Table S3.Changes inestimated blood loss (according to groups and sub-groups of riskfactors as appropriatetopre-pregnancy,during 
pregnancy,labourandbirth),principalpredictors ofpostpartum haemorrhage (PPH)>500mland conditional predictors ofprogressionto
severe PPH >1500ml;unadjusted associations. 
  OddsRatio(OR)(95%CI)
Predictive variable Mean changein EBL (ml) 
 
Allwomen 
>500ml 
 
Allwomen 
>1500ml 
 
Women with PPH>500 ml 
Group A:Pre-pregnancy
Sub-group i:Age 
Age for each10 years 67  (38 to97) 1.46 (1.21 to 1.77) 0.97 (0.76 to1.25)
Ethnicity 
White (referencegroup)    
BlackBritish -53 (-152 to46) 0.46 (0.20 to 1.06) 2.01 (0.69 to5.84)
BlackCaribbean -48 (-125 to29) 1.01 (0.57 to 1.78) 0.47 (0.21 to1.03)
BlackAfrican 128 (64 to192) 1.68 (1.23 to 2.28) 1.13 (0.76 to 1.69)
Bangladeshi -78 (-170 to14) 0.56 (0.22 to 1.46) 0.62 (0.15 to2.52)
Indian  117 (-33to267) 1.40 (0.73 to 2.67) 1.44 (0.45 to4.64)
Pakistani 45 (-39 to129) 1.13 (0.62 to 2.04) 1.09 (0.45 to2.64)
Chinese 237 (34 to441) 2.54 (0.73 to 8.82) 1.25 (0.46 to3.41)
Other Asian 88 (-175to351) 1.35 (0.38 to 4.75) 0.73 (0.17 to3.04)
Mixed -96 (-174 to-19) 0.59 (0.26 to 1.33) 0.52 (0.15 to 1.76)
Other/unknown 90 (1 to180) 1.01 (0.60 to 1.71) 1.27 (0.70 to 2.30)
Sub-group ii:Local deprivation  
IMD*:most deprived quintile 4(-35 to43) 1.00 (0.80 to 1.26) 0.96 (0.69 to 1.34)
Barriers tohousing & services 61 (22 to100) 1.29 (1.02 to 1.62) 0.87 (0.64 to1.20)
Education, skills and training -63(-126 to0) 0.57 (0.39 to 0.85) 1.98 (1.18 to 3.32)
Sub-group iii:General riskfactors
Current smoker -82 (-142 to -22) 0.74 (0.51 to 1.07) 0.48 (0.29 to0.80)
BMI perunit (Kg/m2) 6(1to10) 1.01 (0.99 to 1.04) 1.04 (1.01 to1.07)
Anaemia (iron at first appointment) 6(-151 to163) 0.76 (0.24 to 2.43) 1.31 (0.35 to4.95)
Essentialhypertension 172 (-73to417) 2.09 (0.67 to 6.55) 0.40 (0.11 to1.45)
Diabetes 34 (-121to189) 1.31 (0.40 to 4.25) 0.91 (0.26 to3.17)Depression -49 (-128 to29) 0.80 (0.39 to 1.64) 0.77 (0.31 to1.89)
Epilepsy 46 (-120to212) 1.76 (0.33 to 9.44) 1.04 (0.22 to4.99)
Lupus -102 (-442 to 238) 0.48 (0.05 to 4.61) # 
Fibroids 116 (3 to229) 1.60 (0.94 to 2.70) 0.87 (0.51 to1.50)
FGM 75 (-32 to181) 1.15 (0.60 to 2.19) 1.59 (0.83 to3.08)
Clotting/thrombotic disorders 189 (-32to411) 3.14 (0.91 to 10.90) 0.86 (0.32 to2.32)
Uterine anomaly -26 (-365 to312) 1.44 (0.13 to 15.66) 0.82 (0.07 to 9.79)
Planned pregnancy 36 (-6 to78) 1.06 (0.82 to 1.38) 1.35 (0.95 to 1.92)
Assistedconception 234 (107 to360) 3.80 (1.69 to 8.57) 1.26 (0.63 to2.54)
Gestationat booking 0(-3 to3) 1.00 (0.98 to 1.01) 0.98 (0.96 to1.01)
Sub-group iv:Obstetrichistory 
Previous PPH 164 (7 to320) 1.52 (0.86 to 2.68) 1.85 (1.01 to3.40)
Number of previous PPH 153 (22 to284) 1.62 (0.99 to 2.64) 1.57 (0.95 to2.59)
Previous caesarean section 195 (118 to273) 2.80 (2.00 to 3.94) 0.68 (0.43 to 1.05)
Parity(using0asreference group)    
1 -73 (-119 to-27) 0.64 (0.49 to 0.83) 1.18 (0.80 to1.74)
2 -96 (-150 to-41) 0.62 (0.44 to 0.89) 1.67 (1.02 to 2.74)
3+ -77 (-161 to 7) 0.58 (0.37 to 0.91) 1.34 (0.77 to 2.31)
Multiparity -80 (-118 to-42) 0.63 (0.50 to 0.79) 1.33 (0.97 to1.83)
Group B:Pregnancy 
Sub-group v:Current pregnancy
Multiple pregnancy 208 (90 to326) 2.15 (1.05 to 4.41) 1.47 (0.80 to 2.70)
Number of fetuses 215 (100 to330) 2.18 (1.11 to 4.29) 1.44 (0.82 to 2.53)
Antenataladmissions 42 (-10 to94) 1.37 (1.01 to 1.87) 0.84 (0.58 to 1.23)
Admissions >24/40 54 (0 to107) 1.52 (1.10 to 2.09) 0.80 (0.54 to 1.18)
Sub-group vi:Antenatal day unit(ADU)
Any ADU attendance 49 (11 to87) 1.28 (1.02 to 1.60) 1.25 (0.91 to1.72)
>1 ADUattendance 27 (6 to49) 1.15 (1.01 to 1.31) 1.08 (0.92 to1.27)
Abdominalpain 11 (-35 to57) 1.10 (0.81 to 1.50) 0.91 (0.63 to1.31)
IM iron 512 (493 to531) # # 
Itching 39 (-76 to155) 1.13 (0.54 to 2.40) 1.20 (0.55 to2.63)
Pre-eclampsia screen 81 (12 to150) 1.62 (1.07 to 2.43) 0.90 (0.59 to1.37)Growthscan 33 (-190to256) 0.40 (0.12 to 1.31) 1.64 (0.35 to7.81)
Generally unwell(nodiagnosis) 132 (13 to251) 1.22 (0.66 to 2.23) 2.30 (1.09 to4.88)
ADUforAPH (noadmission) 53 (-56 to163) 0.99 (0.56 to 1.74) 1.60 (0.87 to2.92)
Sub-group vii:Placentapraevia
Placenta praevia 1270 (410to2130) 7.74 (1.02 to 58.41) 4.86 (1.99 to11.87)
Majorplacenta praevia 1931 (525to3336) NA 3.67 (1.26 to10.71)
Minorplacenta praevia 477 (-41to996) 2.56 (0.30 to 21.59) 6.66 (1.25 to35.39)
Anteriorplacenta praevia 2909 (1150 to4669) NA 12.30(4.49 to 33.72)
Posterior placenta praevia 564 (61 to1068) 4.81 (0.59 to 38.89) 2.41 (0.74 to7.86)
Sub-group viii:APHand UTI 
APH 172 (15 to329) 1.36 (0.78 to 2.37) 1.96 (1.15 to3.34)
‘Warning’ APH 1145 (325to1965) 7.26 (0.96 to 55.16) 4.10 (1.65 to10.20)
Urinarytract infection 20 (-41 to80) 1.08 (0.73 to 1.60) 1.12 (0.69 to1.82)
Sub-group ix:Pre-eclampsiaand anaemia
Gestationalhypertension 131 (10 to252) 2.28 (1.15to 4.54) 0.74 (0.39 to1.41)
Pre-eclampsia (all) 219 (113 to326) 4.63 (1.79 to 11.96) 0.76 (0.39 to 1.50)
Pre-eclampsia <34/40 235 (17 to452) 6.44 (0.81 to 51.41) 0.73 (0.21 to 2.51)
Pre-eclampsia >34/40 212 (92 to333) 4.12 (1.41 to 11.98) 0.78 (0.35 to1.72)
Anaemia <10.5 g/ml 40 (-20 to101) 1.15 (0.83 to 1.60) 1.27 (0.84 to1.92)
Anaemia <11.1 g/ml 5(-39 to50) 1.00 (0.79 to 1.28) 1.05 (0.74 to1.48)
Polyhydramnios 75 (-178 to328) 0.29 (0.03 to 2.90) 6.57 (0.41 to105.69)
Sub-group x: Medicationspre-birth (in the weekbeforebirth)
Antibiotics 52 (5 to98) 1.35 (1.02 to 1.80) 1.08 (0.76 to 1.53)
Antihypertensives (includingfor 
Pre-eclampsia) 
105 (27 to182) 1.76 (1.11 to 2.78) 0.79 (0.50 to 1.27)
Aspirin 129 (14 to244) 1.50 (0.81 to 2.81) 1.02 (0.55 to1.91)
Medicationfordiabetes 100 (-44to244) 2.62 (1.04to 6.57) 0.91 (0.42 to2.00)
Steroids forfetalreasons  106 (12 to201) 1.17 (0.77 to 1.79) 2.06 (1.25 to3.40)
Oraliron 23 (-25 to70) 1.08 (0.82 to 1.44) 1.40 (0.99 to2.00)
Steroids formaternalreasons 53 (-65 to170) 1.17 (0.59 to 2.33) 1.67 (0.69 to 4.02)
Painrelief 154 (27 to281) 1.62 (0.73 to 3.58) 1.38 (0.65 to2.91)
Threatened preterm labour 246 (-220 to712) 1.77 (0.59 to 5.31) 0.65 (0.21 to2.04)
Thyroid disease 241 (-99 to581) 1.55 (0.65 to 3.71) 2.04 (0.75 to5.57)Group C:Labourandbirth 
Sub-group xi:Gestation at birth 
Gestationalage at birth 0(-9 to9) 1.03 (0.98 to 1.09) 0.96 (0.91 to1.02)
Sub-group xii:Birth weight
Maximum birthweight (Kg) 50 (15 to85) 1.50 (1.22 to 1.85) 1.06 (0.83 to 1.35)
Totalbirthweight (Kg) 69 (38 to101) 1.55 (1.27 to 1.89) 1.16 (0.93 to1.44)
Macrosomia >4 Kg 128 (55 to201) 1.94 (1.33 to 2.82) 1.21 (0.76 to 1.95)
Macrosomia >4.5 Kg 156 (31 to281) 2.96 (1.19 to 7.36) 0.81 (0.38 to1.71)
Sub-group xiii:Onsetoflabour
Spontaneous onset (referencegroup)
Augmented 113 (14 to211) 1.96 (1.19 to 3.24) 1.21 (0.57 to2.58)
Induced 100 (50 to150) 1.90 (1.39 to 2.60) 0.89 (0.60 to1.33)
None (prelabour caesarean) 262 (202 to323) 5.07 (3.41 to 7.53) 0.56 (0.38 to0.84)
DurationofROM(days) 65 (28 to102) 1.54 (1.20 to 1.99) 0.93 (0.70 to 1.23)
DurationofROMunrecorded 280 (219-341) 6.29 (4.28to 9.54) 0.42 (0.25 to0.68)
Prostin  54 (5 to104) 1.43 (1.04 to 1.96) 0.98 (0.66 to1.45)
Sub-group xiv:Intrapartum 
Syntocinon  137 (92 to183) 2.40 (1.84 to 3.14) 0.81 (0.58 to1.14)
DurationofSyntocinon 
(hours) 
10 (0 to19) 1.06 (1.00 to 1.13) 1.03 (0.98 to1.08)
Spinal anaesthesia 181 (137 to226) 4.10 (2.93 to 5.75) 0.37 (0.25 to0.54)
Epiduralanalgesia  159 (117 to202) 2.91 (2.22 to 3.81) 0.71 (0.52 to0.97)
Temperature    
Temperature>37.2°C 190 (127 to252) 2.65 (1.86 to 3.77) 0.92 (0.62 to 1.38)
Temperature>37.5°C 282 (169 to396) 4.60 (2.34 to 9.06) 1.12 (0.64 to1.95)
Temperature>37.8°C 413 (234 to592) 7.94 (2.48 to 25.43) 1.31 (0.62 to2.78)
Temperature>38.0°C 724 (368 to1080) 132.72 (17.53to 1004.68) 2.49 (0.92 to6.69)
Alltemperature> 37.0°C 686 (412 to960) 47.99 (7.16to 321.46) 1.66 (0.71 to3.89)
Temperatureunrecorded 41 (-2 to84) 1.28 (1.00 to 1.65) 0.73 (0.53 to1.01)
Evidence of chorioamnionitis 796 (261 to1330) NA 4.65 (1.09 to19.89)
Sub-group xv:Birth 
Mode ofbirth-SVD (reference group)
Instrumentalvaginalbirth 194 (132 to255) 3.84 (2.71 to 5.44) 0.45 (0.29 to 0.70)Elective caesareansection 298 (238 to358) 8.95 (5.80 to 13.79) 0.20 (0.13 to0.33)
Emergencycaesareansection 409 (357 to461) 17.05 (11.47 to 25.34) 0.37 (0.25 to 0.55)
Sub-group xvi:Thirdstage 
Physiologicalthird stage  -177 (-223 to -130) 0.47(0.30 to 0.75) 3.18 (1.75 to 5.77)
Syntocinon IM 18 (-71 to106) 0.70 (0.44 to 1.11) 1.83 (0.83 to4.02)
Syntocinon IV(bolus) 317 (276 to359) 8.56 (6.42 to 11.41) 0.44 (0.32 to0.60)
Syntometrine IM -234 (-272 to -196) 0.19 (0.15 to 0.25) 1.63 (1.15 to 2.29)
Syntocinon IVincreased 36 (-23 to94) 1.10 (0.71 to 1.69) 0.71 (0.42 to1.18)
Syntocinon 40/50IU
infusioncommenced
272 (232 to313) 6.07 (4.64 to 7.92) 0.46 (0.34 to0.63)
Retained placenta 374 (154 to594) 3.49 (1.55 to 7.82) 1.76 (1.01 to3.06)
Intervaltosuturing (hours) 113 (14 to212) 0.97 (0.81 to 1.16) 1.44 (1.21 to 1.72)
Intervaltosuturing unknown 65 (-3 to133) 1.69 (1.05 to 2.72) 0.56 (0.32 to0.95)
Key:Forcontinuousmeasures (e.g. age,BMI)thechangeis givenforeachadditional10yearsofage or1kg/m2of BMI.  Forvariables withmorethan2
categories(e.g. ethnicity)areferencegroupisdeclared (White),andcomparisonsaremadetothis. *IMD;Index of multipledeprivation &two of seven 
subscalesbasedonarea of residence,EnglandandWalesshown. MethodsS1forfulllist. NA;Not applicable,allwomen hadEBL>500ml. #;numbers
too small. 
 
Summaryof significant factors: 
(a) Pre-pregnancy 
Beforeadjustingforpotentialconfounders, significantpre-pregnancy predictorsforPPHwere age, Black African ethnicity, index ofmultipledeprivation
(barrierstohousing&services), assistedconceptionandpreviouscaesarean,with indexofmultiple deprivation (education,skills andtraining)and
multiparity beingprotective.  Significant riskfactorsforprogression toseverePPHwereindexof multipledeprivation (education, skills andtraining),
BMI, previous PPHandparity (=2), withsmokingbeingprotective. 
(b) During pregnancy  
Predictors of PPHbeforeadjustment includedmultiple pregnancy,antenatalday unitattendance, antenataladmission, placentapraevia,gestational
hypertension,pre-eclampsia screen anddiagnosis, useofantibiotics, antihypertensives anddiabetesmedication.  Predictors ofprogression tosevere
PPHacquiredduringpregnancywereantenatalday attendancewith‘generally unwell(nodiagnosis)’, placentapraevia (major,minorandanterior),APH, 
‘warning’APHandsteroidsforfetalreasons.  
(c) Labourandbirth 
Labourand birthpredictorsof PPHincluded birthweight(Kg)andmacrosomia,nolabouronset, induction, augmentation,duration of ruptured
membranes, useofProstinandSyntocinon,regionalanalgesia andanaesthesia, temperature>37.00C, instrumentaldelivery,caesarean (electiveand
emergency),thirdstageSyntocinon IVbolus orinfusionandretainedplacenta. Unrecordedtemperature,duration of rupturedmembranesandinterval
to suturingwereallpredictors ofPPH. BothphysiologicalthirdstagemanagementandSyntometrine IMwereprotective. Intrapartumpredictorsof
progression to severePPHwereevidence of chorioamnionitis,physiologicalthirdstage management, SyntometrineIM, retainedplacentaandintervalto suturing. Protectivefactors includednolabouronset, regionalanalgesia andanaesthesia,instrumentaldelivery, caesarean(electiveandemergency)
and thirdstage Syntocinon IVbolusandinfusion.Unrecordeddurationof rupturedmembranesorintervaltosuturingappearedprotective