Prospective study of intramuscular ergometrine compared with intramuscular oxytocin for prevention of postpartum hemorrhage

AIM: To compare the efficacy and safety of intramuscular oxytocin with intramuscular ergometrine in the management of postpartum hemorrhage during the third stage of labor. METHODS: Women who had been pregnant for more than 35 weeks and delivered cephalic singletons vaginally without predelivery administration of oxytocics were included. The cases considered to be at high risk were excluded, such as those who had uterine fibroids, a previous cesarean section, previous postpartum hemorrhage, or severe anemia. Five units of oxytocin or 0.2 mg of methylergometrine were administered intramuscularly immediately after delivery of the baby. RESULTS: Compared with intramuscular ergometrine, the use of intramuscular oxytocin was associated with a significant reduction in mean total postpartum blood loss (288.16 g vs 354.42 g, P = 0.004), frequency of postpartum hemorrhage (> or=500 mL: 10.9% vs 20.32%, relative risk [RR] = 0.54, 95% confidence interval [CI] = 0.32-0.91), and need for therapeutic oxytocics (5.13% vs 12.3%, RR = 0.42, 95% CI = 0.19-0.91). There were no differences between the groups in terms of the mean duration of the third stage, the mean level of hemoglobin on the second postpartum day, and the frequency of postpartum hemorrhage (> or =1000 mL), or manual removal of placenta. Few side-effects were found, with no significant differences between the groups. CONCLUSIONS: The routine use of intramuscular oxytocin is more effective than the use of intramuscular ergometrine for prevention of postpartum hemorrhage in the third stage of labor.     

A double-blinded, randomized controlled trial of oxytocin at the beginning versus the end of the third stage of labor for prevention of postpartum hemorrhage

OBJECTIVE: The objective of this study was to compare the administration of oxytocin at the beginning and end of the third stage of labor for the prevention of postpartum hemorrhage. METHODS: Patients with documented singleton pregnancies were randomly assigned to two groups. The first received 10 units of oxytocin intramuscularly at delivery of the anterior shoulder of the fetus and an identical appearing placebo injection following delivery of the placenta. The second received the opposite medication sequence. The study was double blinded. Blood loss was measured by weighing all fluids collected, visual estimation, and serial blood counts. RESULTS: 27 women received oxytocin at the delivery of the fetal shoulder and 24 after the placenta. Oxytocin given after placenta delivery resulted in lower blood loss (345 vs. 400 ml, p = 0.28), lower collection bag weight (763 vs. 833 g, p = 0.55), lower change in HgB (-1.26 vs. -1.32 g, p = 0.86), lower DeltaHCT (-3.43 vs. -3.64%, p = 0.85), and a shorter third stage of labor duration (8.6 vs. 9.2 min, p = 0.75). The incidence of postpartum hemorrhage, defined as estimated blood loss >500 ml (0 vs. 14.8%) was significantly lowered with oxytocin following placental delivery (p = 0.049). CONCLUSIONS: In our study, postpartum hemorrhage was less frequent when oxytocin administration was delayed until after placenta delivery.     

Misoprostol for prevention of postpartum hemorrhage.

OBJECTIVE: To compare the effectiveness of 400 microg rectal misoprostol in 5 cm(3) of saline with oxytocin 10 IU, i.m., in reducing bleeding during the third stage of labor. DESIGN: A double blind, randomized, clinical trial including 663 women with uncomplicated vaginal delivery who received misoprostol (n=324) or oxytocin (n=339). MAIN OUTCOME MEASURES: Changes in hemoglobin and hematocrit from before to 72 h postpartum; blood loss during the third stage; duration of the third stage of labor; need for additional oxytocic drug; frequency of requisition and of administration of blood; changes in blood pressure; and occurrence of side effects. RESULTS: No significant differences were observed between groups, before and 72 h postpartum, in mean hemoglobin and hematocrit, on volume of blood loss and duration of third stage of labor. The incidence of shivering and mean temperature (P<0.01) was significantly greater among women receiving misoprostol than oxytocin. CONCLUSIONS: Misoprostol administered as a micro-enema, 400 microg in 5 ml of saline during the third stage of labor, appears to be as effective as oxytocin 10 IU, i.m., but misoprostol produced more side effects than oxytocin.     

Effect of oxytocics on the blood pressure of normotensive Nigerian parturients.

BACKGROUND: The single most common direct obstetric disorder accounting for 25% of all maternal deaths globally is severe hemorrhage, generally occurring postpartum. Nearly all these deaths occur in the developing world. The role of oxytocic drugs in the management of the third stage of labor as a strategy to reduce maternal mortality has been emphasized. However, the adverse effects of these oxytocic agents, in particular ergometrine, have not been properly evaluated in our environment. OBJECTIVES: To evaluate the effect of ergometrine and oxytocin on the cardiovascular system when used for active management of the third stage of labor. STUDY DESIGN: A double-blind, randomized controlled study was carried out at the Federal Medical Centre, Makurdi over 24 months. Five hundred and ten patients were randomized to treatment with either 0.5 mg of intramuscular ergometrine or 10 IU of intravenous oxytocin, respectively, as single injections. Their effects on the cardiovascular system were observed using blood pressure as a marker. RESULTS: Ergometrine unlike oxytocin was observed to cause a significant rise in blood pressure, and this effect was most marked in the first 24 hours of the puerperium. CONCLUSIONS: These results suggest that ergometrine may be safe in normotensive parturients but hazardous in hypertensive parturients in whom oxytocin would be a safer option.     

A randomised controlled trial of intramuscular syntometrine and intravenous oxytocin in the management of the third stage of labour

Objective To compare the efficacy and safety of intravenous oxytocin with intramuscular syntometrine in the management of the third stage of labour
Design A prospective randomised trial
Setting A university teaching hospital
Methods A total of 991 women having a singleton pregnancy and vaginal delivery were randomised by a computer-generated number to receive either 1ml syntometrine intramuscularly or 10 units of intravenous Syntocinon after delivery of the anterior shoulder of the fetus
Main outcome measures Blood loss during delivery, rate of postpartum haemorrhage, need for repeated oxytocics, haemoglobin level before and 24 hours after delivery, duration of third stage, need for manual removal of placenta and sides effects including hypertension, nausea, vomiting, headache and chest pain
Results The use of intravenous oxytocin was associated with a reduction in postpartum blood loss (   P < 0.001  ) but there was no difference in the risk of postpartum haemorrhage in the need for repeated oxytocic injections and the drop in peripartum haemoglobin level between the two groups. There was also no difference in the risk of prolonged third stage, or in the need for manual removal of placenta. The use of syntometrine was associated with a higher risk of hypertension (RR 2.39, 95% CI 1.00–5.70). Other side effects were mild in nature with no differences between the two groups
Conclusions There are no important clinical differences in the effectiveness of intramuscular syntometrine and intravenous oxytocin for the prevention of postpartum blood loss. Intravenous oxytocin is less likely to cause hypertension     

A randomized controlled trial comparing oxytocin administration before and after placental delivery in the prevention of postpartum hemorrhage

OBJECTIVE: To determine if the timing of the administration of prophylactic oxytocin influences the incidence of postpartum hemorrhage caused by uterine atony, retained placenta, and third-stage duration. STUDY DESIGN: Parturients who presented for vaginal delivery were randomized in a double-blinded fashion to receive oxytocin, 20 units in a 500-mL crystalloid intravenous bolus, beginning upon delivery of either the fetal anterior shoulder or placenta. For all patients, the third stage of labor was managed with controlled cord traction until placental expulsion, followed by at least 15 seconds of fundal massage. Patients were excluded if they had a previous cesarean section, multiple gestation, antepartum hemorrhage, or bleeding disorder. RESULTS: A total of 1486 patients were enrolled: 745 in the before-placenta group and 741 in the after-placenta group. The groups were similar with respect to gestational age, fetal weight, labor duration, maternal age, parity, and ethnicity. The incidence of postpartum hemorrhage did not differ significantly between the two groups (5.4% vs 5.8%; crude OR, 0.92; 95% CI, 0.59 to 1.43). There were no significant differences between the two groups with respect to incidence of retained placenta (2.4% vs 1.6%; OR, 1.49; 95% CI, 0.72 to 3.08), or third-stage duration (7.7 minutes vs 8.1 minutes; P =.23). CONCLUSIONS: The administration of prophylactic oxytocin before placental delivery does not reduce the incidence of postpartum hemorrhage or third-stage duration, when compared with giving oxytocin after placental delivery. Early administration, however, does not increase the incidence of retained placenta.     

A prospective cohort study of oxytocin plus ergometrine compared with oxytocin alone for prevention of postpartum haemorrhage

Objective To determine the safety and efficacy of intramuscular oxytocin plus ergometrine compared to intravenous oxytocin for prevention of postpartum haemorrhage, and the significance of administration at the end of the second stage of labour compared with that after the third stage.
Design A prospective cohort study.
Setting A university affiliated tertiary medical centre.
Participants Two thousand one hundred and eighty–nine women delivering singletons during 40 consecutive weeks.
Main outcome measures Postpartum haemorrhage (> 500 ml), prolonged third stage (> 30 min), retained placenta (>60min), elevated blood pressure (systolic > 150 mmHg, diastolic > 100 mmHg).
Results The rate of postpartum haemorrhage was not significantly different for oxytocinergometrine compared with oxytocin, when administered at the end of the second stage of labour (odds ratio 1.10, 95% confidence interval (CI) 0.75–1.61) or after the third stage (odds ratio 0.95, 95% CI 0.68–1.34). The patients receiving oxytocics at the end of the second stage of labour had significantly lower rates of postparturn haemorrhage, for both oxytocinergometrine (odds ratio 0.69, 95% CI 0.49–0.98) and oxytocin (odds ratio 0.60, 95% CI 0.41–0.87), compared with those treated after the third stage.
Conclusion Administration of oxytocin alone is as effective as the use of oxytocin plus ergometrine in the prevention of postpartum haemorrhage, but associated with a significantly lower rate of unpleasant maternal side effects. Oxytocics administered after delivery of the fetal head compared with after the placental expulsion are associated with a significantly lower rate of postpartum haemorrhage.     

A randomised trial of carbetocin versus syntometrine in the management of the third stage of labour

OBJECTIVE: Syntometrine is an effective uterotonic agent used in preventing primary postpartum haemorrhage but has adverse effects including nausea, vomiting, hypertension and coronary artery spasm. Carbetocin is a newly developed long-acting oxytocin analogue that might be used as an uterotonic agent. We compare the efficacy and safety of intramuscular (IM) carbetocin with IM syntometrine in preventing primary postpartum haemorrhage. DESIGN: Prospective, double-blinded, randomised controlled trial. SETTING: Delivery suite of a university-based obstetrics unit. POPULATION: Women with singleton pregnancy achieving vaginal delivery after and throughout 34 weeks. METHODS: Three hundred and twenty-nine eligible women were randomised to receive either a single dose of 100 microgram IM carbetocin or 1 ml IM syntometrine (a mixture of 5 iu oxytocin and 0.5 mg ergometrine) at the end of second stage of labour. MAIN OUTCOME MEASURES: Difference in haemoglobin drop measured 2 days after delivery between the two groups. RESULTS: There was no difference in the drop of haemoglobin concentration within the first 48 hours between the two groups. The incidence of additional oxytocic injections, postpartum haemorrhage (blood loss > or = 500 ml) and retained placenta were also similar. The use of carbetocin was associated with significant lower incidence of nausea (relative risk [RR] 0.18, 95% confidence interval [CI] 0.04-0.78), vomiting (RR 0.1, 95% CI 0.01-0.74), hypertension 30 minutes (0 versus 8 cases, P < 0.01) and 60 minutes (0 versus 6 cases, P < 0.05) after delivery but a higher incidence of maternal tachycardia (RR 1.68, 95% CI 1.03-3.57). CONCLUSIONS: IM carbetocin is as effective as IM syntometrine in preventing primary postpartum haemorrhage after vaginal delivery. It is less likely to induce hypertension and has a low incidence of adverse effect. It should be considered as a good alternative to conventional uterotonic agents used in managing the third stage of labour.     

分娩过程中使用缩宫素对产后出血的影响

目前,产后出血仍是孕产妇死亡的主要原因之一,研究证实分娩过程中使用缩宫素增加了产后出血的发生风险,尤其是在缩宫素使用时间过长、浓度过高或未积极管理第三产程时。缩宫素受体的脱敏反应是其主要病理生理学机制,临床上表现为后续缩宫素诱导的子宫收缩反应性降低,进而引起宫缩乏力和产后出血。综述使用缩宫素与产后出血的相关性研究进展,帮助临床医生建立合理的缩宫素管理方案,减少宫缩乏力性产后出血的发生。     

Choice of oxytocic preparation for routine use in the management of the third stage of labour: an overview of the evidence from controlled trials

Prophylactic use of oxytocics reduces the risk of postpartum haemorrhage by about 40%. The analysis presented in this paper assesses which oxytocic preparation is associated with the least risk of postpartum haemorrhage and examines the relative effects of different preparations on the length of the third stage, the risk of manual removal of the placenta, blood pressure and other side-effects. A mixture of oxytocin and ergometrine (Syntometrine) appears to be the safest and most effective prophylactic of the alternatives which have been compared, but the quality of the evidence is not satisfactory. There is scope for a randomized comparison of Syntometrine with oxytocin to obtain unbiased and more precise estimates of their relative effects on postpartum haemorrhage, blood pressure and unpleasant side-effects.     

A Study to Compare the Efficacy of Misoprostol, Oxytocin, Methyl-ergometrine and Ergometrine–Oxytocin in Reducing Blood Loss in Active Management of 3rd Stage of Labor

Objectives

The purpose of the study was to compare the efficacy of misoprostol 400 μg per rectally, injection oxytocin 10 IU intramuscular, injection methylergometrine 0.2 mg intravenously and injection (0.5 mg ergometrine + 5 IU oxytocin) intramuscular on reducing blood loss in third stage of labor, duration of third stage of labor, effect on haemoglobin of the patient, need of additional oxytocics or blood transfusion and associated side effects and complications.

Study Design

A prospective non-randomized uncontrolled study was carried out in the Department of Obstetrics and Gynecology, SSG Hospital and Medical College, Baroda enrolling 200 women and dividing them into four groups. Active management of 3rd stage of labor was done using one of the 4 uterotonics as per the group of the patient. The main outcome measures were the amount of blood loss, the incidence of postpartum hemorrhage and a drop in hemoglobin concentration from before delivery to 24 h after delivery.

Results

Methylergometrine was found to be superior to rest of the drugs in the study with lowest duration of third stage of labor (P = 0.000096), lowest amount of blood loss (P = 0.000017) and lowest incidence of PPH (P = 0.03). There was no significant difference in the pre-delivery and the post-delivery hemoglobin concentration amongst the four groups with P = 0.061. The need of additional oxytocics and blood transfusion was highest with misoprostol as compared to all other drugs used in the study with P = 0.037 and 0.009, respectively. As regards side effects, misoprostol was associated with shivering and pyrexia in significantly high number of patients as compared to the other drugs used in the study while nausea, vomiting and headache were more associated with methylergometrine and ergometrine–oxytocin. However all the side effects were acceptable and preferable to the excessive blood loss.

Conclusion

Methylergometrine has the best uterotonic drug profile amongst the drugs used, strongly favouring its routine use as oxytocic for active management of third stage of labor. Misoprostol was found to cause a higher blood loss compared to other drugs and hence should be used only in low resource setting where other drugs are not available. The role of misoprostol in third stage of labor needs larger studies to be proved.     

Choice of oxytocic preparation for routine use in the management of the third stage of labour: an overview of the evidence from controlled trials

Summary. Prophylactic use of oxytocics reduces the risk of postpartum haemorrhage by about 40%. The analysis presented in this paper assesses which oxytocic preparation is associated with the least risk of postpartum haemorrhage and examines the relative effects of different preparations on the length of the third stage, the risk of manual removal of the placenta, blood pressure and other side-effects. A mixture of oxytocin and ergometrine (Syntometrine) appears to be the safest and most effective prophylactic of the alternatives which have been compared, but the quality of the evidence is not satisfactory. There is scope for a randomized comparison of Syntometrine with oxytocin to obtain unbiased and more precise estimates of their relative effects on postpartum haemorrhage, blood pressure and unpleasant side-effects.     

Effect of oxytocics on the blood pressure of normotensive Nigerian parturients

Background. The single most common direct obstetric disorder accounting for 25% of all maternal deaths globally is severe hemorrhage, generally occurring postpartum. Nearly all these deaths occur in the developing world. The role of oxytocic drugs in the management of the third stage of labor as a strategy to reduce maternal mortality has been emphasized. However, the adverse effects of these oxytocic agents, in particular ergometrine, have not been properly evaluated in our environment.

Objectives. To evaluate the effect of ergometrine and oxytocin on the cardiovascular system when used for active management of the third stage of labor.

Study design. A double-blind, randomized controlled study was carried out at the Federal Medical Centre, Makurdi over 24 months. Five hundred and ten patients were randomized to treatment with either 0.5 mg of intramuscular ergometrine or 10 IU of intravenous oxytocin, respectively, as single injections. Their effects on the cardiovascular system were observed using blood pressure as a marker.

Results. Ergometrine unlike oxytocin was observed to cause a significant rise in blood pressure, and this effect was most marked in the first 24 hours of the puerperium.

Conclusions. These results suggest that ergometrine may be safe in normotensive parturients but hazardous in hypertensive parturients in whom oxytocin would be a safer option.     

Ergometrine given during caesarean section and incidence of delayed postpartum haemorrhage due to uterine atony.

Delayed postpartum haemorrhage due to uterine atony after caesarean section was occurring in women in our recovery area despite many of them already having an oxytocin infusion running to prevent such a problem. We therefore decided to compare the incidence of such problems for a 2-month period before and after altering our uterotonic policy: in addition to the routine bolus dose of 5 units of oxytocin after delivery of the baby, we added 500 microg of intramuscular ergometrine during abdominal closure. We noticed a reduced number of massive postpartum haemorrhages due to an atonic uterus in the recovery room but an increased incidence of nausea and vomiting. No prophylactic anti-emetic was given during this pilot study. This small study suggests that 50 women would need to be given ergometrine at caesarean section to prevent one delayed massive haemorrhage from uterine atony and four extra women would suffer with vomiting. We feel this is reasonable and now use a prophylactic anti-emetic as well as delaying the ergometrine until closure of the rectus sheath which reduces the incidence of nausea and vomiting.     

The use of rectal misoprostol as active pharmacological management of the third stage of labor.

OBJECTIVE: To compare the effectiveness of rectal Misoprostol versus combined intramuscular oxytocin and ergometrine (O-E) in the management of the third stage of labor. METHODS: Low-risk women in 3rd stage of labor were allocated to receive either rectal Misoprostol [200micrograms (n = 25), 400 micrograms (n = 45)] or 5-units oxytocin and 0.2 mg ergometrine intramuscularly (n = 75). Clinical and hematological parameters were compared using t and chi-square tests. RESULTS: Both groups were well matched and had similar duration of the 3rd-stage of labor. Misoprostol users had lower 3rd-stage estimated blood loss and needed less further ecbolics compared to O-E group. Postpartum Hb and Hct levels were significantly lower in O-E group than Misoprostol group. Postpartum hypertension occurred more in O-E group. Subjects in Misoprostol group had more shivering. Subjects receiving 200 micrograms and 400 microgram Misoprostol had similar outcome variables. CONCLUSION: Rectal Misoprostol may be used safely in the management of the third stage of labor.     

Buccal misoprostol to decrease blood loss after vaginal delivery: a randomized trial

OBJECTIVE: To assess the efficacy of buccal misoprostol to decrease bleeding after vaginal delivery. METHODS: This was a randomized study of patients between 22 weeks and 42 weeks of gestation with anticipated vaginal delivery. Patients were given either a 200-mug misoprostol tablet or placebo in the buccal space at the time of cord clamping. A continuous dilute intravenous oxytocin infusion was given to all patients at delivery of the placenta. Postpartum hemorrhage was defined as blood loss exceeding 500 mL. Sample size calculations based on previous studies assumed a 13% incidence of postpartum hemorrhage in the control group. To show a statistically significant reduction of postpartum hemorrhage a total of 1,604 patients would be required in each group. RESULTS: A total of 848 patients were enrolled and 756 randomly assigned, 377 in the misoprostol group and 379 in the placebo group. Demographic, antepartum, and intrapartum characteristics were similar between the groups. The incidence of postpartum hemorrhage, 3% compared with 5%, (relative risk 0.65, 95% confidence interval 0.33-1.29, P = .22), mean estimated blood loss, 322 compared with 329 mL, (P = .45), and mean minutes of the third stage of labor, 6.7 compared with 6.9 (P = .52) were similar between the groups, misoprostol and placebo, respectively. Hemoglobin difference before and after delivery, need for second or third uterotonic agent, and all measured neonatal variables including birth weights, and umbilical cord pH were similar between the groups. CONCLUSION: Buccal misoprostol at cord clamping is no more effective than placebo in reducing postpartum hemorrhage.     

A comparison of prophylactic intramuscular ergometrine and oxytocin for women in the third stage of labor

Objective

To compare the efficacy and adverse effects of ergometrine and oxytocin given intramuscularly for the prevention of postpartum hemorrhage during the third stage of labor.

Methods

The study included women with a singleton pregnancy of at least 28 weeks’ gestation who had a vaginal delivery. High-risk pregnancies were excluded. Oxytocin (10 IU) or ergometrine (0.5 mg) were administered intramuscularly in a blinded pattern immediately after delivery of the infant. An intention-to-treat analysis was performed.

Results

Postpartum blood loss (301.8 ± 109.2 mL versus 287.1 ± 84.4 mL, P = 0.011) and packed cell volume (30.7 ± 1.7% versus 31.6 ± 2.0%; Z = 0.00; P = 0.008) were considerably reduced among parturients who received intramuscular ergometrine. The rates of therapeutic oxytocics use, blood transfusion, placental retention, and manual removal of the placenta were significantly higher in the oxytocin group. No significant differences between the groups were observed in terms of adverse effects, with the exception of diastolic hypertension, which was more common in the ergometrine group (odds ratio, 0.00; 95% confidence interval, 0.00–0.75; P = 0.007).

Conclusion

Intramuscular ergometrine is superior to intramuscular oxytocin in averting postpartum hemorrhage during the third stage of labor. There are no significant risks of adverse effects except for diastolic hypertension.Pan African Clinical Trial Registry (www.pactr.org): 201105000292708.     

Prevention of postpartum hemorrhage by uterotonic agents: comparison of oxytocin and methylergometrine in the management of the third stage of labor

OBJECTIVES: To determine the efficacy of intravenous oxytocin administration compared with intravenous methylergometrine administration for the prevention of postpartum hemorrhage (PPH), and the significance of administration at the end of the second stage of labor compared with that after the third stage. METHODS: A prospective study was undertaken: two major groups (oxytocin group and methylergometrine group) of 438 women with singleton pregnancy and vaginal delivery were studied during a 15-month period. These two groups were subdivided into three subgroups: 1. intravenous injection (two minutes) group immediately after the delivery of the fetal anterior shoulder, 2. intravenous injection (two minutes) group immediately after the delivery of the placenta, and 3. drip infusion (20 min) group immediately after the delivery of the fetal head. In each group, quantitative postpartum blood loss, frequencies of blood loss >500 ml, and need of additional uterotonic treatment were evaluated. RESULTS: As compared with methylergometrine, oxytocin administration was associated with a significant reduction in postpartum blood loss and in frequency of blood loss >500 ml. The risk of PPH was significantly reduced with intravenous injection of oxytocin after delivery of the fetal anterior shoulder, compared with intravenous injection of oxytocin after expulsion of the placenta (OR 0.33, 95%CI 0.11-0.98) and intravenous injection of methylergometrine after delivery of the fetal anterior shoulder (OR 0.31, 95%CI 0.11-0.85). CONCLUSIONS: Intravenous injection of 5 IU oxytocin immediately after delivery of fetal anterior shoulder is the treatment of choice for prevention of PPH in patients with natural course of labor.     

Misoprostol and active management of the third stage of labor.

OBJECTIVE: To compare current practices for the active management of the third stage of labor (AMTSL) with the use of 600 mug of oral misoprostol. METHODS: An operations research study was designed to compare blood loss with current AMTSL practices and misoprostol use. RESULTS: Women in the misoprostol group were less likely to bleed 500 ml or more (adjusted odds ratio, 0.30; 95% confidence interval, 0.16-0.56) compared with those in the current practices group. In the current practices group 73% women required interventions because of postpartum hemorrhage, compared with 11% in the misoprostol group. CONCLUSION: In situations where oxytocin and or ergometrine are not consistently and appropriately used during third stage of labor, misoprostol should be considered for inclusion in the AMTSL protocol.     

The length of the third stage of labor and the risk of postpartum hemorrhage

OBJECTIVE: To estimate whether the length of the third stage of labor is correlated with postpartum hemorrhage. METHODS: In this prospective observational study women delivering vaginally in a tertiary obstetric hospital were assessed for postpartum hemorrhage. All women were actively managed with the administration of oxytocin upon delivery of the anterior shoulder. Blood loss was measured at each delivery in collecting devices, and drapes and sheets were weighed to calculate the blood loss at each vaginal delivery. Postpartum hemorrhage was defined as more than 1,000 mL blood loss or hemodynamic instability related to blood loss requiring a blood transfusion. RESULTS: During a 24-month period there were 6,588 vaginal deliveries in a single tertiary obstetric hospital, and postpartum hemorrhage occurred in 335 of these (5.1%). The median length of the third stage of labor was similar in women having and those not having a postpartum hemorrhage. The risk of postpartum hemorrhage was significant at 10 minutes, odds ratio (OR) 2.1, 95% confidence interval (CI), 1.6-2.6; at 20 minutes, OR 4.3, 95% CI 3.3-5.5; and at 30 minutes OR 6.2, 95% CI 4.6-8.2. The best predictor for postpartum hemorrhage using receiver operating characteristic curves was 18 minutes. CONCLUSION: A third stage of labor longer than 18 minutes is associated with a significant risk of postpartum hemorrhage. After 30 minutes the odds of having postpartum hemorrhage are 6 times higher than before 30 minutes. LEVEL OF EVIDENCE: III.