Table 1 Profile of studies entered into systematic review and meta-analysis

Yu SCH, 2020, [26]

Maternal age (years)

35.3 [31.5-37.6]

36.6 [32.7-39.1]

-

Sample size (n)

20

20

-

Intraoperative blood loss (mL)

1451 [1024-2388]

1454 [888-2300]

0.945

Blood transfusion (units)

0.5 [0-2.75]

2 [0-4]

0.55

Gestation (weeks)

36.6 [35.2-37.2]

36.1 [34.8-37.7]

0.968

Hysterectomy (%)

0.0

0.0

-

Sallam, 2018, [27]

Maternal age (years)

29.71±2.84

29.68± 2.53

-

Sample size (n)

62

62

-

Intraoperative blood loss (mL)

1151.61±246.38

1800±980

0.0001

Gestation (weeks)

35.55±0.77

35.58±0.62

0.977

Darwish, 2014, [28]

Maternal age (years)

33.8

33.5

-

Sample size (n)

32

32

-

Intraoperative blood loss (mL)

1900

2800

0.019

Blood transfusion (units)

2.9

4.7

0.142

Gestation (weeks)

35.6

34.3

0.008

Omar, 2017, [29]

Maternal age (years)

34.7±6.8

33.1±5.9

-

Sample size (n)

20

20

-

Intraoperative blood loss (mL)

1076±545

1664±647

<0.001

Blood transfusion (units)

2

4

0.13

Hysterectomy (%)

5

10

0.41

Jiang, 2013, [30]

Sample size (n)

13

28

-

Intraoperative blood loss (mL)

1429±875

4600± 2090

0.000

Blood transfusion volume (ml)

920±438

3600± 1225

0.000

Hysterectomy (%)

84.61

89.28

0.670

Broekman, 2015, [31]

Maternal age (years)

32.6 ± 4.3

34.1 ± 3.7

-

Sample size (n)

42

26

-

Intraoperative blood loss (mL)

800 (488–1113)

1000 (694–1307)

0.06

Blood transfusion (units)

4

6

Gestation (weeks)

37 (36-38)

37(35-38)

0.16

Mei, 2018, [32]

Sample size (n)

20

12

-

Intraoperative blood loss (mL)

800 (500-1800)

1875 (500-7600)

0.01

Hysterectomy (%)

0.0

8.3

<0.01

Soyama, 2017, [33]

Maternal age (years)

35 (27–42)

34 (19–43)

-

Sample size (n)

50

216

-

Intraoperative blood loss (mL)

979 (287–2369)

2189 (2133–3360)

<0.01

Gestation (weeks)

36 (30-38)

37 (30-38)

0.87

Fan, 2017, [34]

Maternal age (years)

32.6±0.6

32.0±0.4

-

Sample size (n)

74

89

-

Intraoperative blood loss (mL)

1236.0±138.2

1694.0±144.3

0.01

Blood transfusion volume (ml)

728.0±113.6

1205.0±138.7

0.01

Gestation (weeks)

36.5±0.1

36.4±0.2

0.65

Hysterectomy (%)

2.7

5.6

0.36

Dai, 2018, [35]

Sample size (n)

42

20

-

Intraoperative blood loss (mL)

2900.00 ± 2352.21

4549.77 ± 2366.67

0.025

Blood transfusion (units)

8.40 ± 7.14

13.00 ± 7.93

0.018

Hysterectomy (%)

2.3

35

0.027

Ono, 2018, [36]

Maternal age (years)

33.7±3.8

34.0±3.9

-

Sample size (n)

29

13

-

Intraoperative blood loss (mL)

2027.1±1637.6

3786.7±2936.1

<0.01

Gestation (weeks)

34.8±1.5

35±2.2

<0.01

Bodner, 2006, [37]

Maternal age (years)

35.3

35.3

-

Sample size (n)

6

22

-

Intraoperative blood loss (mL)

2600

2800

0.4

Blood transfusion (units)

6.3

6.5

0.47

Gestation (weeks)

32.5

36.5

0.019

Picel, 2018, [38]

Sample size (n)

61

90

-

Intraoperative blood loss (mL)

2000 (1500-2500)

2500 (2000-4000)

0.002

Blood transfusion (units)

2 (0-5)

5 (2-8)

0.002

Wang, 2017, [39]

Sample size (n)

10

43

-

Intraoperative blood loss (mL)

1000

2000

<0.05

Hysterectomy (%)

10

63.3

<0.05

Peng, 2020, [40]

Maternal age (years)

32.08 ± 3.94

33.46 ± 4.53

-

Sample size (n)

48

56

-

Intraoperative blood loss (mL)

690.00 ± 226.88

887.10 ± 311.71

0.018

Blood transfusion volume (ml)

970.54 ± 1083.21

1352.08 ± 1211.03

0.093

Gestation (weeks)

35.57 ± 1.97

36.05 ± 1.66

0.177

Hysterectomy (%)

12.5

29.2

0.035

El-sayed, 2016, [41]

Maternal age (years)

33.54±4.36

33.62± 3.86

-

Sample size (n)

50

50

-

Intraoperative blood loss (mL)

850±20

1120±70

0.000

Blood transfusion (units)

1.8 ± 0.4

2.1 ± 0.5

0.001

Hysterectomy (%)

10

12

-

Wu, 2016, [42]

Maternal age (years)

29.5±3.6

30.4±4.0

-

Sample size (n)

230

38

-

Intraoperative blood loss (mL)

921±199

2790±335

0.000

Blood transfusion volume (ml)

422±58

1580±67

0.000

Gestation (weeks)

35.6±1.3

35.5±1.5

0.595

Hysterectomy (%)

0.0

7.89

0.003

Feng, 2017, [43]

Maternal age (years)

31.8±5.6

32.5±5.7

-

Sample size (n)

30

11

-

Intraoperative blood loss (mL)

1000(600-2500)

1100(800-2600)

0.64

Blood transfusion (units)

0(0-6)

3(0-8)

0.67

Gestation (weeks)

37 (36-37.28)

37.42(36.28-39)

0.069

Li, 2018, [44]

Maternal age (years)

34.53 ± 5.80

33.43 ± 4.32

-

Sample size (n)

112

87

-

Intraoperative blood loss (mL)

1850±490

3800±560

<0.001

Blood transfusion volume (ml)

480±220

2000±1120

<0.001

Gestation (weeks)

37.02 ± 1.3

36.78 ± 1.38

0.273

Hysterectomy (%)

11.61

32.18

<0.001

Cali, 2014, [45]

Sample size (n)

30

23

-

Intraoperative blood loss (mL)

846.67±280.06

1156.52±576.69

0.036

Blood transfusion volume (ml)

470±860

1960±246

0.011

Dai, 2020, [46]

Maternal age (years)

34.08 ± 4.75

32.59 ± 4.10

-

Sample size (n)

51

27

-

Intraoperative blood loss (mL)

1846 ± 2187

3717 ± 2717

<0.001

Blood transfusion (units)

5.65 ± 5.71

11.48 ± 8.72

<0.001

Gestation (weeks)

34.94 ± 1.49

34.07 ± 4.19

0.178

Hysterectomy (%)

2

11.1

0.081

Chou, 2015, [47]

Sample size (n)

13

11

-

Intraoperative blood loss (mL)

1902.3±578.8

4445.7±996.48

0.0402

Zhou, 2019, [48]

Maternal age (years)

32.31 ± 4.20

32.52 ± 4.32

-

Sample size (n)

58

25

-

Intraoperative blood loss (mL)

1215.52 ± 762.57

1602.00 ± 862.47

0.045

Blood transfusion volume (ml)

425.86 ± 667.43

832.80 ± 887.89

0.024

Gestation (weeks)

35.95 ± 0.31

35.83 ± 0.34

0.144

Hysterectomy (%)

6.9

12

0.445

Tan, 2017, [49]

Maternal age (years)

32 (27–37)

35 (29–43)

-

Sample size (n)

11

14

-

Intraoperative blood loss (mL)

2011 (400–5000)

3316 (1000–4000)

0.042

Blood transfusion volume (ml)

1058 (0–3600)

2211 (1190–3980)

0.005

Gestation (weeks)

36.2 (33–38)

35.7 (28.5–39)

-

McGinnis, 2019, [50]

Maternal age (years)

34 (24-44)

33 (26-37)

-

Sample size (n)

12

12

-

Intraoperative blood loss (mL)

2450 (1500-3125)

2750 (1875-3500)

0.28

Blood transfusion (units)

3.5 (2.2-5.5)

9.5 (4.2-12)

0.06

Gestation (weeks)

35 (27.9-37.7)

35 (27.9-37.7)

0.28

Panici, 2012, [51]

Maternal age (years)

29.4 ± 1.9

27.5 ± 1.7

-

Sample size (n)

15

18

-

Intraoperative blood loss (mL)

950(790-1100)

3375(2645-4007)

<0.001

Blood transfusion (units)

0 (0-1)

4 (3-5)

<0.001

Gestation (weeks)

36 ± 0.7

36 ± 0.6

-

Hysterectomy (%)

13

50

0.034

Cho, 2020, [52]

Maternal age (years)

34.5 ± 2.9

34.8 ± 3.3

-

Sample size (n)

17

25

-

Intraoperative blood loss (mL)

2319 (1000-4500)

4435 (1500-10500)

0.037

Blood transfusion volume (ml)

2060 (1200-8000)

3840 (1800-15200)

0.043

Hysterectomy (%)

29.4

44

0.339

Sun, 2018, [53]

Sample size (n)

19

12

-

Intraoperative blood loss (mL)

1200

3150

0.006

Blood transfusion volume (ml)

800

1950

0.017

Zeng, 2017, [54]

Maternal age (years)

32.27±5.27

33.13±5.23

-

Sample size (n)

48

38

-

Intraoperative blood loss (mL)

1467.71±1075.77

2218.42±1572.2

0.015

Blood transfusion (units)

5.42±4.95

9.29±7.59

0.008

Gestation (weeks)

36.04±2.18

35.41±2.42

0.205

Hysterectomy (%)

4.2

23.7

0.018