Table 1 The patients’ characteristics

Number of vaginal deliveries (times)

None

36(61.02)

41(71.93)

—

0.304*

1

19(32.20)

11(19.30)

2

4(6.78)

5(8.77)

Number of abdominal surgeries (times)

None

37(62.71)

31(54.39)

χ² = 0.83

0.363

1

22(37.29)

26(45.61)

Age (year)

36.46 ± 10.04

34.67 ± 8.64

t = 1.03

0.306

BMI (kg/m²)

21.84 ± 2.04

21.69 ± 2.29

t = 0.37

0.711

ASA classification

I

39(66.10)

36(63.16)

χ² = 0.11

0.740

II

20(33.90)

21(36.84)

Operating table tilt angle (°)(Median [IQR])

29.00(20.00,30.00)

30.00(20.00,30.00)

Z = 0.28

0.780#

Complications

Hypertension

4(6.78)

1(1.75)

χ² = 0.77

0.382

Chronic carriers of hepatitis B virus

2(3.39)

6(10.53)

χ² = 1.32

0.250

Pulmonary tuberculosis

1(1.69)

0(0.00)

—

1.000*

Diabetes

1(1.69)

0(0.00)

—

1.000*