Table 1 Basic characteristics and potential risk factors of the study participants in the two study groups

Present conditions

Advanced maternal age

59(26.9)

27(22.5)

0.369^a

Pre-pregnancy BMI

21.5 ± 3.2

21.2 ± 2.5

0.326^b

Gravidity

4(3–5)

3(2–5)

0.004^c

Gravidity > 3

137(62.6)

52(43.3)

< 0.001^a

Parity

1(1–2)

1(1–2)

0.122^c

Parity > 1

76(34.7)

35(29.2)

0.299^a

Nulliparous women

6(2.7)

10(8.3)

0.020^a

Multiple gestation

10(4.6)

8(6.7)

0.409^a

In vitro fertilization

9(4.1)

8(6.7)

0.302^a

Placenta previa

203(92.7)

85(70.8)

< 0.001^a

Placenta location

< 0.001^a

 Anterior

145(66.2)

34(28.3)

 Posterior

57(26.0)

78(65.0)

 bilateral/fundal

17(7.8)

8(6.7)

Pregnancy complications

35(16.0)

11(9.2)

0.080^a

Adenomyosis/current fibroids

10(4.6)

6(5.0)

0.857^a

Mullerian anomaly

3(1.4)

3(2.5)

0.670^d

Severity of invasion

< 0.001^a

 Noninvasive (accreta)

56(25.6)

89(74.2)

 Invasive (increta/percreta)

163(74.4)

31(25.8)

Delivery mode

< 0.001^d

 Vaginal/operative vaginal

0(0)

4(3.3) ^e

 Planed CD

217(99.1)

81(67.5)

 Emergency CD

2(0.9)

35(29.2)

Delivery gestational weeks

35.0(34.2–35.5)

37.4(35.5–39.1)

< 0.001^c

Previous conditions

History of previous CD

189(86.3)

79(65.8)

< 0.001^a

History of clinical confirmed PAS

14(6.4)

25(20.8)

< 0.001^a

History of endometrial ablation

1(0.5)

2(1.7)

0.287^d

Previous uterine artery embolization for PPH

7(3.2)

6(5.0)

0.395^d

History of myomectomy

0(0.0)

2(0.9)

NA

History of operative hysteroscopy

8(3.7)

10(8.3)

0.066^a

History of intrauterine adhesions (IUA)

7(3.2)

13(10.8)

0.004^a

Dilation and evacuation of the uterus

17(7.8)

12(10.0)

0.481^a

History of placenta previa

11(5.0)

11(9.2)

0.139^a

Previous manual removal of placenta/placenta retention

8(3.7)

12(10.0)

0.018^a