Oxytocin exposure during labor among women with postpartum hemorrhage secondary to uterine atony

Continuation versus discontinuation of intravenous oxytocin in the active phase of labour

OBJECTIVES

This is a protocol for a Cochrane Review (intervention). The objectives are as follows: To assess the effects of discontinuing intravenous oxytocin stimulation in pregnant women during the active phase of induced or augmented labour.

Oxytocin with calcium vs oxytocin for induction of labor in women with term premature rupture of membranes: a randomized controlled trial

BACKGROUND

Intravenous calcium administration has shown promise in enhancing uterine contractions and reducing blood loss during cesarean delivery, but this regimen has not been compared in vaginal labor induction.

OBJECTIVE

This study aimed to determine the efficacy of oxytocin combined with calcium vs oxytocin alone for inducing labor in women with term premature rupture of membranes.

STUDY DESIGN

This single-blind, randomized controlled trial was conducted between October 2022 and May 2023 at a tertiary university hospital. Patients diagnosed with premature rupture of membranes were randomly allocated into 2 groups. The intervention group received a bolus of 10 mL of calcium gluconate followed by a continuous infusion of oxytocin via a pump (n=210), whereas the control group received only oxytocin infusion (n=218). The primary outcome was successful vaginal deliveries within 24 hours after labor induction. The secondary outcomes included the interval from labor induction to delivery, vaginal delivery blood loss, and maternal and neonatal complications.

RESULTS

Baseline characteristics, including maternal age, body mass index, and Bishop score before labor induction, were comparable between the groups. The rate of vaginal delivery within 24 hours after labor induction was statistically higher in the intervention group (79.52% vs 70.64%; P=.04). The participants in the intervention group experienced a shortened interval between labor induction and delivery (10.48 vs 11.25 hours; P=.037) and demonstrated a higher success rate in labor induction assessed by the onset of the active phase (93.80% vs 87.61%; P=.04) without increasing the cesarean delivery rate. Reduced hemorrhage was observed in the intervention group (242.5 vs 255.0 mL; P=.0015), and the maternal and neonatal outcomes were comparable between the groups.

CONCLUSION

The coadministration of calcium and oxytocin in labor induction among pregnancies with premature rupture of membranes was more efficient and safer than the administration of oxytocin alone. Our research suggests that the combination therapy of calcium and oxytocin may offer significant advantages during the process of labor induction and result in better outcomes. VIDEO ABSTRACT.

Variations in the use of oxytocin for augmentation of labour in Sweden: a population-based cohort study

National Swedish data shows substantial variation in the use of oxytocin for augmentation of spontaneous labour between obstetric units. This study aimed to investigate if variations in the use of oxytocin augmentation are associated with maternal and infant characteristics or clinical factors. We used a cohort design including women allocated to Robson group 1 (nulliparous women, gestational week ≥ 37 + 0, with singleton births in cephalic presentation and spontaneous onset of labour) and 3 (parous women, gestational week ≥ 37 + 0, with singleton births in cephalic presentation, spontaneous onset of labour, and no previous caesarean birth). Crude and adjusted logistic regression models with marginal standardisation were used to estimate risk ratios (RR) and risk differences (RD) with 95% confidence intervals (CI) for oxytocin use by obstetric unit. An interaction analysis was performed to investigate the potential modifying effect of epidural. The use of oxytocin varied between 47 and 73% in Robson group 1, and 10% and 33% in Robson group 3. Compared to the remainder of Sweden, the risk of oxytocin augmentation ranged from 13% lower (RD - 13.0, 95% CI - 15.5 to - 10.6) to 14% higher (RD 14.0, 95% CI 12.3-15.8) in Robson group 1, and from 6% lower (RD - 5.6, 95% CI - 6.8 to - 4.5) to 18% higher (RD 17.9, 95% CI 16.5-19.4) in Robson group 3. The most notable differences in risk estimates were observed among women in Robson group 3 with epidural. In conclusion, variations in oxytocin use remained despite adjusting for risk factors. This indicates unjustified differences in use of oxytocin in clinical practice.

Cumulative oxytocin dose in spontaneous labour - Adverse postpartum outcomes, childbirth experience, and breastfeeding

OBJECTIVES

This study aimed to determine the association between the total cumulative oxytocin dose during labour and adverse postpartum outcomes, childbirth experience and breastfeeding in term primiparous women with spontaneous onset of labour.

STUDY DESIGN

A prospective observational multicentre study, including 1395 women with spontaneous labour, in seven hospitals in Southeast Sweden. Multivariable logistic regression (Crude Odds Ratios (OR) and adjusted OR (aOR) for relevant confounders) was used to analyze the association between oxytocin dose and postpartum outcomes. The exposure was the cumulative oxytocin dose during labour, classified in percentiles (<25th, 25-75th, >75th). The outcomes were occurrence of obstetric anal sphincter injury, postpartum haemorrhage (blood loss > 1000 ml), Apgar score < 7 at five minutes, umbilical cord arterial pH, postpartum bladder overdistension, exclusive breastfeeding at one week and three months, and the woman's perceived birth experience.

RESULTS

Women receiving high amounts (>75th percentile, >4370 mU) of oxytocin infusion during labour had an increased risk of postpartum haemorrhage (OR 2.73 (1.78-4.19)), an overdistended bladder (OR 2.19 (1.11-4.31)), an infant with an Apgar score < 7 at five minutes (OR 2.89 (1.27-6.57)), a negative birth experience (OR 1.83 (1.25-2.69)), and a decreased chance of exclusive breastfeeding at one week (OR 0.63 (0.41-0.96)). After adjusting for confounders, all outcomes remained statistically significant except risk of low Apgar score and chance of exclusive breastfeeding.

CONCLUSION

In women with high cumulative oxytocin dose during labour prompt, and prophylactic administration of uterotonics after delivery of the placenta should be considered to reduce the risk of postpartum haemorrhage. The risk for bladder overdistension can be reduced by implementing routines for observation for signs of bladder filling in the early postpartum period, as well as routine use of bladder scans post micturition to assess for successful bladder emptying. As women's birth experience have a major impact on their future mental health, should be routinely assessed postpartum, and support should be offered to women with negative experiences.

The physiology and pharmacology of oxytocin in labor and in the peripartum period

Oxytocin is a reproductive hormone implicated in the process of parturition and widely used during labor. Oxytocin is produced within the supraoptic nucleus and paraventricular nucleus of the hypothalamus and released from the posterior pituitary lobe into the circulation. Oxytocin is released in pulses with increasing frequency and amplitude in the first and second stages of labor, with a few pulses released in the third stage of labor. During labor, the fetus exerts pressure on the cervix of the uterus, which activates a feedforward reflex-the Ferguson reflex-which releases oxytocin. When myometrial contractions activate sympathetic nerves, it decreases oxytocin release. When oxytocin binds to specific myometrial oxytocin receptors, it induces myometrial contractions. High levels of circulating estrogen at term make the receptors more sensitive. In addition, oxytocin stimulates prostaglandin synthesis and release in the decidua and chorioamniotic membranes by activating a specific type of oxytocin receptor. Prostaglandins contribute to cervical ripening and uterine contractility in labor. The oxytocin system in the brain has been implicated in decreasing maternal levels of fear, pain, and stress, and oxytocin release and function during labor are stimulated by a social support. Moreover, studies suggest, but have not yet proven, that labor may be associated with long-term, behavioral and physiological adaptations in the mother and infant, possibly involving epigenetic modulation of oxytocin production and release and the oxytocin receptor. In addition, infusions of synthetic oxytocin are used to induce and augment labor. Oxytocin may be administered according to different dose regimens at increasing rates from 1 to 3 mIU/min to a maximal rate of 36 mIU/min at 15- to 40-minute intervals. The total amount of synthetic oxytocin given during labor can be 5 to 10 IU, but lower and higher amounts of oxytocin may also be given. High-dose infusions of oxytocin may shorten the duration of labor by up to 2 hours compared with no infusion of oxytocin; however, it does not lower the frequency of cesarean delivery. When synthetic oxytocin is administered, the plasma concentration of oxytocin increases in a dose-dependent way: at infusion rates of 20 to 30 mIU/min, plasma oxytocin concentration increases approximately 2- to 3-fold above the basal level. Synthetic oxytocin administered at recommended dose levels is not likely to cross the placenta or maternal blood-brain barrier. Synthetic oxytocin should be administered with caution as high levels may induce tachystole and uterine overstimulation, with potentially negative consequences for the fetus and possibly the mother. Of note, 5 to 10 IU of synthetic oxytocin is often routinely given as an intravenous or intramuscular bolus administration after delivery to induce uterine contractility, which, in turn, induces uterine separation of the placenta and prevents postpartum hemorrhage. Furthermore, it promotes the expulsion of the placenta.

Trends in postpartum hemorrhage and manual removal of the placenta and the association with childbirth interventions: A Dutch nationwide cohort study

BACKGROUND

Because the cause of increasing rates of postpartum hemorrhage (PPH) and manual placental removal (MROP) is still unknown, we described trends in PPH, MROP, and childbirth interventions and examined factors associated with changes in rates of PPH and MROP.

METHODS

This nationwide cohort study used national perinatal registry data from 2000 to 2014 (n = 2,332,005). We included births of women who gave birth to a term singleton child in obstetrician-led care or midwife-led care. Multivariable logistic regression analyses were used to examine associations between characteristics and interventions, and PPH ≥ 1000 mL and MROP.

RESULTS

PPH rates increased from 4.3% to 6.6% in obstetrician-led care and from 2.5% to 4.8% in midwife-led care. MROP rates increased from 2.4% to 3.4% and from 1.0% to 1.4%, respectively. A rising trend was found for rates of induction and augmentation of labor, pain medication, and cesarean section, while rates of episiotomy and assisted vaginal birth declined. Adjustments for characteristics and childbirth interventions did not result in large changes in the trends of PPH and MROP. After adjustments for childbirth interventions, in obstetrician-led care, the odds ratio (OR) of PPH in 2014 compared with the reference year 2000 changed from 1.66 (95% CI 1.57-1.76) to 1.64 (1.55-1.73) among nulliparous women and from 1.56 (1.47-1.66) to 1.52 (1.44-1.62) among multiparous women. For MROP, the ORs changed from 1.51 (1.38-1.64) to 1.36 (1.25-1.49) and from 1.56 (1.42-1.71) to 1.45 (1.33-1.59), respectively.

CONCLUSIONS

Rising PPH trends were not associated with changes in population characteristics and rising childbirth intervention rates. The rising MROP was to some extent associated with rising intervention rates.

Oxytocin: physiology, pharmacology, and clinical application for labor management

Oxytocin is a peptide hormone that plays a key role in regulating the female reproductive system, including during labor and lactation. It is produced primarily in the hypothalamus and secreted by the posterior pituitary gland. Oxytocin can also be administered as a medication to initiate or augment uterine contractions. To study the effectiveness and safety of oxytocin, previous studies have randomized patients to low- and high-dose oxytocin infusion protocols either alone or as part of an active management of labor strategy along with other interventions. These randomized trials demonstrated that active management of labor and high-dose oxytocin regimens can shorten the length of labor and reduce the incidence of clinical chorioamnionitis. The safety of high-dose oxytocin regimens is also supported by no associated differences in fetal heart rate abnormalities, postpartum hemorrhage, low Apgar scores, neonatal intensive care unit admissions, and umbilical artery acidemia. Most studies reported no differences in the cesarean delivery rates with active management of labor or high-dose oxytocin regimens, thereby further validating its safety. Oxytocin does not have a predictable dose response, thus the pharmacologic effects and the amplitude and frequency of uterine contractions are used as physiological parameters for oxytocin infusion titration to achieve adequate contractions at appropriate intervals. Used in error, oxytocin can cause patient harm, highlighting the importance of precise administration using infusion pumps, institutional safety checklists, and trained nursing staff to closely monitor uterine activity and fetal heart rate changes. In this review, we summarize the physiology, pharmacology, infusion regimens, and associated risks of oxytocin.

Induction of labor and risk of postpartum hemorrhage in women with vaginal delivery: A propensity score analysis

OBJECTIVE

To explore the association between induction of labor (IOL) and postpartum hemorrhage (PPH) after vaginal delivery.

METHODS

We included women from the merged database of three randomized prospective trials (TRACOR, CYTOCINON, and TRAAP) that measured postpartum blood loss precisely, with standardized methods. IOL was considered overall and according to its method. The association between IOL and PPH was tested by multivariate logistic regression modeling, adjusted for confounders, and by propensity score matching. The role of potential intermediate factors, i.e. estimated quantity of oxytocin administered during labor and operative vaginal delivery, was assessed with structural equation modeling.

RESULTS

Labor was induced for 1809 of the 9209 (19.6%) women. IOL was associated with a significantly higher risk of PPH of 500 mL or more (adjusted odds ratio 1.56, 95% confidence interval 1.42-1.70) and PPH of 1000 mL or more (adjusted odds ratio 1.51, 95% confidence interval 1.16-1.96). The risk of PPH increased similarly regardless of the method of induction. The results were similar after propensity score matching (odds ratio for PPH ≥500 mL 1.57, 95% confidence interval 1.33-1.87, odds ratio for PPH ≥1000 mL 1.57, 95% confidence interval 1.06-2.07). Structural equation modeling showed that 34% of this association was mediated by the quantity of oxytocin administered during labor and 1.3% by women who underwent operative vaginal delivery.

CONCLUSION

Among women with vaginal delivery, the risk of PPH is higher in those with IOL, regardless of its method, and after accounting for indication bias. The quantity of oxytocin administered during labor may explain one third of this association.

Association between duration of intrapartum oxytocin exposure and obstetric hemorrhage

PURPOSE

Prolonged duration of intrapartum oxytocin exposure is included as a risk factor within widely adopted obstetric hemorrhage risk stratification tools. However, the duration of exposure that confers increased risk is poorly understood. This study aimed to assess the association between duration of intrapartum oxytocin exposure and obstetric blood loss, as measured by quantitative blood loss, and hemorrhage-related maternal morbidity.

METHODS

This was a retrospective cohort study of all deliveries from 2018 to 2019 at a single medical center. We included patients who had received any intrapartum oxytocin, and we categorized them into 1 of 5 groups: > 0-2, ≥ 2-4, ≥ 4-6, ≥ 6-12, and ≥ 12 h of intrapartum oxytocin exposure. The primary outcomes were mean quantitative blood loss, proportion with obstetric hemorrhage (defined as quantitative blood loss ≥ 1000 mL), and proportion with obstetric hemorrhage-related morbidity, a composite of hemorrhage-related morbidity outcomes. Secondary outcomes were hemorrhage-related pharmacologic and procedural interventions. A stratified analysis was also conducted to examine primary and secondary outcomes by delivery mode.

RESULTS

Of 5332 deliveries between January 1, 2018 and December 31, 2019 at our institution, 2232 (41.9%) utilized oxytocin for induction or augmentation. 326 (14.6%) had exposure of > 0-2 h, 295 (13.2%) ≥ 2-4 h, 298 (13.4%) ≥ 4-6 h, 562 (25.2%) ≥ 6-12 h, and 751 (33.6%) ≥ 12 h. Across all deliveries, there was higher mean quantitative blood loss (p < 0.01) as well as increased odds of obstetric hemorrhage (adjusted odds ratio [aOR] 1.52, 95% confidence interval [CI] 1.21-1.91) for those with ≥ 12 h of oxytocin compared to all groups between > 0-12 h of exposure. In our stratified analysis, ≥ 12 h of oxytocin exposure was associated with higher mean quantitative blood loss (p = 0.04) and odds of obstetric hemorrhage in vaginal deliveries (aOR 1.47, 95% CI: 1.03-2.11), though not in cesarean deliveries (aOR 1.16, 95% CI 0.82-1.62). There were no differences in proportion with obstetric hemorrhage-related morbidity across all deliveries (p = 0.40) or in the stratified analysis.

CONCLUSION

Intrapartum oxytocin exposure of ≥ 12 h was associated with increased quantitative blood loss and odds of obstetric hemorrhage in vaginal, but not cesarean, deliveries.

Oxytocin is not associated with postpartum hemorrhage in labor augmentation in a retrospective cohort study in the United States

BACKGROUND

Previous studies reported conflicting results on the relationship between oxytocin use for labor augmentation and the risk of postpartum hemorrhage, probably because it is rather challenging to disentangle oxytocin use from labor dystocia.

OBJECTIVE

This study aimed to investigate the independent association between oxytocin use for augmentation and the risk of postpartum hemorrhage by using advanced statistical modeling to control for labor patterns and other covariates.

STUDY DESIGN

We used data from 20,899 term, cephalic, singleton pregnancies of patients with spontaneous onset of labor and no previous cesarean delivery from Intermountain Healthcare in Utah in the Consortium on Safe Labor. Presence of postpartum hemorrhage was identified on the basis of a clinical diagnosis. Propensity scores were calculated using a generalized linear mixed model for oxytocin use for augmentation, and covariate balancing generalized propensity score was applied to obtain propensity scores for the duration and total dosage of oxytocin augmentation. A weighted generalized additive mixed model was used to depict dose-response curves between the duration and total dosage of oxytocin augmentation and the outcomes. The average treatment effects of oxytocin use for augmentation on postpartum hemorrhage and estimated blood loss (mL) were assessed by inverse probability weighting of propensity scores.

RESULTS

The odds of both postpartum hemorrhage and estimated blood loss increased modestly when the duration and/or total dosage of oxytocin used for augmentation increased. However, in comparison with women for whom oxytocin was not used, oxytocin augmentation was not clinically or statistically significantly associated with estimated blood loss (6.5 mL; 95% confidence interval, 2.5-10.3) or postpartum hemorrhage (adjusted odds ratio, 1.02; 95% confidence interval, 0.82-1.24) when rigorously controlling for labor pattern and potential confounders. The results remained consistent regardless of inclusion of women with an intrapartum cesarean delivery.

CONCLUSION

The odds of postpartum hemorrhage and estimated blood loss increased modestly with increasing duration and total dosage of oxytocin augmentation. However, in comparison with women for whom oxytocin was not used and after controlling for potential confounders, there was no clinically significant association between oxytocin use for augmentation and estimated blood loss or the risk of postpartum hemorrhage.

Predicting risk of postpartum hemorrhage associated with vaginal delivery of twins: A retrospective study

Many studies have only focused on the risk factors for postpartum hemorrhage (PPH) in singleton vaginal deliveries and twin cesarean deliveries. We analyzed the factors of influencing PPH occurrence in twin vaginal deliveries and developed a nomogram for clinical application. This retrospective study included 274 pregnant women with twin pregnancies who were hospitalized for delivery from January 2014 to December 2018. The patients opted for vaginal delivery and experienced spontaneous labor. Univariate analysis of PPH risk factors was performed. Multivariate analysis was performed using the least absolute shrinkage and selection operator (LASSO) to obtain relevant factors and build a prediction model, which was presented as a nomogram. The model was internally validated by bootstrap self-sampling method. Model accuracy was evaluated with the concordance index (C-index). There were 36 (13.14%) and 238 (86.9%) patients in the PPH and no PPH groups, respectively. Univariate analysis identified twin chorionicity, hypertensive disorders complicating pregnancy (HDCP), anemia in pregnancy, delivery mode of the second twin, oxytocin use during labor, postpartum curettage, cervical laceration, intrapartum fever, fibrinogen degradation products (FDP), and platelet count (PLT) as significant PPH factors. On multivariate analysis, HDCP, anemia in pregnancy, intrapartum fever, oxytocin use during labor, fetal distress, PLT, direct bilirubin, and FDP were noted as significant PPH factors and were included in the prediction model. A C-index of 0.816 was noted after internal validation, and the calibration curve showed good consistency. We developed a model to predict PPH risk in the vaginal delivery of twin pregnancies and visualized it with a nomogram that can be applied clinically to assess PPH risk and aid PPH prevention.

A prolonged latent phase: An early career in oxytocin during birth

•The author, a nurse-midwife scientist, shares her path to the study of the causes and consequences of clinical oxytocin use.•This paper highlights mentors and key research that informed new thinking about the role of oxytocin during parturition.•Future directions for improving maternal care during childbirth are presented, including genetic and epigenetic perspectives.

Association of oxytocin augmentation and duration of labour with postpartum haemorrhage: A cohort study of nulliparous women

OBJECTIVE

Both duration of labour and use of oxytocin for augmentation are known risk factors for postpartum haemorrhage but distinguishing between the significance of these factors is complex. In this study, we aimed to investigate the association between both labour duration and oxytocin augmentation, for postpartum haemorrhage.

DESIGN

A cohort study based on a secondary analysis of a cluster-randomised trial.

PARTICIPANTS AND SETTING

Term nulliparous women with a single foetus in cephalic presentation, spontaneous onset of active labour and a vaginal birth. The participants were originally included in cluster-randomised trial conducted in Norway from December 1, 2014, to January 31, 2017, that aimed to compare the frequency of intrapartum caesarean sections when adhering to the WHO partograph versus Zhang's guideline.

MEASUREMENTS

The data were analysed through four statistical models. Model 1 investigated the effect of oxytocin augmentation as a dichotomous variable (yes/no); Model 2 investigated the effect of the duration of oxytocin augmentation; Model 3 investigated the effect of the maximum dose of oxytocin; and Model 4 investigated the effect of both the duration of augmentation and the maximum dose of oxytocin. All four models included duration of labour divided into five time-intervals. We used binary logistic regression to estimate the odds ratios of postpartum haemorrhage, defined as blood loss of ≥ 1000 ml, including a random intercept for hospital and mutually adjusting for oxytocin augmentation and labour duration in addition to maternal age, maternal marital status, maternal higher education level, maternal smoking habits in the first trimester, maternal body mass index and birth weight.

FINDINGS

Model 1 found a significant association between the use of oxytocin and postpartum haemorrhage. In Model 2, oxytocin augmentation of ≥ 4.5 h was associated with postpartum haemorrhage. In Model 3, we found an association between a maximum dose of oxytocin of ≥ 20 mU/min and postpartum haemorrhage. Model 4 showed that a maximum dose of oxytocin ≥ 20 mU/min was associated with postpartum haemorrhage both for those augmented < 4.5 h and for those augmented ≥ 4.5 h. Duration of labour was associated with postpartum haemorrhage in all models if lasting ≥ 16 h.

KEY CONCLUSIONS

We found both oxytocin augmentation and labour duration to be associated with postpartum haemorrhage. Oxytocin doses of ≥ 20 mU/min and a labour duration of ≥ 16 h showed an independent association.

IMPLICATION FOR PRACTICE

The potent drug oxytocin should be carefully administered, as doses of ≥ 20 mU/min were associated with an increased risk of PPH, regardless of the duration of oxytocin augmentation.

Effect of an oxytocin protocol on secondary uterotonic use in patients undergoing Cesarean delivery

PURPOSE

Protocol-driven oxytocin regimens can reduce oxytocin administration compared with a nonprotocol free-flow continuous infusion. Our aim was to compare secondary uterotonic use between a modified "rule of threes" oxytocin protocol and a free-flow continuous oxytocin infusion after Cesarean delivery.

METHODS

We conducted a retrospective before-and-after study to compare patients who underwent Cesarean delivery between 1 January 2010 and 31 December 2013 (preprotocol) with patients who underwent Cesarean delivery between 1 January 2015 and 31 August 2017 (postprotocol). The preprotocol group received free-flow oxytocin administration and the postprotocol group received oxytocin according to a modified rule of threes algorithm. The primary outcome was secondary uterotonic use and the secondary outcomes included blood transfusion, hemoglobin value < 8 g·dL-1, and estimated blood loss.

RESULTS

In total, 4,010 Cesarean deliveries were performed in 3,637 patients (2,262 preprotocol and 1,748 postprotocol). The odds of receiving secondary uterotonic drugs were increased in the postprotocol group (odds ratio [OR], 1.33; 95% confidence interval [CI], 1.04 to 1.70; P = 0.02). Patients in the postprotocol group were less likely to receive a blood transfusion. Nevertheless, the two groups were similar for the composite end point of transfusion or hemoglobin < 8 g·dL-1 (OR, 0.86; 95% CI, 0.66 to 1.11; P = 0.25). The odds of an estimated blood loss greater than 1,000 mL were reduced in the postprotocol group (OR, 0.64; 95% CI, 0.50 to 0.84; P = 0.001).

CONCLUSIONS

Patients in the modified rule of threes oxytocin protocol group were more likely to receive a secondary uterotonic than those in the preprotocol group. Estimated blood loss and transfusion outcomes were similar.

The In Vitro Contractile Response of Canine Pregnant Myometrium to Oxytocin and Denaverine Hydrochloride

In pregnant bitches, the response to oxytocin and denaverine hydrochloride in dystocia management is usually poor. To better understand the effect of both drugs on myometrial contractility, the circular and longitudinal muscle layers were examined in an organ bath. For each layer, three myometrial strips were stimulated twice, each with one of three oxytocin concentrations. The effect of denaverine hydrochloride was studied once in direct combination with oxytocin and alone with subsequent oxytocin administration. Contractions were recorded and evaluated for average amplitude, mean force, area under the curve (AUC), and frequency. Effects of different treatments were analyzed and compared within and between layers. In the circular layer, oxytocin significantly increased amplitude and mean force compared to untreated controls regardless of stimulation cycles or concentrations. In both layers, high oxytocin concentrations caused tonic contractions, while the lowest concentration created regular rhythmic contractions. Longitudinal layer tissue responded to oxytocin with a significantly decreased contractility when stimulated twice, presumably a sign of desensitization. Denaverine hydrochloride neither affected oxytocin induced contractions nor showed a priming effect to subsequent oxytocin. Thus, no benefit of denaverine hydrochloride on myometrial contractility was found in the organ bath. Our results suggest a better efficiency of low-dose oxytocin in canine dystocia management.

Maternal and newborn plasma oxytocin levels in response to maternal synthetic oxytocin administration during labour, birth and postpartum - a systematic review with implications for the function of the oxytocinergic system

BACKGROUND

The reproductive hormone oxytocin facilitates labour, birth and postpartum adaptations for women and newborns. Synthetic oxytocin is commonly given to induce or augment labour and to decrease postpartum bleeding.

AIM

To systematically review studies measuring plasma oxytocin levels in women and newborns following maternal administration of synthetic oxytocin during labour, birth and/or postpartum and to consider possible impacts on endogenous oxytocin and related systems.

METHODS

Systematic searches of PubMed, CINAHL, PsycInfo and Scopus databases followed PRISMA guidelines, including all peer-reviewed studies in languages understood by the authors. Thirty-five publications met inclusion criteria, including 1373 women and 148 newborns. Studies varied substantially in design and methodology, so classical meta-analysis was not possible. Therefore, results were categorized, analysed and summarised in text and tables.

RESULTS

Infusions of synthetic oxytocin increased maternal plasma oxytocin levels dose-dependently; doubling the infusion rate approximately doubled oxytocin levels. Infusions below 10 milliunits per minute (mU/min) did not raise maternal oxytocin above the range observed in physiological labour. At high intrapartum infusion rates (up to 32 mU/min) maternal plasma oxytocin reached 2-3 times physiological levels. Postpartum synthetic oxytocin regimens used comparatively higher doses with shorter duration compared to labour, giving greater but transient maternal oxytocin elevations. Total postpartum dose was comparable to total intrapartum dose following vaginal birth, but post-caesarean dosages were higher. Newborn oxytocin levels were higher in the umbilical artery vs. umbilical vein, and both were higher than maternal plasma levels, implying substantial fetal oxytocin production in labour. Newborn oxytocin levels were not further elevated following maternal intrapartum synthetic oxytocin, suggesting that synthetic oxytocin at clinical doses does not cross from mother to fetus.

CONCLUSIONS

Synthetic oxytocin infusion during labour increased maternal plasma oxytocin levels 2-3-fold at the highest doses and was not associated with neonatal plasma oxytocin elevations. Therefore, direct effects from synthetic oxytocin transfer to maternal brain or fetus are unlikely. However, infusions of synthetic oxytocin in labour change uterine contraction patterns. This may influence uterine blood flow and maternal autonomic nervous system activity, potentially harming the fetus and increasing maternal pain and stress.

Clinical Experiences and Mechanism of Action with the Use of Oxytocin Injection at Parturition in Domestic Animals: Effect on the Myometrium and Fetuses

Oxytocin is a key hormone for parturition and maternal traits in animals. During the peripartum period, the levels of endogenous oxytocin dictate physiological events such as myometrial contractions, prostaglandin production with the subsequent increase in oxytocin receptors, and the promotion of lactation when administered immediately after birth. While this hormone has some benefits regarding these aspects, the exogenous administration of oxytocin has been shown to have detrimental effects on the fetus, such as asphyxia, meconium staining, ruptured umbilical cords, and more dystocia cases in females. This review aims to analyze the main effects of oxytocin on myometrial activity during parturition, and its potential favorable and negative administration effects reflected in the fetus health of domestic animals. In conclusion, it is convenient to know oxytocin's different effects as well as the adequate doses and the proper moment to administrate it, as it can reduce labor duration, but it can also increase dystocia.

Protocol for postpartum haemorrhage including massive transfusion

Postpartum haemorrhage (PPH) is one of the most common causes of maternal mortality worldwide. Management of PPH depends on the severity of bleeding. If the bleeding is severe, aorta compression can reduce bleeding. It should be followed by insertion of two coarse needles for intravenous access and blood sampling for haemoglobin and haemostasis. Further on, monitoring of vital parameters, as well as provision of extra oxygen and warm crystalloids, should be performed. Uterine atony is the most common cause of PPH and local guidelines for uterotonic drug selection should be followed. Patients with ongoing bleeding should immediately receive surgical care for bleeding control. During severe ongoing bleeding, haemostasis care includes early tranexamic acid, transfusion in ratio 4:4:1 (blood:plasma:platelets), and extra fibrinogen intravenously. If not severe PPH, use goal-directed therapy. During general anaesthesia and uterine atony, stop volatile anaesthesia and change to intravenous anaesthesia.

Oxytocin receptor single nucleotide polymorphism predicts atony-related postpartum hemorrhage

BACKGROUND

Postpartum hemorrhage remains a key contributor to overall maternal morbidity in the United States. Current clinical assessment methods used to predict postpartum hemorrhage are unable to prospectively identify about 40% of hemorrhage cases. Oxytocin is a first-line pharmaceutical for preventing and treating postpartum hemorrhage, which acts through oxytocin receptors on uterine myocytes. Existing research indicates that oxytocin function is subject to variation, influenced in part by differences in the DNA sequence within the oxytocin receptor gene. One variant, rs53576, has been shown to be associated with variable responses to exogenous oxytocin when administered during psychological research studies. How this variant may influence myometrial oxytocin response in the setting of third stage labor has not been studied. We tested for differences in the frequency of the oxytocin receptor genotype at rs53576 in relationship to the severity of blood loss among a sample of individuals who experienced vaginal birth.

METHODS

A case-control prospective design was used to enroll 119 postpartum participants who underwent vaginal birth who were at least 37 weeks of gestation. Cases were defined by either a 1000 mL or greater blood loss or instances of heavier bleeding where parturients were given additional uterotonic treatment due to uterine atony. Controls were matched to cases on primiparity and labor induction status. Genotype was measured from a maternal blood sample obtained during the 2^nd postpartum month from 95 participants. Statistical analysis included bivariate tests and generalized linear and Poisson regression modeling.

RESULTS

The distribution of the genotype across the sample of 95 participants was 40% GG (n = 38), 50.5% AG (n = 48) and 9.5% AA (n = 9). Blood loss of 1000 mL or greater occurred at a rate of 7.9% for GG, 12.5% for AG and 55.6% for AA participants (p = 0.005). Multivariable models demonstrated A-carriers (versus GG) had 275.2 mL higher blood loss (95% CI 96.9-453.4, p < 0.01) controlling for parity, intrapartum oxytocin, self-reported ancestry, active management of third stage or genital tract lacerations. Furthermore, A-carrier individuals had a 79% higher risk for needing at least one second-line treatment (RR = 1.79, 95% CI = 1.08-2.95) controlling for covariates. Interaction models revealed that A-carriers who required no oxytocin for labor stimulation experienced 371.4 mL greater blood loss (95% CI 196.6-546.2 mL).

CONCLUSIONS

We provide evidence of a risk allele in the oxytocin receptor gene that may be involved in the development of postpartum hemorrhage among participants undergoing vaginal birth, particularly among those with fewer risk factors. The findings, if reproducible, could be useful in studying pharmacogenomic strategies for predicting, preventing or treating postpartum hemorrhage.

Continued versus discontinued oxytocin after the active phase of labor: An updated systematic review and meta-analysis

Objective

To systematically assess the effect of discontinued vs continued oxytocin after active stage of labour is established.

Methods

Pubmed, Embase, and the Cochrane Library were systematically searched to 18 April 2021. The risk ratio or mean difference with corresponding 95% confidence interval were computed to investigate the effect of intervention or control on maternal and fetus outcomes. This review was registered in the International Prospective Register of Systematic Reviews: CRD42021249635.

Results

Discontinuing oxytocin when the active labour was established might decrease the risk of cesarean delivery [RR (95% CI): 0.84 (0.72–0.98), P = 0.02]. However, when we restricted our analysis to women who performed cesarean section after the active phase was reached, the difference was no longer significant [RR (95% CI): 0.82 (0.60–1.10), P = 0.19]. The incidence of uterine tachysystole [RR (95% CI): 0.36 (0.27–0.49)], postpartum hemorrhage [RR (95% CI): 0.78 (0.65–0.93)], and non-reassuring fetal heart rate [RR (95% CI): 0.66 (0.58–0.76)] were significantly lower in the oxytocin discontinuation group. We also found a possible decrease in the risk of chorioamnionitis in discontinued oxytocin group [RR (95% CI): 2.77 (1.02–5.08)]. An increased duration of active [MD (95% CI): 2.28 (2.86–41.71)] and second [MD (95% CI): 5.36 (3.18–7.54)] phase of labour was observed in discontinued oxytocin group, while the total delivery time was not significantly different [MD (95% CI): 20.17 (-24.92–65.26)].

Conclusion

After the active labor is reached, discontinuation of oxytocin could be considered a new recommendation for the improved maternal and fetal outcomes without delaying labour.

Comparison of delivery outcomes in low-dose and high-dose oxytocin regimens for induction of labor following cervical ripening with a balloon catheter: A retrospective observational cohort study

A variety of oxytocin regimens are used for labor induction and augmentation. Considering the increasing rates of labor induction, it is important to assess the most optimal oxytocin regimen without compromising maternal and fetal safety. The aim of this study was to compare delivery outcomes of low-dose and high-dose oxytocin induction protocols. This retrospective cohort study of 487 women comparing low-dose oxytocin protocol (n = 280) and high-dose oxytocin protocol (n = 207) in labor induction following cervical ripening by balloon catheter was performed in Helsinki University Hospital after implementation of a new oxytocin induction protocol. The study included two six-month cohorts from 2016 and 2019. Women with vital singleton pregnancies ≥37 gestational weeks, cephalic presentation, and intact amniotic membranes were included. The primary outcome was the rate of vaginal delivery. The secondary outcomes were the rates of maternal and neonatal infections, postpartum hemorrhage, umbilical artery blood pH-value, admission to neonatal intensive care, and induction-to-delivery interval. Statistical analyses were performed by using IBM SPSS Statistics for Windows (Armonk, NY, USA). The rate of vaginal delivery was higher [69.9% (n = 144) vs. 47.9% (n = 134); p<0.004] and the rates of maternal and neonatal infection were lower during the new high-dose oxytocin protocol [maternal infections 13.6% (n = 28) vs. 22.1% (n = 62); p = 0.02 and neonatal infection 2.9% (n = 6) vs. 14.6% (n = 41); p<0.001, respectively]. The rates of post-partum hemorrhage, umbilical artery blood pH-value <7.05 or neonatal intensive care admissions did not differ between the cohorts. The median induction-to-delivery interval was shorter in the new protocol [32.0 h (IQR 18.5–42.7) vs. 37.9 h (IQR 27.8–52.8); p<0.001]. In conclusion, implementation of the new continuous high-dose oxytocin protocol resulted in higher rate of vaginal delivery and lower rate of maternal and neonatal infections. Our experience supports the use of high-dose continuous oxytocin induction regimen with a practice of stopping oxytocin once active labor is achieved, and a 15–18-hour maximum duration for oxytocin induction in the latent phase of labor following cervical ripening with a balloon catheter.

Iron Deficiency Anaemia and Atonic Postpartum Haemorrhage Following Labour

The purpose of this retrospective cohort study is to determine if iron deficiency anaemia (IDA) is associated with increased atonic postpartum haemorrhage (PPH) following labour. Women with singleton pregnancy carried to 24 or more weeks gestation, who were delivered under our care from 1997 to 2019, constituted the study population. A diagnosis of IDA was based on the finding of haemoglobin <10 g/dL and serum ferritin <15 μg/L in the absence of haemoglobinopathies. Women with elective caesarean section were excluded. Maternal characteristics, use of oxytocin, labour outcome and occurrence of PPH were compared between women with and without a diagnosis of IDA. The 1032 women (0.86%) with IDA exhibited slightly but significantly different maternal characteristics and had significantly higher incidence of total (4.5% versus 3.2%, p = 0.024) and atonic PPH (3.1% versus 2.0%, p = 0.011) despite similar incidences of labour induction, augmentation, and instrumental and intrapartum caesarean delivery. Multivariate analysis with adjustment for the effects of age, body mass index, height, parity, abortion history, labour induction and augmentation, instrumental delivery and infant macrosomia demonstrated that IDA was independently associated with total PPH (adjusted relative risk, aRR: 1.455, 95% confidence ratio, CI: 1.040-2.034) and atonic PPH (aRR: 1.588, 95% CI: 1.067-2.364). Our results indicate that despite the low prevalence in our population, IDA was independently associated with atonic PPH, probably consequent to placental adaptive changes in the presence of IDA. The correction and prevention of IDA could be the most important measure in countering the rising global prevalence of atonic PPH.

American College of Nurse-Midwives Clinical Bulletin Number 18: Induction of Labor

Induction of labor is an increasingly common component of intrapartum care in the United States. This rise is fueled by a nationwide escalation in both medically indicated and elective inductions at or beyond term, supported by recent research showing some benefits of induction over expectant management. However, induction of labor medicalizes the birth experience and may lead to a complex cascade of interventions. The purpose of this Clinical Bulletin is twofold: (1) to guide clinicians on the use of person-centered decision-making when discussing induction of labor and (2) to review evidence-based practice recommendations for intrapartum midwifery care during labor induction.

Naturally Occurring Genetic Variants in the Oxytocin Receptor Alter Receptor Signaling Profiles

The hormone oxytocin is commonly administered during childbirth to initiate and strengthen uterine contractions and prevent postpartum hemorrhage. However, patients have wide variation in the oxytocin dose required for a clinical response. To begin to uncover the mechanisms underlying this variability, we screened the 11 most prevalent missense genetic variants in the oxytocin receptor (OXTR) gene. We found that five variants, V45L, P108A, L206V, V281M, and E339K, significantly altered oxytocin-induced Ca²⁺ signaling or β-arrestin recruitment and proceeded to assess the effects of these variants on OXTR trafficking to the cell membrane, desensitization, and internalization. The variants P108A and L206V increased OXTR localization to the cell membrane, whereas V281M and E339K caused OXTR to be retained inside the cell. We examined how the variants altered the balance between OXTR activation and desensitization, which is critical for appropriate oxytocin dosing. The E339K variant impaired OXTR activation, internalization, and desensitization to roughly equal extents. In contrast, V281M decreased OXTR activation but had no effect on internalization and desensitization. V45L and P108A did not alter OXTR activation but did impair β-arrestin recruitment, internalization, and desensitization. Molecular dynamics simulations predicted that V45L and P108A prevent extension of the first intracellular loop of OXTR, thus inhibiting β-arrestin binding. Overall, our data suggest mechanisms by which OXTR genetic variants could alter clinical response to oxytocin.

Literature Review: Physiological Management for Preventing Postpartum Hemorrhage

The aim of this paper was to summarize the existing literature regarding postpartum hemorrhage (PPH) and its physiological management (i.e., skin-to-skin contact and breastfeeding). The background surrounding PPH and the role of skin-to-skin contact (SSC) and breastfeeding (BF) in PPH are identified, and these interventions are supported as a crucial means of preventing or minimizing the incidence of PPH. Despite its importance, to the best of my knowledge, an evaluation of this relationship has not yet been undertaken. The narrative literature review approach was used to summarize topic related researches. The search included three databases: CINAHL, PubMed, and Google Scholar. All articles related to the role of SSC and BF in PPH were chosen from the different databases. The findings demonstrate that SSC and BF are cost-effective methods that could be considered practices for the prevention of PPH. Immediate Skin-to-skin contact (SSC) and breastfeeding (BF) are central mediators of the psychophysiological process during the first hour after delivery (the third and fourth stages of labor).

Risk Factors for Atonic Postpartum Hemorrhage: A Systematic Review and Meta-analysis

OBJECTIVE

To identify and quantify risk factors for atonic postpartum hemorrhage.

DATA SOURCES

PubMed, CINAHL, EMBASE, Web of Science, and and ClinicalTrials.gov databases were searched for English language studies with no restrictions on date or location. Studies included randomized trials, prospective or retrospective cohort studies, and case-control studies of pregnant patients who developed atonic postpartum hemorrhage and reported at least one risk factor.

METHODS OF STUDY SELECTION

Title, abstract, and full-text screening were performed using the Raayan web application. Of 1,239 records screened, 27 studies were included in this review. Adjusted or unadjusted odds ratios (ORs), relative risks, or rate ratios were recorded or calculated. For each risk factor, a qualitative synthesis of low and moderate risk of bias studies classifies the risk factor as definite, likely, unclear, or not a risk factor. For risk factors with sufficiently homogeneous definitions and reference ranges, a quantitative meta-analysis of low and moderate risk of bias studies was implemented to estimate a combined OR.

TABULATION, INTEGRATION, AND RESULTS

Forty-seven potential risk factors for atonic postpartum hemorrhage were identified in this review, of which 15 were judged definite or likely risk factors. The remaining 32 assessed risk factors showed no association with atonic postpartum hemorrhage or had conflicting or unclear evidence.

CONCLUSION

A substantial proportion of postpartum hemorrhage occurs in the absence of recognized risk factors. Many risk factors for atonic hemorrhage included in current risk-assessment tools were confirmed, with the greatest risk conferred by prior postpartum hemorrhage of any etiology, placenta previa, placental abruption, uterine rupture, and multiple gestation. Novel risk factors not currently included in risk-assessment tools included hypertension, diabetes, and ethnicity. Obesity and magnesium were not associated with atonic postpartum hemorrhage in this review.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, CRD42020157521.

Association between Receipt of Intrapartum Magnesium Sulfate and Postpartum Hemorrhage

Objective  The aim of the study is to investigate the association between intrapartum administration of magnesium sulfate in women with hypertensive disorders of pregnancy and postpartum hemorrhage. Study Design  This was a retrospective cohort study of women diagnosed with a hypertensive disorder of pregnancy who delivered singleton gestations >32 weeks at a single, large volume tertiary care center between January 2006 and February 2015. Women who received intrapartum magnesium sulfate for seizure prophylaxis were compared with women who did not receive intrapartum magnesium sulfate. The primary outcome was frequency of postpartum hemorrhage. Secondary outcomes included estimated blood loss, uterine atony, and transfusion of packed red blood cells. Bivariable analyses were used to compare the frequencies of each outcome. Multivariable logistic regression models examined the independent associations of magnesium sulfate with outcomes. Results  Of 2,970 women who met inclusion criteria, 1,072 (36%) received intrapartum magnesium sulfate. Women who received magnesium sulfate were more likely to be nulliparous, publicly insured, of minority race or ethnicity, earlier gestational age at delivery, and undergo labor induction. The frequency of postpartum hemorrhage was significantly higher among women who received magnesium sulfate compared with those who did not (12.4 vs. 9.3%, p  = 0.008), which persisted after controlling for potential confounders. Of secondary outcomes, there was no difference in estimated blood loss between women who did and did not receive magnesium sulfate (250 mL [interquartile range 250-750] vs. 250 mL [interquartile range 250-750], p  = 0.446). However, compared with women who did not receive magnesium sulfate, women who received magnesium sulfate had a greater frequency of uterine atony (8.9 vs 4.9%, p  < 0.001) and transfusion of packed red blood cells (2.0 vs. 0.8%, p  = 0.008). These differences persisted after controlling for potential confounders. Conclusion  Intrapartum magnesium sulfate administration to women with hypertensive disorders of pregnancy is associated with increased odds of postpartum hemorrhage, uterine atony, and red blood cell transfusion.

The Role of Skin-to-Skin Contact and Breastfeeding on Atonic Postpartum Hemorrhage

Objectives: were to (a) determine incidence of postpartum hemorrhage (PPH) in all women delivering between 2009 and 2015, and (b) determine the amount of Estimated Blood Loss (EBL) and duration of the third stage of labor in each subgroup for women with or without PPH, and (c) compare EBL and duration of 3rd stage of labor between subgroups in groups of women with or without PPH. Design: A retrospective chart review conducted using codes for atonic PPH. Setting: Records from a University based tertiary setting, 264 charts were reviewed and data from 154 charts were analyzed. One-way ANOVAs followed with post-hocs and a 2-way ANOVA were conducted. Results: PPH rate increased by 47.50% from 2009–2015. For women with PPH, EBL was lower in skin to skin contact (SSC) + Breastfeeding (BF) subgroup. For women without PPH, EBL was lower in SSC only subgroup. Third stage of labor duration was longer in women with PPH. Conclusions: Study confirmed the increasing trends of PPH due to uterine atony and proposed role of SSC and BF in decreasing EBL and shorten the duration of the 3rd stage of labor for PPH women, usefulness of SSC and BF as physiologic practices merit further study.

Incidences of Atonic Postpartum Hemorrhage and Related Risk Factors at a Tertiary Hospital in Saudi Arabia

Background: In 2017, there were 295,000 maternal deaths worldwide from preventable causes related to birth. The leading cause of maternal mortality is obstetric hemorrhage. In Saudi Arabia, a paucity of evidence about incidences of atonic Postpartum Hemorrhage (PPH) and related risk factors exists. Therefore, aims were to (a) identify incidences of atonic PPH from 2015 to 2018 (b) determine risk factors of atonic PPH in vaginal birth. Methods: Retrospective chart review with purposive sampling conducted revealed 386 charts, 220 (57%) vaginal birth and 166 (43%) caesarian section (CS). Logistic regression analysis was used. Results: Incidences of atonic PPH were 2.5% from 2015 to 2017, with the rate increasing by 12% from 2017 to 2018. In vaginal birth, significant associations between the severity of blood loss with epidural (F = 6.314, df = 1, p = 0.013), episiotomy (F = 4.38, df = 1, p = 0.038), induction of labor (IOL) (F = 1.224, df = 1, p = 0.004), and Interaction between IOL, AUG, and epidural (F = 7.24, df = 1, p = 0.041) found. Discussion: Increasing rate of atonic PPH confirmed. Epidural, episiotomy, induction of labor, and induction with augmentation are factors associated with severe atonic PPH in vaginal birth.

Poor uterine contractility and postpartum hemorrhage among low-risk women: A case-control study of a large-scale database from Japan

OBJECTIVE

To examine the association between the risk of postpartum hemorrhage (PPH) and poor uterine contractility, which is suggested by the characteristics of labor.

METHODS

This case-control study used cases recorded in the Japan Perinatal Registry database during the period 2013-2016. After exclusion of women with specified known risk factors for PPH, we enrolled 174 082 primiparas who had a full-term live singleton vaginal birth. Participants were classified into four classes according to the diagnosis of abnormal labor patterns and use of uterotonics. χ² tests were used to compare PPH cases with controls, and odds ratios (OR) were calculated by univariate and multivariate analyses.

RESULTS

Among the enrolled women, 10 508 (6.0%) had PPH. Abnormal labor patterns were significantly associated with an increased risk of PPH. Compared with women without any abnormal labor patterns who had not used uterotonics, women with abnormal labor patterns were at a significantly increased risk for PPH regardless of whether they had used uterotonics (adjusted OR 1.23, 95% confidence interval [CI] 1.10-1.37) or not (adjusted OR 1.30, 95% CI 1.23-1.37).

CONCLUSION

Our study suggests that among low-risk women with PPH, poor uterine contractility in labor could be a significant predisposing risk factor for PPH.

Magnesium sulfate and risk of postpartum uterine atony and hemorrhage: A meta-analysis

OBJECTIVES

Magnesium sulfate (MgSO₄) is among the most commonly used medications in labor and delivery units. It has been used as a mean to protect against eclampsia and a neuroprotective agent for fetuses at risk of preterm birth. In the present study we investigated its impact in the occurrence of postpartum uterine atony and hemorrhage.

METHODS

We searched the Medline, Scopus, EMBASE, Cochrane Central Register of Controlled Trials CENTRAL, Clinicaltrials.gov and Google Scholar databases for randomized trials and observational studies. Statistical analysis was performed with the Hartung-Knapp-Sidik-Jonkman model in RStudio using the meta package.

RESULTS

Twelve studies fitted the predetermined criteria and these involved 41,190 women of whom 10,565 (25.6 %) received MgSO_4. The meta-analysis revealed that the risk of postpartum uterine atony was similar among patients that received MgSO₄ and those that did not (OR 1.93, 95 % CI 0.78, 4.81). Estimated blood loss (SMD 0.04, 95 % CI -0.10, 0.18) as well as the risk of postpartum hemorrhage (OR 1.82, 95 % CI 0.99, 3.35) also did not differ. Subgroup analysis revealed that evidence drawn from observational studies indicates a significant effect of MgSO₄ on the odds of postpartum uterine atony and hemorrhage; however, randomized trials do not support this.

CONCLUSIONS

The results of our meta-analysis suggest that it is reasonable to consider MgSO4 in women at risk of delivering before the completion of its elimination half-life. However, physicians should be vigilant in cases at risk of postpartum hemorrhage as current data are very heterogeneous and should not be considered as definitive.

The effect of an oxytocin washout period on blood loss at cesarean delivery

Objectives Prolonged oxytocin exposure may result in increased blood loss during delivery. Our objective was to determine whether an oxytocin rest period before cesarean delivery had an impact on blood loss. Methods We performed a retrospective cohort study of women who underwent primary cesarean delivery after oxytocin augmentation. The primary outcome was change between pre- and postoperative hematocrit (Hct) in women with less than 60-min oxytocin rest period (<60 min) and greater than 60-min rest period (>60 min). Results There was no difference in demographic characteristics (age, BMI, or gestational age at delivery) between the two groups. Women in the >60 min group had a higher cumulative dose and longer duration of oxytocin administration. There was no significant difference in change in Hct between the two groups when controlling for these factors. Conclusions We did not find a significant correlation between the duration of the oxytocin rest period and blood loss. Oxytocin washout periods of greater than 60 min may not result in decreased blood loss at cesarean delivery, and thus, women may not benefit from such oxytocin washout periods.

Complications of Cesarean Birth: Clinical Recommendations for Prevention and Management

The increase in severe maternal morbidity and mortality in the United States correlates with a significant rise in U.S. cesarean birth rates from 5.5% in 1970 to a rate of 31.9% of all births in 2018, far beyond the World Health Organization goal of 10% to 15%. Three key contributors to maternal morbidity and mortality related to cesarean birth include complications of hemorrhage, surgical site infection, and venous thromboembolism. All women should be screened for risk factors associated with these major complications during the antepartum, intrapartum, and postpartum period to assure the availability of immediate resources based on the assessment. Implementing evidence-based maternity care safety bundles, toolkits, and protocols to manage these complications can reduce adverse outcomes.

Predicting Postpartum Hemorrhage After Low-Risk Vaginal Birth by Labor Characteristics and Oxytocin Administration

OBJECTIVE

To determine the odds of postpartum hemorrhage (PPH) in low-risk women who gave birth vaginally and were exposed to different durations and dosages of oxytocin across a range of labor durations during spontaneous or induced labor.

DESIGN

A retrospective cross-sectional analysis of data from the Consortium for Safe Labor.

SETTING

Data were gathered from 12 clinical institutions across the United States from 2002 to 2008.

PARTICIPANTS

After exclusion of high-risk conditions associated with PPH, we examined data from 27,072 women who gave birth vaginally.

METHODS

PPH was defined as estimated blood loss of greater than 500 ml at the time of birth and/or a diagnostic code for PPH before hospital discharge. We included covariates were if they were associated with oxytocin use and PPH and did not mediate oxytocin use. We used regression models to determine the likelihood of PPH overall and within the induced and spontaneous labor groups separately. We used subgroup analyses within specific durations of labor to clarify the findings.

RESULTS

The overall rate of PPH was 3.9%. Women with induced labor experienced PPH more frequently than women who labored spontaneously. Labor augmentation was associated with greater adjusted odds for PPH when oxytocin was infused for more than 4 hours. Longer duration of spontaneous labor and the second stage of labor did not change this association. Oxytocin use during labor induction increased the odds for PPH when administered for more than 7 hours. The odds further increased when induction lasted longer than 12 hours and/or the second stage of labor was longer than 3 hours.

CONCLUSION

Strategies for judicious oxytocin administration may help mitigate PPH in low-risk women having vaginal birth.

The Role of Oxytocin in Primary Cesarean Birth Among Low-Risk Women

INTRODUCTION

To examine whether there is a threshold of oxytocin exposure at which the risk for primary cesarean increases among women who are nulliparous with a term, singleton, vertex fetus (NTSV) and how oxytocin interacts with other risk factors to contribute to this outcome.

METHODS

This was a secondary analysis of the Consortium on Safe Labor data set that used a retrospective cohort study design. Women who met the criteria for NTSV who were not admitted for a prelabor cesarean and for whom oxytocin data were available, were included in the sample. Robust logistic regression was used to examine the association of oxytocin exposure with primary cesarean birth, while controlling for demographic and clinical risk factors and clustering by provider.

RESULTS

The sample comprised 17,331 women who were exposed to oxytocin during labor. The women were predominantly white non-Hispanic (59.2%) with an average (SD) gestational age of 39.4 (1.1) weeks and an 18.5% primary cesarean rate. Exposure to greater than 11,400-milliunits (mU) of oxytocin resulted in 1.6 times increased odds of primary cesarean birth compared with less than 11,400 mU (95% CI 1.01-2.6).

DISCUSSION

Exposure to greater than 11,400 mU of oxytocin in labor was associated with an increased odds of primary cesarean birth in NTSV women.

Robust Characterization of the Uterine Myoelectrical Activity in Different Obstetric Scenarios

Electrohysterography (EHG) has been shown to provide relevant information on uterine activity and could be used for predicting preterm labor and identifying other maternal fetal risks. The extraction of high-quality robust features is a key factor in achieving satisfactory prediction systems from EHG. Temporal, spectral, and non-linear EHG parameters have been computed to characterize EHG signals, sometimes obtaining controversial results, especially for non-linear parameters. The goal of this work was to assess the performance of EHG parameters in identifying those robust enough for uterine electrophysiological characterization. EHG signals were picked up in different obstetric scenarios: antepartum, including women who delivered on term, labor, and post-partum. The results revealed that the 10th and 90th percentiles, for parameters with falling and rising trends as labor approaches, respectively, differentiate between these obstetric scenarios better than median analysis window values. Root-mean-square amplitude, spectral decile 3, and spectral moment ratio showed consistent tendencies for the different obstetric scenarios as well as non-linear parameters: Lempel–Ziv, sample entropy, spectral entropy, and SD1/SD2 when computed in the fast wave high bandwidth. These findings would make it possible to extract high quality and robust EHG features to improve computer-aided assessment tools for pregnancy, labor, and postpartum progress and identify maternal fetal risks.

A Comparative Study of Vaginal Labor and Caesarean Section Postpartum Uterine Myoelectrical Activity

Postpartum hemorrhage (PPH) is one of the major causes of maternal mortality and morbidity worldwide, with uterine atony being the most common origin. Currently there are no obstetrical techniques available for monitoring postpartum uterine dynamics, as tocodynamometry is not able to detect weak uterine contractions. In this study, we explored the feasibility of monitoring postpartum uterine activity by non-invasive electrohysterography (EHG), which has been proven to outperform tocodynamometry in detecting uterine contractions during pregnancy. A comparison was made of the temporal, spectral, and non-linear parameters of postpartum EHG characteristics of vaginal deliveries and elective cesareans. In the vaginal delivery group, EHG obtained a significantly higher amplitude and lower kurtosis of the Hilbert envelope, and spectral content was shifted toward higher frequencies than in the cesarean group. In the non-linear parameters, higher values were found for the fractal dimension and lower values for Lempel-Ziv, sample entropy and spectral entropy in vaginal deliveries suggesting that the postpartum EHG signal is extremely non-linear but more regular and predictable than in a cesarean. The results obtained indicate that postpartum EHG recording could be a helpful tool for earlier detection of uterine atony and contribute to better management of prophylactic uterotonic treatment for PPH prevention.

Predicting Postpartum Hemorrhage After Vaginal Birth by Labor Phenotype

INTRODUCTION

Postpartum hemorrhage (PPH) is an important contributor to maternal morbidity and mortality. Predicting which laboring women are likely to have a PPH is an active area of research and a component of quality improvement bundles. The purpose of this study was to identify phenotypes of labor processes (ie, labors that have similar features, such as duration and type of interventions) in a cohort of women who had vaginal births, estimate the likelihood of PPH by phenotype, and analyze how maternal and fetal characteristics relate to PPH risk by phenotype.

METHODS

This study utilized the Consortium for Safe Labor dataset (2002-2008) and examined term, singleton, vaginal births. Using 16 variables describing the labor and birth processes, a latent class analysis was performed to describe distinct labor process phenotypes.

RESULTS

Of 24,729 births, 1167 (4.72%) women experienced PPH. Five phenotypes best fit the data, reflecting labor interventions, duration, and complications. Women who had shorter duration of admission after spontaneous labor onset (admitted in latent or active labor) had the lowest rate of PPH (3.8%-3.9%). The 2 phenotypes of labor progress characterized by women who had complicated prolonged labors (spontaneous or induced) had the highest rate of PPH (8.0% and 12.0%, respectively). However, the majority of PPH (n = 881, 75%) occurred in the phenotypes with fewer complications. Prepregnancy body mass index did not predict PPH. Overall, the odds of PPH were highest among nulliparous women (odds ratio [OR], 1.52; 95% CI, 1.30-1.77), as well as Black women (OR, 1.39; 95% CI, 1.13-1.73) and Hispanic women (OR, 1.85; 95% CI, 1.56-2.20). Within phenotypes, maternal race and ethnicity, nulliparity, macrosomia, hypertension, and depression were associated with increased odds of PPH.

DISCUSSION

Women who were classified into a lower-risk labor phenotype and still experienced PPH were more likely to be nulliparous, a person of color, or diagnosed with hypertension.

High fever after sublingual administration of misoprostol for treatment of post-partum haemorrhage: a hospital-based, prospective observational study in Argentina

Objective

To characterise the occurrence of fever (≥38.0°C) after treatment for post‐partum haemorrhage (PPH) with sublingual misoprostol 800 mcg in Latin America, where elevated rates of misoprostol’s thermoregulatory effects and recipients’ increased susceptibility to high fever have been documented.

Methods

A prospective observational study in hospitals in Argentina enrolled consenting women with atonic PPH after vaginal delivery, eligible to receive misoprostol. Corporal temperature was assessed at 30, 60, 90 and 120 min post‐treatment; other effects were recorded. The incidence of high fever ≥ 40.0°C (primary outcome) was compared to the rate observed previously in Ecuador. Logistic regressions were performed to identify clinical and population‐based predictors of misoprostol‐induced fever.

Results

Transient shivering and fever were experienced by 75.5% (37/49) of treated participants and described as acceptable by three‐quarters of women interviewed (35/47). The high fever rate was 12.2% (6/49), [95% Confidence Interval (CI) 4.6, 24.8], compared to Ecuador’s rate following misoprostol treatment (35.6% (58/163) [95% CI 28.3, 43.5], P = 0.002). Significant predictors of misoprostol‐induced fever (model dependent) were as follows: pre‐delivery haemoglobin < 11.0g/dl, rapid placental expulsion, and higher age of the woman. No serious outcomes were reported prior to discharge.

Conclusions

Misoprostol to treat PPH in Argentina resulted in a significantly lower rate of high fever than in Ecuador, although both are notably higher than rates seen elsewhere. A greater understanding of misoprostol’s side effects and factors involved in their occurrence, including genetics, will help alleviate concerns. The onset of shivering may be the simplest way to know if fever can also be expected.

Effects of Intermittent and Continuous Oxytocin Exposure on Myometrial Contractile Activity in Term-Pregnant Rats In Vitro

Continuous oxytocin exposure to augment labor contractions may cause receptor desensitization and further reduce the uterine response to oxytocin, resulting in an increased risk of uterine atony. This study aimed to investigate and compare the uterine response to continuous and intermittent oxytocin stimulation. We hypothesized that intermittent brief episodes of oxytocin separated by recovery periods rather than continuous oxytocin application improves subsequent uterine contractions. Myometrial strips were isolated from term-pregnant rats (22 days of gestation; n = 11), mounted in tissue bath chambers, and exposed to continuous oxytocin (5 nM) for 2 h or 6 repeated episodes of 10-min oxytocin exposure (5 nM) separated by 10 min of recovery period in Krebs solution. Contractile parameters (force amplitude, frequency, and integral force) significantly decreased during continuous oxytocin exposure compared with control (n = 11; P < 0.01). Interestingly, myometrial contractility significantly increased during subsequent short intermittent oxytocin exposure which was sustained for 6 h compared with control or continuous exposure (n = 11; P < 0.01). Brief intermittent oxytocin stimulations resulted in better uterine response and improved contractile force than continuous exposure, which may be attributed to attenuation of receptor desensitization or recovery of oxytocin receptor function following intermittent exposure. These findings would help maintain adequate strong contractions to avoid postpartum bleeding.

Evaluation of the implementation of a protocol for the restrictive use of oxytocin during spontaneous labor

INTRODUCTION

Use of oxytocin is associated with uterine hyperstimulation and postpartum hemorrhage with a dose-dependent effect. We aimed to evaluate the effect of the implementation of a protocol for the restrictive use of oxytocin during spontaneous labor on obstetric and neonatal outcomes.

MATERIAL AND METHODS

We performed an observational before-and-after study among 2174 women in spontaneous labor with a term singleton cephalic fetus. Obstetric and neonatal outcomes were compared according to the period, before (period A) and after (period B) the implementation of a protocol for the restrictive use of oxytocin.

RESULTS

1235 women were included in period A and 939 in period B. Compared to period A, the use of oxytocin during period B was significantly lower (45.5 vs. 35.1%, p<0.001) in both nulliparous (61.2 vs 54.6%, p=0.04) and multiparous women (34.0 vs. 21.1%, p<0.001). Labor was significantly longer in period B, both in nulliparous (6.7 vs. 7.9 h, p<0.01) and multiparous women (4.1 vs. 4.5 h, p<0.01). A lower frequency of uterine hyperstimulation (6.6 vs. 2.7%, p=0.01) was observed in period B. The odds of instrumental and cesarean delivery were not different between the periods (respectively adjusted odds ratio (AOR), 95% confidence interval (CI), 1.1(0.8-1.4); 1.2(0.8-1.8)) including for nulliparous women (respectively, 1.3(0.9-1.7); 1.3(0.8-1.9)).

DISCUSSION

Reducing the use of oxytocin during spontaneous labor through the implementation of a protocol may reduce the iatrogenic effects without increasing the risk of caesarean section but this implies longer duration of labor.

Risk factors for severe postpartum haemorrhage: A population-based retrospective cohort study

BACKGROUND

Severe postpartum haemorrhage (PPH) is a serious clinical problem that is increasing in incidence.

AIM

To identify risk factors for severe PPH.

MATERIALS AND METHODS

Population-based retrospective cohort study of all women who gave birth in Victoria in 2009-2013 using the validated Victorian Perinatal Data Collection. Three multivariable logistic regression models estimated the adjusted risk of severe PPH. Adjusted odds ratios (aOR) and their 95% confidence intervals are reported. The primary outcome was severe PPH (estimated blood loss of ≥1500 mL).

RESULTS

Severe PPH occurred in 1.4% of all births (n = 5122). Maternal characteristics significantly associated with severe PPH included: multiple pregnancy; older maternal age; overweight/obesity; first births. Other risk factors included placental complications, macrosomia, instrumental vaginal birth, third and fourth degree perineal lacerations, in-labour caesarean section, birth at a gestation other than 37-41 weeks, duration of labour 12 to <24 h, and use of oxytocin infusions in labour. Planned pre-labour caesarean section was associated with reduced odds of severe PPH. Severe PPH also occurred in 0.7% (n = 104) of women with none of the identified risk factors.

CONCLUSIONS

Numerous risk factors for severe PPH are identified but some cases are not modifiable or predictable. Limiting use of oxytocin infusions in labour to cases with clear indications, and strategies to prevent severe perineal lacerations would prevent some severe PPHs. Close surveillance of all women in the hours immediately following birth is crucial to detect and manage excessive blood loss and reduce severe PPH and associated morbidity.

Drug discovery strategies for the identification of novel regulators of uterine contractility

Preterm birth and postpartum hemorrhage are the leading causes of neonatal and maternal morbidities worldwide, respectively. Current clinically utilized tocolytics and uterotonics to manage these obstetric conditions are limited due to their off-target effects and/or lack of efficacy. Thus, an ideal tocolytic or uterotonic would be uterine-selective with rapid onset and long-duration efficacy. Here, we discuss strategies for the discovery of new therapeutic targets and compounds that regulate uterine contractility with the aforementioned properties.

Maternal plasma levels of oxytocin during physiological childbirth - a systematic review with implications for uterine contractions and central actions of oxytocin

BACKGROUND

Oxytocin is a key hormone in childbirth, and synthetic oxytocin is widely administered to induce or speed labour. Due to lack of synthetized knowledge, we conducted a systematic review of maternal plasma levels of oxytocin during physiological childbirth, and in response to infusions of synthetic oxytocin, if reported in the included studies.

METHODS

An a priori protocol was designed and a systematic search was conducted in PubMed, CINAHL, and PsycINFO in October 2015. Search hits were screened on title and abstract after duplicates were removed (n = 4039), 69 articles were examined in full-text and 20 papers met inclusion criteria. As the articles differed in design and methodology used for analysis of oxytocin levels, a narrative synthesis was created and the material was categorised according to effects.

RESULTS

Basal levels of oxytocin increased 3-4-fold during pregnancy. Pulses of oxytocin occurred with increasing frequency, duration, and amplitude, from late pregnancy through labour, reaching a maximum of 3 pulses/10 min towards the end of labour. There was a maximal 3- to 4-fold rise in oxytocin at birth. Oxytocin pulses also occurred in the third stage of labour associated with placental expulsion. Oxytocin peaks during labour did not correlate in time with individual uterine contractions, suggesting additional mechanisms in the control of contractions. Oxytocin levels were also raised in the cerebrospinal fluid during labour, indicating that oxytocin is released into the brain, as well as into the circulation. Oxytocin released into the brain induces beneficial adaptive effects during birth and postpartum. Oxytocin levels following infusion of synthetic oxytocin up to 10 mU/min were similar to oxytocin levels in physiological labour. Oxytocin levels doubled in response to doubling of the rate of infusion of synthetic oxytocin.

CONCLUSIONS

Plasma oxytocin levels increase gradually during pregnancy, and during the first and second stages of labour, with increasing size and frequency of pulses of oxytocin. A large pulse of oxytocin occurs with birth. Oxytocin in the circulation stimulates uterine contractions and oxytocin released within the brain influences maternal physiology and behaviour during birth. Oxytocin given as an infusion does not cross into the mother's brain because of the blood brain barrier and does not influence brain function in the same way as oxytocin during normal labour does.

Comparative analysis of myometrial and vascular smooth muscle cells to determine optimal cells for use in drug discovery

Novel therapeutic regulators of uterine contractility are needed to manage preterm labor, induce labor and control postpartum hemorrhage. Therefore, we previously developed a high-throughput assay for large-scale screening of small molecular compounds to regulate calcium-mobilization in primary mouse uterine myometrial cells. The goal of this study was to select the optimal myometrial cells for our high-throughput drug discovery assay, as well as determine the similarity or differences of myometrial cells to vascular smooth muscle cells (VSMCs)-the most common off-target of current myometrial therapeutics. Molecular and pharmacological assays were used to compare myometrial cells from four sources: primary cells isolated from term pregnant human and murine myometrium, immortalized pregnant human myometrial (PHM-1) cells and immortalized non-pregnant human myometrial (hTERT-HM) cells. In addition, myometrial cells were compared to vascular SMCs. We found that the transcriptome profiles of hTERT-HM and PHM1 cells were most similar (r = 0.93 and 0.90, respectively) to human primary myometrial cells. Comparative transcriptome profiling of primary human myometrial transcriptome and VSMCs revealed 498 upregulated (p ≤ 0.01, log2FC≥1) genes, of which 142 can serve as uterine-selective druggable targets. In the high-throughput Ca²⁺-assay, PHM1 cells had the most similar response to primary human myometrial cells in OT-induced Ca²⁺-release (E_max = 195% and 143%, EC₅₀ = 30 nM and 120 nM, respectively), while all sources of myometrial cells showed excellent and similar robustness and reproducibility (Z' = 0.52 to 0.77). After testing a panel of 61 compounds, we found that the stimulatory and inhibitory responses of hTERT-HM cells were highly-correlated (r = 0.94 and 0.95, respectively) to human primary cells. Moreover, ten compounds were identified that displayed uterine-selectivity (≥5-fold E_max or EC₅₀ compared to VSMCs). Collectively, this study found that hTERT-HM cells exhibited the most similarity to primary human myometrial cells and, therefore, is an optimal substitute for large-scale screening to identify novel therapeutic regulators of myometrial contractility. Moreover, VSMCs can serve as an important counter-screening tool to assess uterine-selectivity of targets and drugs given the similarity observed in the transcriptome and response to compounds.