4)

2945

1.5 (1.5–1.6)

Third- or fourth-degree tears of the perineum

458

3.5 (3.2–3.8)

2539

1.3 (1.3–1.4)

Shoulder dystocia^a

74

0.6 (0.4–0.7)

425

0.2 (0.2–0.2)

Adverse neonatal outcomes

Very or extremely preterm delivery (< 31 + 6 weeks)

74

0.6 (0.4–0.7)

1147

0.6 (0.6–0.6)

Need for intensive care unit^a

1079

8.3 (7.8–8.8)

16 022

8.2 (8.1–8.3)

Neonatal mortality^b

112

0.9 (0.7–1.0)

899

0.5 (0.4–0.5)

The second pregnancy

Age (mean; SD)

31.2 (4.8)

29.8 (4.8)

Smoking status smoker

1524

11.7 (11.1–12.3)

20 988

10.7 (10.6–10.9)

Maternal BMI (kg/m²) (mean; SD)

25.1 (5.2)

24.5 (4.9)

Maternal gestational diabetes

2321

17.8 (17.1–18.5)

25 255

12.9 (12.8–13.1)

Neonatal weight, grams (mean; SD)

3620 (459)

3591(515)

Induction of labour

2495

19.1 (18.4–19.9)

33 410

17.1 (16.9–17.3)

Length of pregnancy (week + day) (mean; SD)

39 + 4 (8)

39 + 6 (6)

preterm (< 37 gestational weeks)

258

2.0 (1.7–2.2)

7046

3.6 (3.5–3.7)