Sonographic landmarks to differentiate “false labor” and “early true labor” as a possible new application of ultrasound in labor ward

Assessment of utero-cervical angle and cervical length as predictors for threatened preterm delivery in singleton pregnancies

OBJECTIVES

The aim of this study was to evaluate the relationship between the cervix and the threat of preterm labor in singleton pregnancies between gestational weeks less than 37 and greater than 37 weeks in correlation with utero-cervical angle (UCA) and cervical length (CL) measurements.

MATERIALS AND METHODS

We conducted a prospective cohort study with UCA and CL measurements in patients with threatened preterm labor (TPL). Primary outcome was differences in UCA and CL measurements in relationship to maternal characteristics and perinatal outcome between groups. Secondary outcome evaluated measurement results and influencing factors for delivery within 7 days, between 1 and 4 weeks and beyond 4 weeks.

RESULTS

Overall 152 patients were divided into as study/preterm group (<37 weeks; n = 56) and the control/term group (≥37 weeks; n = 96). Mean gestational age at admission was similar in both groups (30.98 ± 2.83 vs. 30.36 ± 2.63 weeks, p = 0.149) with similar CL (33.9 ± 6.34 vs. 32.02 ± 8.88 mm, p = 0.132), but wider UCA in the preterm group (81.65 ± 16.81° vs. 99.21 ± 22.33°, p < 0.001). Multivariate logistic regression analysis for preterm delivery was significant for nulliparity and UCA measurement. The factor for delivering before 37 gestational weeks within 7 days was the gestational week at admission (p = 0.046). UCA and CL measurements were statistically significant for distinguishing patients for delivery within 7 days and beyond 4 weeks (p = 0.001 for CL and p = 0.0001 for UCA). NPV was found 92.5, 92.2, and 92.3 for UCA >105°, CL ≤30 mm, and Bishop score >3, respectively.

CONCLUSION

Combined measurement of TV UCA and CL represents stronger predictors for sPTB ultrasonographically, demonstrating the uterocervical sub-segment maturation before the active onset of labor.

The latent phase of labor

The latent phase of labor extends from the initiation of labor to the onset of the active phase. Because neither margin is always precisely identifiable, the duration of the latent phase often can only be estimated. During this phase, the cervix undergoes a process of rapid remodeling, which may have begun gradually weeks before. As a consequence of extensive changes in its collagen and ground substance, the cervix softens, becomes thinner and dramatically more compliant, and may dilate modestly. All of these changes prepare the cervix for the more rapid dilatation that will occur during the active phase to follow. For the clinician, it is important to recognize that the latent phase may normally extend for many hours. The normal limit for the duration of the latent phase should be considered to be approximately 20 hours in a nullipara and 14 hours in a multipara. Factors that have been associated with a prolonged latent phase include deficient prelabor or intrapartum cervical remodeling, excessive maternal analgesia or anesthesia, maternal obesity, and chorioamnionitis. Approximately 10% of women with a prolonged latent phase are actually in false labor, and their contractions eventually abate spontaneously. The management of a prolonged latent phase involves either augmenting uterine activity with oxytocin or providing a sedative-induced period of maternal rest. Both are equally effective in advancing the labor to active phase dilatation. A very long latent phase may be a harbinger of other labor dysfunctions.

The Novel Ultrasonographic Marker of Uterocervical Angle for Prediction of Spontaneous Preterm Birth in Singleton and Twin Pregnancies: A Systematic Review and Meta-Analysis

The alteration of the uterocervical angle (UCA) has been proposed to play an important role in spontaneous preterm birth (sPTB). The aim of this systematic review and meta-analysis was to evaluate the evidence on the UCA predictive role in sPTB. In this study, PubMed, Web of Science, Scopus, and Google scholar were systematically searched from inception up to June 2020. Inter-study heterogeneity was also assessed using Cochrane's Q test and the I2 statistic. Afterward, the random-effects model was used to pool the weighted mean differences (WMDs) and the corresponding 95% confidence intervals (CIs). Eleven articles that reported second-trimester UCA of 5,061 pregnancies were included in this study. Our meta-analysis results indicate that a wider UCA significantly increases the risk of sPTB in following cases: all pregnancies (WMD = 15.25, 95% CI: 11.78-18.72, p < 0.001; I2 = 75.9%, p < 0.001), singleton (WMD = 14.43, 95% CI: 8.79-20.06, p < 0.001; I2 = 82.4%, p < 0.001), and twin pregnancies (WMD = 15.14, 95% CI: 13.42-16.87, p < 0.001; I2 = 0.0%, p = 0.464). A wider ultrasound-measured UCA in the second trimester seems to be associated with the increased risk of sPTB in both singleton and twin pregnancies, which reinforces the clinical evidence that UCA has the potential to be used as a predictive marker of sPTB.

Uterocervical angle: an ultrasound screening tool to predict satisfactory response to labor induction

Background: A wide uterocervical angle >95° detected during the second trimester was associated with an increased risk for spontaneous preterm birth.Objective: We aimed to determine whether an ultrasonographic marker, uterocervical angle, correlates with satisfactory response to labor induction.Study design: We conducted a prospective cohort study from May 2016 through December 2017 of singleton term gestations undergoing transvaginal ultrasound for cervical length screening and uterocervical angle measurement. Uterocervical angle was measured between the lower uterine segment and the cervical canal. Latent phase duration >720 min was accepted to be a prolonged latent phase. The primary outcome was a prediction of satisfactory response to labor induction (latent phase duration <720 min).Results: Both anterior uterocervical angle (AUC = 0.802, p < .001) and the cervical length (AUC = 0.679, p < .05) significantly predicted satisfactory response to labor induction. Optimal cutoff value was obtained at the value of 97° (64% sensitivity, 91% specificity) for anterior uterocervical angle and 27 mm (64% sensitivity, 64% specificity) for the cervical length. Kaplan-Meier survival analysis showed that duration from labor induction to delivery was significantly higher in a group with longer cervical length (p = .04), additionally labor induction to delivery time was significantly higher in a group with lower UCA (p = .04).Conclusions: Both the cervical length and anterior uterocervical length were predictors for the satisfactory response to labor induction, and both parameters were found to be significantly associated with time from induction to delivery in survival analysis.

Can uterocervical angles successfully predict induction of labor in nulliparous women?

PURPOSE

Induction of labor is a common practice in obstetrics. In recent years, a newer ultrasonographic parameter called the uterocervical angle (UCA) has been identified as a predictive tool for births. Our purpose is to investigate the role of UCA in predicting successful induction of labor.

METHODS

The nulliparous term pregnancies (n:150) were grouped into successful/failed inductions of labor based on their progress into the active phase of labor after the administration of prostaglandin E2 (dinoprostone). The pre-induction cervical length (CL) and UCA were compared in the two groups. The study population was further grouped according to their modes of delivery and pre-induction UCAs were compared among the subgroups.

RESULTS

The mean UCAs were not significant among the successful induction and failed induction groups (105.46 ± 20.54 degrees in the successful group and 110.57 ± 13.46 degrees in the failed group). However, UCAs significantly varied among the modes of delivery subgroups. The median UCA was significantly higher in patients who delivered vaginally after a successful induction of labor than in patients who delivered via cesarean section. The median UCA value was lowest in patients who had a successful induction of labor but ended up having a cesarean section (Fig. 2). Further, the duration of the active phase of labor negatively correlated with the UCA but not the CL (rho=-0.23, p = 0.02). There was also a negative correlation between the CL and the UCA in patients who delivered vaginally after successful induction of labor (rho= -0.21, p = 0.03).

CONCLUSION

The UCA is a promising ultrasonographic marker in obstetrics. Although the pre-induction UCA did not predict the outcome of labor induction, patients with broader pre-induction UCAs were prone to have a shorter duration of active phase. The pre-induction CL and UCA are inversely corraleted in nulliparous women who delivered vaginally after a successful induction of labor.