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Introduction: Sufficient contractions are necessary for a successful delivery but each contraction temporarily constricts the oxygenated blood flow to the fetus. Individual fetal or placental characteristics determine how the fetus can withstand this temporary low oxygen saturation. However, only a few studies have examined the impact of uterine activity on neonatal outcome and even less attention has been paid to parturients' individual characteristics. Our objective was therefore to find out whether fetuses compromised by maternal or intrapartum risk factors are more vulnerable to excessive uterine activity., Material and Methods: Uterine contractile activity was assessed by intrauterine pressure catheters. Women (n = 625) with term singleton pregnancies and fetus in cephalic presentation were included in this secondary, blind analysis of a randomized controlled trial cohort. Intrauterine pressure as Montevideo units (MVU), contraction frequency/10 min and uterine baseline tone were calculated for 4 h prior to birth or the decision to perform cesarean section. Uterine activity in relation to umbilical artery pH linearly or ≤7.10 was used as the primary outcome. Need for operative delivery (either cesarean section or vacuum-assisted delivery) due to fetal distress was analyzed as a secondary outcome. In addition, belonging to vulnerable subgroups with, for example, chorioamnionitis, hypertensive or diabetic disorders, maternal smoking or neonatal birthweight <10th percentile were investigated as additional risk factors., Results: A linear decline in umbilical artery pH was seen with increasing intrauterine pressure in all deliveries (p < 0.001). Among parturients with suspected chorioamnionitis, every increasing 10 MVUs increased the likelihood of umbilical artery pH ≤7.10 (odds ratio [OR] 1.17, 95% confidence interval [CI] 1.02-1.34, p = 0.023). The need for operative delivery due to fetal distress was increased among all laboring women by every increasing 10 MVUs (OR 1.05, 95% CI 1.01-1.09, p = 0.015). This association with operative deliveries was further increased among parturients with hypertensive disorders (OR 1.23, 95% CI 1.05-1.43, p = 0.009) and among those with diabetic disorders (OR 1.13, 95% CI 1.04-1.28, p = 0.003)., Conclusions: Increasing intrauterine pressure impairs umbilical artery pH especially among parturients with suspected chorioamnionitis. Fetuses in pregnancies affected by chorioamnionitis, hypertensive or diabetic disorders are more vulnerable to high intrauterine pressure., (© 2024 The Authors. Acta Obstetricia et Gynecologica Scandinavica published by John Wiley & Sons Ltd on behalf of Nordic Federation of Societies of Obstetrics and Gynecology (NFOG).)

Objective: To investigate the impact of uterine contractile activity on the outcome of trial of labour after caesarean section (TOLAC)., Design: Secondary, blinded analyses of a prospective TOLAC cohort., Setting: Two labour wards, one in a university tertiary hospital and the other in a central hospital., Population: A total of 194 TOLAC parturients with intrauterine tocodynamometry during labour., Methods: Analysis of intrauterine pressure, frequency of contractions and baseline tonus of uterine muscle in 30-minute periods for 4 hours before birth., Main Outcome Measures: Primary outcome: uterine contractile activity during TOLAC. Secondary aims: contributors associated with failed TOLAC and uterine rupture., Results: TOLAC succeeded in 74% of cases. Uterine contractile activity, expressed as intrauterine pressure, was significantly higher in successful TOLAC compared with failed TOLAC (210 versus 170 Montevideo units). The statistically significant risk factors of failed TOLAC, after multivariate regression analysis, were prolonged gestational age, reduced cervical dilatation at admission and lower mean intrauterine pressure. In cases of uterine rupture, contractile activity did not differ from that in failed TOLAC. Cervical ripening with a Foley catheter appeared to be a risk factor for uterine rupture, as well as cervical dilatation <3 cm at admission. The incidence of total uterine rupture was 2.6% (n = 5)., Conclusions: Women with successful vaginal birth had higher uterine contractile activity than those experiencing failed TOLAC or uterine rupture despite similar use of oxytocin. Induction of labour with a Foley catheter turned out to be a risk factor for uterine rupture during TOLAC among parturients with no previous vaginal delivery., Tweetable Abstract: During VBAC the response to oxytocin, assessed as intrauterine pressure, is greater and adequate, in contrast to failed TOLAC., (© 2021 The Authors. BJOG: An International Journal of Obstetrics and Gynaecology published by John Wiley & Sons Ltd.)

Objective: To investigate whether the use of intrauterine tocodynamometry versus external tocodynamometry (IT versus ET) during labour reduces operative deliveries and improves newborn outcome. As IT provides more accurate information on labour contractions, the hypothesis was that it may more appropriately guide oxytocin use than ET., Design: Randomised controlled trial., Setting: Two labour wards, in a university tertiary hospital and a central hospital., Population: A total of 1504 parturients with singleton pregnancies, gestational age ≥37 weeks and fetus in cephalic position: 269 women with uterine scars, 889 nulliparas and 346 parous women with oxytocin augmentation., Methods: Participants underwent IT (n = 736) or ET (n = 768) during the active first stage of labour., Main Outcome Measures: Primary outcome: rate of operative deliveries., Secondary Outcomes: duration of labour, amount of oxytocin given, adverse neonatal outcomes., Results: Operative delivery rates were 26.9% (IT) and 25.9% (ET) (odds ratio 1.05, 95% CI 0.84-1.32, P = 0.663). The ET to IT conversion rate was 31%. We found no differences in secondary outcomes (IT versus ET). IT reduced oxytocin use during labours with signs of fetal distress, and trial of labour after caesarean section., Conclusions: IT did not reduce the rate of operative deliveries, use of oxytocin, or adverse neonatal outcomes, and it did not shorten labour duration., Tweetable Abstract: IT (versus ET) reduced oxytocin use in high-risk labours but did not influence operative delivery rate or adverse neonatal outcomes., (© 2020 Royal College of Obstetricians and Gynaecologists.)

Background: Purpose of this study was to investigate differences between primiparous term pregnancies, one leading to vaginal delivery (VD) and the other to acute cesarean section (CS) due to labor dystocia in the first stage of labor. We particularly wanted to assess the influence of body mass index (BMI) on CS risk., Methods: A retrospective case-control study in a tertiary delivery unit with 5200 deliveries annually. Cases were 296 term primiparous women whose intended vaginal labor ended in acute CS because of dystocia. Controls were primiparas with successful vaginal delivery VD (n = 302). The data were retrieved from medical records. Multiple logistic regression analyses were used to assess the associations between BMI and covariates on labor dystocia., Results: In the cases ending with acute CS, women were older (OR 1.06 [1.03-1.10]), shorter (OR 0.94 [0.91-0.96]) and more often had a chronic disease (OR 1.60 [1.1-2.29]). In this group fetal malposition (OR 42.0 [19.2-91.9]) and chorioamnionitis (OR 10.9 [5.01-23.6]) were more common, labor was less often in an active phase (OR 3.37 [2.38-4.76]) and the cervix was not as well ripened (1.5 vs. 2.5 cm, OR 0.57 [0.48-0.67] on arrival at the birth unit. BMI was higher in the dystocia group (24.1 vs. 22.6 kg/m 2 , p < 0.001), and rising maternal pre-pregnancy BMI had a strong association with dystocia risk. If BMI increased by 1 kg/m 2 , the risk of CS was 10% elevated. Among obese primiparas, premature rupture of membranes, chorioamnionitis and induction of labor were more common. Their labors were less often in an active phase at hospital admission. Severely obese primiparas (BMI ≥ 35 kg/m 2 ) had 4 hours longer labor than normal-weight parturients., Conclusions: Labor dystocia is a multifactorial phenomenon in which the possibility to ameliorate the condition via medical treatment is limited. Hospital admission at an advanced stage of labor is recommended. Pre-pregnancy weight control in the population at reproductive age is essential, as a high BMI is strongly associated with labor dystocia.