Association between oxytocin during labour and the risk of severe PPH according to prophylactic administration of oxytocin after delivery: women with no prophylactic oxytocin administration after delivery
| Women with severe PPH (n=593), n (%) | Controls (n=518), n (%) | Crude OR (95% CI) | Adjusted OR* (95% CI) | |
| Oxytocin during labour | 413 (70) | 256 (49) | 2.3 (1.8 to 3.0) | 1.8 (1.3 to 2.6) |
| Oxytocin total dose (IU)† | ||||
| Mean (SD) | 2.3 (2.3) | 1.5 (4.5) | ||
| No oxytocin | 180 (31) | 262 (53) | Ref | Ref |
| <1 | 155 (26) | 124 (25) | 1.8 (1.3 to 2.5) | 2.0 (1.3 to 2.9) |
| 1.0–<2.0 | 79 (13) | 63 (13) | 1.8 (1.2 to 2.7) | 1.4 (0.8 to 2.4) |
| 2.0–<4.0 | 101 (17) | 30 (6) | 4.9 (3.1 to 7.7) | 3.3 (1.8 to 5.9) |
| ≥4.0 | 74 (13) | 12 (2) | 9.0 (4.7 to 17.0) | 5.7 (2.5 to 12.9) |
| Maximal infusion rate (mIU/min)† | ||||
| Mean (SD) | 9.4 (5.8) | 8.0 (5.2) | ||
| No oxytocin | 180 (31) | 262 (54) | Ref | Ref |
| <7.5 | 138 (23) | 101 (21) | 2.0 (1.4 to 2.7) | 1.9 (1.2 to 2.9) |
| 7.5–<10 | 83 (14) | 48 (10) | 2.5 (1.7 to 3.8) | 1.8 (1.1 to 3.1) |
| 10–<15 | 99 (17) | 52 (11) | 2.8 (1.9 to 4.1) | 2.2 (1.3 to 3.8) |
| ≥15 | 88 (15) | 25 (5) | 5.1 (3.2 to 8.3) | 3.2 (1.7 to 6.1) |
| Total time of oxytocin infusion (min)† | ||||
| Mean (SD) | 288 (189) | 191 (137) | ||
| No oxytocin | 180 (30) | 262 (51) | Ref | Ref |
| <180 | 139 (23) | 137 (27) | 1.5 (1.1 to 2.0) | 1.7 (1.1 to 2.5) |
| 180–<300 | 102 (17) | 71 (14) | 2.1 (1.5 to 3.0) | 1.7 (1.0 to 2.7) |
| 300–<420 | 76 (13) | 26 (5) | 4.3 (2.6 to 6.7) | 3.2 (1.6 to 6.1) |
| ≥420 | 96 (16) | 16 (3) | 8.7 (5.0 to 15.3) | 5.1 (2.4 to 10.6) |
| Time at maximal infusion rate (min)† | ||||
| Mean (SD) | 128 (107) | 96 (89) | ||
| No oxytocin | 180 (31) | 262 (56) | Ref | Ref |
| <90 | 178 (31) | 121 (26) | 2.1 (1.6 to 2.9) | 1.9 (1.2 to 2.8) |
| 90–<150 | 87 (15) | 48 (10) | 2.6 (1.8 to 3.9) | 2.0 (1.2 to 3.5) |
| 150–<210 | 48 (8) | 17 (4) | 4.1 (2.3 to 7.4) | 2.7 (1.3 to 5.7) |
| ≥210 | 79 (14) | 22 (5) | 5.2 (3.1 to 8.7) | 2.6 (1.3 to 5.1) |
PPH, postpartum haemorrhage.
↵* Multilevel logistic regression models adjusted for body mass index, parity, induction of labour, epidural analgesia, duration of the active phase of the first stage of labour, duration of expulsive efforts, operative delivery, episiotomy, perineal tear and birth weight.
↵† The thresholds correspond to the 50th, 75th and 90th percentiles of their distribution in the control group rounded to the nearest whole number.