Table 3 Risk factors for large volume transfusion (≥4 unit transfusion) among 228,884 pregnancies

RR(95% CI)

RR(95% CI)

Maternal age

Under 20

1.3 (0.96,1.77)

1.43 (1.05,1.93)

20-34

ref

ref

35+

1.56 (1.35,1.79)

1.38 (1.2,1.59)

Maternal Country of birth

Australia/NZ

ref

ref

Asia

1.35 (1.15,1.59)

1.39 (1.18,1.63)

Other

0.94 (0.79,1.13)

0.97 (0.81,1.16)

Multiple pregnancy

2.21 (1.63,2.98)

1.72 (1.25,2.36)

Morbid Obesity

2.13 (1.15,3.93)

1.54 (0.74,3.19)

Smoking during pregnancy

1.37 (1.15,1.62)

1.22 (1.02,1.45)

Chronic conditions

3.51 (2.72,4.54)

3.15 (2.43,4.09)

Assisted Reproductive technology

2.04 (1.47,2.83)

1.61 (1.18,2.2)

Previous PPH

9.66 (8.5,10.97)

8.36 (7.33,9.53)

Uterine surgery (5 years)

2.24 (1.03,4.87)

2.4 (1.14,5.01)

Uterine fibroids (1 year)

3.12 (1.42,6.85)

2.29 (1.06,4.98)

Parity

Primiparous

ref

ref

Multiparous no previous CS^a

0.65 (0.56,0.75)

0.71 (0.62,0.83)

Multiparous, previous CS^a

1.25 (1.05,1.49)

1.29 (1.08,1.54)

Low socioeconomic status

1.25 (1.09,1.44)

1.25 (1.08,1.44)

Placenta Praevia

9.27 (7.53,11.43)

Pregnancy hypertension

1.49 (1.23,1.79)

Induction

1.3 (1.13,1.49)

Placental abruption

7.01 (5.17,9.49)

Gestation (weeks)

20-32

1.65 (1.27,2.15)

33-36

1.47 (1.2,1.8)

37+

ref