The effect of morbid obesity or advanced maternal age on oxytocin-induced myometrial contractions: an in vitro study

Oxytocin versus carbetocin at elective Cesarean delivery in parturients with class III obesity: a double-blind randomized controlled noninferiority trial

PURPOSE

Class III obesity (body mass index [BMI] ≥ 40 kg·m-2) is associated with high rates of Cesarean deliveries and postpartum hemorrhage, with increased maternal and fetal morbidity. The doses of oxytocin and carbetocin are two to four times higher at Cesarean delivery in patients with class III obesity. We sought to investigate the efficacy of carbetocin 80 µg iv compared with oxytocin 1 IU iv (plus infusion) at elective Cesarean delivery in parturients with class III obesity. We hypothesized that, with equipotent dosing, carbetocin would be noninferior to oxytocin.

METHODS

We conducted a randomized, double-blind, noninferiority study in nonlabouring, term parturients with BMI ≥ 40 kg·m-2 undergoing elective Cesarean delivery under neuraxial anesthesia. Patients received either a 1-IU bolus of oxytocin iv followed by an infusion of 4.8 IU·hr-1 or an 80-µg carbetocin bolus iv followed by a placebo infusion. Uterine tone was determined by palpation by the obstetrician at 3, 5, and 10 min, using a verbal numerical rating score of 0 (boggy) to 10 (firm). The primary outcome was uterine tone at 3 min. Secondary outcomes included uterine tone at 5 and 10 min, blood loss, additional uterotonics, and side effects.

RESULTS

Forty-seven participants were included in the analysis. Median tone at 3 min was similar for oxytocin (8; 95% confidence interval [CI], 7 to 8) and carbetocin (8; 95% CI, 8 to 9) (P = 0.06), with no difference at 5 and 10 min. Blood loss, side effects, and the need for additional uterotonics were not significantly different between the study groups.

CONCLUSION

We conclude that carbetocin is noninferior to oxytocin at elective Cesarean delivery in parturients with class III obesity, with the advantage of single bolus dosing without infusion.

STUDY REGISTRATION

ClinicalTrials.gov ( NCT04902729 ); first submitted 21 May 2021.

Maternal Body Mass Index, Myometrium Contractility and Uterotonic Receptor Expression in Pregnancy

Pregnant individuals with obesity (body mass index, BMI ≥ 30 kg/m2) are more likely to experience prolonged labor and have double the risk of cesarean compared with individuals with normal weight (BMI < 25 kg/m2). The aim of this study was to evaluate whether obesity in pregnancy is associated with reduced spontaneous and oxytocin-stimulated myometrial contractile activity using ex vivo preparations. We also assessed the relationship between maternal BMI and the expression of oxytocin (OXTR) and prostaglandin (FP) receptors in the myometrial tissue. We enrolled 73 individuals with a singleton gestation undergoing scheduled cesarean delivery at term in a prospective cohort study. This included 49 individuals with a pre-pregnancy BMI ≥ 30 kg/m2 and 24 with BMI < 25.0 kg/m2. After delivery, a small strip of myometrium was excised from the upper edge of the hysterotomy. Baseline spontaneous and oxytocin stimulated myometrial contractile activity was measured using ex vivo preparations. Additionally, expression of oxytocin and prostaglandin receptors from myometrial samples were compared using qRT-PCR and western blot techniques. Spontaneous and oxytocin-stimulated contraction frequency, duration, and force were not significantly different in myometrial samples from the obese and normal-weight individuals. Myometrial OXTR gene and protein expression was also similar in the two groups. While FP gene expression was lower in the myometrial samples from the obese group, protein expression did not differ. These data help to address an important knowledge gap related to the biological mechanisms underlying the association between maternal obesity and dysfunctional labor.

The minimum effective dose (ED90) of prophylactic oxytocin infusion during cesarean delivery in patients with and without obesity: an up-down sequential allocation dose-response study

BACKGROUND

Obesity is associated with greater oxytocin requirement during labor induction or augmentation. There are scant data exploring the intra-operative requirement during cesarean delivery in patients with obesity, and none comparing it with those without obesity. We evaluated the minimum effective dose (ED90) of an oxytocin infusion to achieve adequate uterine tone during cesarean delivery in patients with and without obesity.

METHODS

Patients (body mass index ≥30 kg/m2 represented patients with obesity) undergoing cesarean delivery using subarachnoid block were included. This prospective dual-arm dose-finding study used a 9:1 biased sequential allocation design. Oxytocin infusion was initiated at 13 IU/h at cord clamping in the first patient of each group. Uterine tone was graded as satisfactory or unsatisfactory by the obstetrician four minutes after initiation of the infusion. The dose of oxytocin infusion for subsequent patients was determined according to the response of the previous patient in the group. Oxytocin-associated side effects were evaluated. Dose-response data for the groups was evaluated using log-logistic function and ED90 estimates derived from fitted equations using the delta method.

RESULTS

The ED90 of oxytocin was significantly higher for patients with obesity (n = 40) compared with those without obesity (n = 40) [25.7 IU/h, 95% CI 18.6 to 32.9) vs. 16.6 IU/h, 95% CI 14.9 to 18.3)]; relative ratio 1.55 [95% CI 1.09 to 2.01] (P = 0.019).

CONCLUSIONS

Patients with obesity require a higher intra-operative oxytocin infusion dose rate to achieve a satisfactorily contracted uterus after fetal delivery when compared with patients without obesity.

Regulation of oxytocin-induced calcium transients and gene expression in engineered myometrial tissues by tissue architecture and matrix rigidity

The uterus is susceptible to benign tumors known as fibroids, which have been associated with many pregnancy complications, including preterm labor. However, the impact of fibrotic tissue remodeling on the physiology of the myometrium, the smooth muscle layer of the uterus, is poorly understood, in large part due to a lack of model systems. In this study, we engineered healthy-like and fibrotic-like myometrium by culturing human myometrial smooth muscle cells on polyacrylamide hydrogels micropatterned with fibronectin to independently tune matrix rigidity and tissue alignment, respectively. We then evaluated calcium transients in response to oxytocin stimulation. Isotropic myometrial tissues on stiff substrates (representing fibrotic myometrium) had shorter calcium transients due to shorter decay time compared to aligned myometrial tissues on soft substrates (representing healthy myometrium). Calcium transients in aligned tissues had longer response times and longer decay times than isotropic tissues, irrespective of substrate stiffness. The amplitude of calcium transients was also higher on soft substrates compared to stiff substrates, irrespective of tissue alignment. We also performed RNA sequencing to detect differentially expressed genes between healthy- and fibrotic-like tissues, which revealed that a bitter taste receptor shown to induce smooth muscle relaxation, TAS2R31, was down-regulated in fibrotic-like tissues. Finally, we measured oxytocin-induced calcium transients in response to pre-treatment with progesterone, caffeine, thrombin, and nifedipine to demonstrate applications for our model system in drug screening. Both progesterone and caffeine caused a decrease in calcium transient duration, as expected, while thrombin and nifedipine had less impact. Collectively, our engineered model of the myometrium enables new insights into myometrial mechanobiology and can be extended to identify or screen novel drug targets.

Oxytocin receptor DNA methylation is associated with exogenous oxytocin needs during parturition and postpartum hemorrhage

BACKGROUND

The oxytocin receptor gene (OXTR) is regulated, in part, by DNA methylation. This mechanism has implications for uterine contractility during labor and for prevention or treatment of postpartum hemorrhage, an important contributor to global maternal morbidity and mortality.

METHODS

We measured and compared the level of OXTR DNA methylation between matched blood and uterine myometrium to evaluate blood as an indicator of uterine methylation status using targeted pyrosequencing and sites from the Illumina EPIC Array. Next, we tested for OXTR DNA methylation differences in blood between individuals who experienced a postpartum hemorrhage arising from uterine atony and matched controls following vaginal birth. Bivariate statistical tests, generalized linear modeling and Poisson regression were used in the analyses.

RESULTS

Here we show a significant positive correlation between blood and uterine DNA methylation levels at several OXTR loci. Females with higher OXTR DNA methylation in blood had required significantly more exogenous oxytocin during parturition. With higher DNA methylation, those who had oxytocin administered during labor had significantly greater relative risk for postpartum hemorrhage (IRR 2.95, 95% CI 1.53-5.71).

CONCLUSIONS

We provide evidence that epigenetic variability in OXTR is associated with the amount of oxytocin administered during parturition and moderates subsequent postpartum hemorrhage. Methylation can be measured using a peripheral tissue, suggesting potential use in identifying individuals susceptible to postpartum hemorrhage. Future studies are needed to quantify myometrial gene expression in connection with OXTR methylation.

Advancing understanding of maternal age: correlating epigenetic clocks in blood and myometrium

Background:

Advanced maternal age is currently a term defined by chronological age. However, a group of biomarkers known as epigenetic clocks, which can predict morbidity and mortality, has been used to estimate measures of biological aging. Uterine myometrial function during the process of parturition may be influenced by aging, as labor dystocia, unplanned intrapartum cesarean birth, and postpartum hemorrhage are more common in older individuals. The purpose of this study was to evaluate the use of epigenetic clocks in maternal myometrium and blood for predicting age and to evaluate the correlation of epigenetic age between the tissues.

Results:

We compared epigenetic age in blood and myometrial samples provided by women undergoing planned cesarean birth at term gestation. Chronological age ranged from 20 to 50 with a median (IQR) age of 35.5(8) years. The MethylationEPIC BeadChip was used to obtain DNA methylation data, and then epigenetic age was calculated using the Horvath, Hannum, GrimAge, and PhenoAge clocks. Spearman correlations of epigenetic age with chronological age were calculated. We tested the relationship of epigenetic age in maternal blood to epigenetic age in myometrium. Age acceleration, for each clock, was also correlated between tissues. Twenty-seven participants provided samples, and 21 matched specimens were included in the final analysis after quality control. Spearman correlation between maternal chronological age and epigenetic age were significant in three of the four clocks (pan-tissue Horvath, Hannum, and GrimAge), for both myometrium and blood samples. Correlations between blood epigenetic age and maternal age ranged from 0.72 to 0.87 (all p < 0.001). Correlations between myometrial epigenetic age and maternal age were also significant (0.62–0.70, p = 0.002), though lower than correlations seen in blood. Maternal blood epigenetic age also correlated with epigenetic age in myometrium with each of these three clocks 0.60 (p = 0.004, Horvath), 0.63 (p = 0.003, Hannum), and 0.80 (p < 0.001, GrimAge). GrimAge age acceleration had the highest correlation between tissues among the clocks (0.49, p = 0.02).

Conclusions:

Given the limited sample, this study provides insight into the potential use of epigenetic age derived from blood as a proxy for myometrial epigenetic age, which may be a useful biomarker in estimating myometrial biological age in relationship to myometrial dysfunction. GrimAge outperformed the other tested clocks in terms of concordance of epigenetic age and age acceleration between tissues; however, the Horvath and Hannum clocks may be useful depending on the outcome of interest in pregnancy.

Association of serum leptin at 24-28 weeks gestation with initiation and progression of labor in women

Concentrations of the hormone leptin, which is produced by adipose tissue, increase with increasing BMI, whereas leptin sensitivity often declines with higher BMI. Thus, altered leptin signaling may play a role in reproductive health risks observed with increasing BMI, which include later onset and slow progression of labor. Conflicting evidence from clinical, animal and in vitro studies have suggested that leptin either promotes or inhibits labor. We hypothesized that serum leptin concentrations or serum leptin: body mass index (BMI) ratios in women may be associated with the initiation and progression of labor. Following informed consent, serum samples were collected from 90 women with singleton pregnancies at the time of routine glucose-challenge testing, for measurement of leptin. The potential influence of leptin on gestation length and cervical dilation timing were examined by multiple linear regression. Data were analyzed from 63 participants who met exclusion and inclusion criteria. Leptin concentrations (log-transformed) at 24–28 weeks gestation were not significantly correlated with first trimester BMI . Log serum leptin and leptin: BMI ratio each were significantly associated with shorter total gestation length in uncomplicated, term pregnancies. In contrast, the mid-pregnancy leptin concentrations were not associated with progression of labor, assessed by cervical dilation over time. The association between higher serum leptin and shorter gestation length is consistent with the hypothesis that leptin promotes, or is permissive for, the onset of labor.

The Impact of Obesity on the Management and Outcomes of Postpartum Hemorrhage

OBJECTIVE

The study aimed to evaluate the impact of obesity on the management and outcomes of postpartum hemorrhage.

STUDY DESIGN

We conducted a retrospective cohort study of women who delivered at a tertiary care center between February 1, 2013 and January 31, 2014 and experienced a postpartum hemorrhage. Charts were reviewed for clinical and sociodemographic data, and women were excluded if the medical record was incomplete. Hemorrhage-related severe morbidity indicators included blood transfusion, shock, renal failure, transfusion-related lung injury, cardiac arrest, and use of interventional radiology procedures. Obese (body mass index [BMI] ≥ 30 kg/m²) and nonobese women were compared. Data were analyzed using Chi-square, Student's t-test, Mann-Whitney U test, and linear regression where appropriate. The p-value <0.05 was significant.

RESULTS

Of 9,890 deliveries, 2.6% (n = 262) were complicated by hemorrhage. Obese women were more likely to deliver by cesarean section (55.5 vs. 39.8%, p = 0.016), undergo a cesarean after labor (31.1 vs. 12.2%, p = 0.001), and have a higher quantitative blood loss (1,313 vs. 1,056 mL, p = 0.003). Both groups were equally likely to receive carboprost, methylergonovine, and misoprostol, but obese women were more likely to receive any uterotonic agent (95.7 vs. 88.9%, p = 0.007) and be moved to the operating room (32.3 vs. 20.4, p = 0.04). There was no difference in the use of intrauterine pressure balloon tamponade, interventional radiology, or decision to proceed with hysterectomy. The two groups were similar in time to stabilization. There was no difference in the need for blood transfusion. Obese women required more units of blood transfused (2.2 ± 2 vs. 2 ± 5 units, p = 0.023), were more likely to have any hemorrhage-related severe morbidity (34.1 vs. 25%, p = 0.016), and more than one hemorrhage related morbidity (17.1 vs. 7.9, p = 0.02). After controlling for confounding variables, quantitative blood loss, and not BMI was predictive of the need for transfusion.

CONCLUSION

Despite similar management, obese women were more likely to have severe morbidity and need more units of blood transfused.

KEY POINTS

· Obese women were more likely to have a higher quantitative blood loss and require more units of blood transfused.. · Obese women were more likely to experience any hemorrhage-related severe morbidity.. · Although obese women were more likely to be moved to the operating room for intervention, the rates of intrauterine pressure balloon tamponade, interventional radiology or hysterectomy were the same for obese and non-obese women..

Refractory uterine atony: still a problem after all these years

Postpartum hemorrhage is a leading cause of maternal morbidity and mortality, and uterine atony is the leading cause of postpartum hemorrhage. Risk factors for uterine atony include induced or augmented labor, preeclampsia, chorio-amnionitis, obesity, multiple gestation, polyhydramnios, and prolonged second stage of labor. Although a risk assessment is recommended for all parturients, many women with uterine atony do not have risk factors, making uterine atony difficult to predict. Oxytocin is the first-line drug for prevention and treatment of uterine atony. It is a routine component of the active management of the third stage of labor. An oxytocin bolus dose as low as 1 IU is sufficient to produce satisfactory uterine tone in almost all women undergoing elective cesarean delivery. However, a higher bolus dose (3 IU) or infusion rate is recommended for women undergoing intrapartum cesarean delivery. Carbetocin, available in many countries, is a synthetic oxytocin analog with a longer duration than oxytocin that allows bolus administration without an infusion. Second line uterotonic agents include ergot alkaloids (ergometrine and methylergonovine) and the prostaglandins, carboprost and misoprostol. These drugs work by a different mechanism to oxytocin and should be administered early for uterine atony refractory to oxytocin. Rigorous studies are lacking, but methylergonovine and carboprost are likely superior to misoprostol. Currently, the choice of second-line agent should be based on their adverse effect profile and patient comorbidities. Surgical and radiologic management of uterine atony includes uterine tamponade using balloon catheters and compression sutures, and percutaneous transcatheter arterial embolization.

Predicting factors of failed induction of labor in three hospitals of Southwest Ethiopia: a cross-sectional study

Introduction

Failed induction of labor affects maternal and neonatal outcomes as well as the cost of healthcare, especially in low-resource setting regions in which the prevalence of failed induction is higher despite the incidence of labor induction is low. This study aimed to assess the prevalence of failed induction of labor in southwest Ethiopia.

Method

A hospital-based cross-sectional study was conducted among 441 induced women from March 1 to August 30, 2018. A systematic random sampling technique was used to select study participants. Data were collected using a pretested and structured questionnaire. Bivariable and multivariable logistic regression models were done and fitted to identify predictors of failed induction. An adjusted odds ratio with 95% confidence interval (CI) was calculated to determine the level of significance.

Result

Premature rupture of membrane was the most common cause of labor induction and the commonly used method of labor induction were oxytocin infusion. Cesarean section was done for 28.1% of induced women. Failed induction of labor was found to be 21%. Primiparous [AOR = 2.35 (1.35–4.09)], analgesia/anesthesia [AOR = 4.37 (1.31–14.59)], poor Bishop Score [AOR = 2.37 (1.16–4.84)], Birth weight ≥ 4 k grams [AOR = 2.12 (1.05–4.28)] and body mass index [AOR = 5.71 (3.26–10.01)] were found to be significantly associated with failed induction of labor.

Conclusion

The prevalence of failed induction of labour was found to be high. Preparation of the cervix before induction in primi-parity women is suggested to improve the success of induction. To achieve the normal weight of women and newborns, proper nutritional interventions should be given for women of reproductive age. It is better to use analgesia/anesthesia for labor induction when it becomes mandatory and there are no other optional methods of no- pharmacologic pain management.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-03862-x.

Oxytocin at elective caesarean delivery: a dose-finding study in women with obesity

Prophylactic oxytocin administration at the third stage of labour reduces blood loss and the need for additional uterotonic drugs. Obesity is known to be associated with an increased risk of uterine atony and postpartum haemorrhage. It is unknown whether women with obesity require higher doses of oxytocin in order to achieve adequate uterine tone after delivery. The purpose of this study was to establish the bolus dose of oxytocin required to initiate effective uterine contraction in 90% of women with obesity (the ED₉₀ ) at elective caesarean delivery. We conducted a double-blind dose-finding study using the biased coin up-down design method. Term pregnant women with a BMI ≥ 40 kg.m^-2 undergoing elective caesarean delivery under regional anaesthesia were included. Those with conditions predisposing to postpartum haemorrhage were not included. Oxytocin was administered as an intravenous bolus over 1 minute upon delivery of the fetus. With the first woman receiving 0.5 IU, oxytocin doses were administered according to a sequential allocation scheme. The primary outcome measure was satisfactory uterine tone, as assessed by the operating obstetrician 2 minutes after administration of the oxytocin bolus. Secondary outcomes included the need for rescue uterotonic drugs, adverse effects and estimated blood loss. We studied 30 women with a mean (SD) BMI of 52.3 (7.6) kg.m^-2 . The ED₉₀ for oxytocin was 0.75 IU (95%CI 0.5-0.93 IU) by isotonic regression and 0.78 IU (95%CI 0.68-0.88 IU) by the Dixon and Mood method. Our results suggest that women with a BMI ≥ 40 kg.m^-2 require approximately twice as much oxytocin as those with a BMI < 40 kg.m^-2 , in whom an ED₉₀ of 0.35 IU (95%CI 0.15-0.52 IU) has previously been demonstrated.