Table 1 Maternal and obstetric characteristics before propensity score matching

Maternal age,years

95,481

31.05 ± 5.28

32.569 ± 5.16

 < 0.001

0.28

31.07 ± 5.29

Gestational age at delivery,weeks

95,481

39.0 [38.0–40.0]

39.0 [38.0–40.0]

0.25

-0.01

39.0 [38.0–40.0]

Gravidity

96,766

2.0 (1.0–4.0]

3.0 [2.0–4.0]

 < 0.001

0.26

2.0 [1.0–4.0]

Parity

96,766

1.0 [0.0–2.0]

1.0 [1.0–2.0]

 < 0.001

0.21

1.0 [0.0–2.0]

Previous abortion

96,766

0.0 [0.0–1.0]

0.0 [0.0–1.0]

 < 0.001

0.19

0.0 [0.0–1.0]

Assisted reproductive technology

60,344

3309 (5.51)

23 (6.78)

0.30

0.05

3332 (5.52)

BMI < 18.5 kg/m²

20,878

1700 (8.24)

18 (6.84)

0.06

-0.05

1718 (8.22)

 ≥ 18.5 and < 25 kg/m²

12,611 (61.17)

145 (55.13)

-0.12

12,756 (61.09)

 ≥ 25 and < 30 kg/m²

4164 (20.19)

62 (23.57)

0.08

4226 (20.24)

 ≥ 30 and < 35 kg/m²

1489 (7.22)

24 (9.12)

0.06

1513 (7.24)

 ≥ 35 kg/m²

651 (3.15)

14 (5.32)

0.10

665 (3.18)

Previous cesarean aection

69,521

8379 (12.16)

93 (14.48)

0.07

0.06

8472 (12.18)

Hypertensive disorder of pregnancy (any)

96,722

2492 (2.59)

28 (3.80)

0.04

0.06

2520 (2.60)

Chronic hypertension

96,721

647 (0.67)

2 (0.27)

0.25

-0.05

649 (0.67)

Pre-eclampsia (any)

96,722

2194 (2.28)

16 (2.17)

0.84

-0.008

2210 (2.28)

Mild pre-eclampsia

96,721

574 (0.59)

4 (0.54)

 > 0.999

-0.007

578 (0.58)

Severe pre-eclampsia

96,721

576 (0.6)

2 (0.27)

0.33

-0.05

578 (0.59)

Pre-gestational diabetes

96,722

648 (0.67)

5 (0.67)

0.82

0.0

653 (0.67)

Gestational diabetes

96,723

6232 (6.4)

56 (7.59)

0.22

0.04

6288 (6.50)

Oligohydramnion

96,722

2507 (2.61)

23 (3.12)

0.38

0.03

2530 (2.61)

Polyhydramnion

96,721

1186 (1.23)

9 (1.22)

0.97

-0.001

1195 (1.23)

Stillbirth history

96,721

418 (0.43)

13 (1.76)

 < 0.001

0.12

431 (0.44)

Gender (male)

96,759

49,873 (51.15)

459 (58.85)

 < 0.001

-0.15

50,332 (51.22)