BACKGROUND: Both short and long interpregnancy intervals are associated with adverse pregnancy outcomes; however, the impact of interpregnancy intervals on labor progression is unknown.
OBJECTIVE: We examined the impact of interpregnancy intervals on the labor curve, hypothesizing that those with a longer interpregnancy intervals would have slower labor progression.
METHODS: This is a retrospective cohort study of patients with a history of one prior vaginal delivery admitted for induction of labor or spontaneous labor with a singleton gestation ≥37 weeks at an academic medical center between 2004 and 2015. Repeated measures regression was used to construct labor curves, which were compared between patients with short interpregnancy intervals, defined as <3 years since the last delivery, and long interpregnancy intervals, defined as >3 years since the last delivery. We chose this interval as it approximates the median birth interval in the United States. Interval-censored regression was used to estimate the median duration of labor after 4 centimeters of dilation, stratified by type of labor (spontaneous vs induced). Multivariate analysis was used to adjust for potential confounders.
RESULTS: Of the 1331 patients who were included in the analysis, 544 (41%) had a long interpregnancy interval. Among the entire cohort, there were no significant differences in first or second-stage progression between short and long interpregnancy interval groups. In the stratified analysis, first-stage progression varied between groups on the basis of labor type: long interpregnancy interval was associated with a slower active phase among those being induced and a quicker active phase among those in spontaneous labor. The second-stage duration was similar between cohorts regardless of labor type.
CONCLUSIONS: Multiparas with an interpregnancy interval >3 years may have a slower active phase than those with a shorter interpregnancy interval when undergoing induction of labor. Interpregnancy interval does not demonstrate an effect on the length of the second stage.

The diagnosis of failure to progress, the most common indication for intrapartum cesarean delivery, is based on the assessment of cervical dilation and station over time. Labor curves serve as references for expected changes in dilation and fetal descent. The labor curves of Friedman, Zhang et al, and others are based on time alone and derived from mothers with spontaneous labor onset. However, labor induction is now common, and clinicians also consider other factors when assessing labor progress. Labor curves that consider the use of labor induction and other factors that influence labor progress have the potential to be more accurate and closer to clinical decision-making.
This study aimed to compare the prediction errors of labor curves based on a single factor (time) or multiple clinically relevant factors using two modeling methods: mixed-effects regression, a standard statistical method, and Gaussian processes, a machine learning method.
This was a longitudinal cohort study of changes in dilation and station based on data from 8022 births in nulliparous women with a live, singleton, vertex-presenting fetus ≥35 weeks of gestation with a vaginal delivery. New labor curves of dilation and station were generated with 10-fold cross-validation. External validation was performed using a geographically independent group. Model variables included time from the first examination in the 20 hours before delivery; dilation, effacement, and station recorded at the previous examination; cumulative contraction counts; and use of epidural anesthesia and labor induction. To assess model accuracy, differences between each model\'s predicted value and its corresponding observed value were calculated. These prediction errors were summarized using mean absolute error and root mean squared error statistics.
Dilation curves based on multiple parameters were more accurate than those derived from time alone. The mean absolute error of the multifactor methods was better (lower) than those of the single-factor methods (0.826 cm [95% confidence interval, 0.820-0.832] for the multifactor machine learning and 0.893 cm [95% confidence interval, 0.885-0.901] for the multifactor mixed-effects method and 2.122 cm [95% confidence interval, 2.108-2.136] for the single-factor methods; P<.0001 for both comparisons). The root mean squared errors of the multifactor methods were also better (lower) than those of the single-factor methods (1.126 cm [95% confidence interval, 1.118-1.133] for the machine learning [P<.0001] and 1.172 cm [95% confidence interval, 1.164-1.181] for the mixed-effects methods and 2.504 cm [95% confidence interval, 2.487-2.521] for the single-factor [P<.0001 for both comparisons]). The multifactor machine learning dilation models showed small but statistically significant improvements in accuracy compared to the mixed-effects regression models (P<.0001). The multifactor machine learning method produced a curve of descent with a mean absolute error of 0.512 cm (95% confidence interval, 0.509-0.515) and a root mean squared error of 0.660 cm (95% confidence interval, 0.655-0.666). External validation using independent data produced similar findings.
Cervical dilation models based on multiple clinically relevant parameters showed improved (lower) prediction errors compared to models based on time alone. The mean prediction errors were reduced by more than 50%. A more accurate assessment of departure from expected dilation and station may help clinicians optimize intrapartum management.

Normal labor and delivery are dependent on the presence of regular and effective contractions of the uterine myometrium. The mechanisms responsible for the initiation and maintenance of adequate and synchronized uterine activity that are necessary for labor and delivery result from a complex interplay of hormonal, mechanical, and electrical factors that have not yet been fully elucidated. Monitoring uterine activity during term labor and in suspected preterm labor is an important component of obstetrical care because cases of inadequate and excessive uterine activity can be associated with substantial maternal and neonatal morbidity and mortality. Inadequate labor progress is a common challenge encountered in intrapartum care, with labor dystocia being the most common indication for cesarean deliveries performed during labor. Hereafter, an accurate assessment of uterine activity during labor can assist in the management of protracted labor by diagnosing inadequate uterine activity and facilitating the titration of uterotonic medications before a trial of labor is prematurely terminated. Conversely, the ability to diagnose unwanted or excessive uterine activity is also critical in cases of threatened preterm labor, tachysystole, or patients undergoing a trial of labor after cesarean delivery. Knowledge of uterine activity in these cases may guide the use of tocolytic medications or raise suspicion of uterine rupture. Current diagnostic capabilities are less than optimal, hindering the medical management of term and preterm labor. Currently, different methods exist for evaluating uterine activity during labor, including manual palpation, external tocodynamometry, intrauterine pressure monitoring, and electrical uterine myometrial activity tracing. Legacy uterine monitoring techniques have advantages and limitations. External tocodynamometry is the most widespread tool in clinical use owing to its noninvasive nature and its ability to time contractions against the fetal heart rate monitor. However, it does not provide information regarding the strength of uterine contractions and is limited by signal loss with maternal movements. Conversely, the intrauterine pressure catheter quantifies the strength of uterine contractions; however, its use is limited by its invasiveness, risk for complications, and limited additive value in all but few clinical scenarios. New monitoring methods are being used, such as electrical uterine monitoring, which is noninvasive and does not require ruptured membranes. Electrical uterine monitoring has yet to be incorporated into common clinical practice because of lack of access to this technology, its high cost, and the need for appropriate training of clinical staff. Further work needs to be done to increase the accessibility and implementation of this technique by experts, and further research is needed to implement new practical and useful methods. This review describes current clinical tools for uterine activity assessment during labor and discusses their advantages and shortcomings. The review also summarizes current knowledge regarding novel technologies for monitoring uterine contractions that are not yet in widespread use, but are promising and could help improve our understanding of the physiology of labor, delivery, and preterm labor, and ultimately enhance patient care.

The past 20 years witnessed an invigoration of research on labor progression and a change of thinking regarding normal labor. New evidence is emerging, and more advanced statistical methods are applied to labor progression analyses. Given the wide variations in the onset of active labor and the pattern of labor progression, there is an emerging consensus that the definition of abnormal labor may not be related to an idealized or average labor curve. Alternative approaches to guide labor management have been proposed; for example, using an upper limit of a distribution of labor duration to define abnormally slow labor. Nonetheless, the methods of labor assessment are still primitive and subject to error; more objective measures and more advanced instruments are needed to identify the onset of active labor, monitor labor progression, and define when labor duration is associated with maternal/child risk. Cervical dilation alone may be insufficient to define active labor, and incorporating more physical and biochemical measures may improve accuracy of diagnosing active labor onset and progression. Because the association between duration of labor and perinatal outcomes is rather complex and influenced by various underlying and iatrogenic conditions, future research must carefully explore how to integrate statistical cut-points with clinical outcomes to reach a practical definition of labor abnormalities. Finally, research regarding the complex labor process may benefit from new approaches, such as machine learning technologies and artificial intelligence to improve the predictability of successful vaginal delivery with normal perinatal outcomes.

OBJECTIVE: To prove the potentialities of an integrated and sensorized childbirth platform as an innovative simulator for education of inexperienced gynecological and obstetrical medical students.
METHODS: A total of 152 inexperienced medical students were recruited to a simulation program on labor progression evaluation. After an introductory lecture on basic concepts of labor and birth given by an expert gynecologist, three different gynecologic scenarios were simulated using both a traditional obstetric simulator and the innovative proposed platform, for a total of six tests for each student. A score was assigned for each performed scenario, based on its correctness. Self-assessment questionnaires were compiled before and after the simulation program for additional subjective assessment.
RESULTS: Median score of the simulations performed with our platform was significantly higher than that of the simulations performed with a traditional simulator, for all the three experimented scenarios (P < 0.001).
CONCLUSIONS: The use of a sensorized platform for labor progression allowed for an accurate and faster diagnosis if compared with a traditional simulator even for inexperienced operators, supporting its use in clinical training, which could be realistically introduced into the clinical practice for medical student education.

BACKGROUND: One of the main reasons for the rising caesarean section rate is labor progression abnormalities. New guidelines were released promoting the changing paradigm from Friedman to Zhang\'s labor curves. However, the lack of evidence of its safety and the unclear effect on caesarean section rates have been challenging its adoption.
OBJECTIVE: Comparison between women with Friedman\'s criteria of arrested labor and women with Zhang\'s in terms of maternal and neonatal outcomes.
METHODS: Retrospective, single-center cohort study in a tertiary hospital between January 1st 2015 and December 31st of 2016.
METHODS: preterm or multiple deliveries, women without entering the active stage of labor, scheduled caesarean deliveries. Women were classified into 3 groups: normal progress, labor arrest by Friedman\'s criteria or by Zhang\'s criteria. Maternal morbidity included thrombotic, hemorrhagic, traumatic, infectious, and \"total\" (any of the previous morbidities). Adverse neonatal outcomes were assessed as a composite. Single and multivariable logistic regression was used to obtain the odd ratio (ORs) of each group and by stage of labor. Statistical significance threshold was set at 0,05.
RESULTS: From a total number of 5051 deliveries, 3665 deliveries were included in the study, 2839 with normal labor progression, 426 with labor arrest according to Friedman\'s criteria and 400 according to Zhang\'s criteria. Regarding neonatal outcomes, no significant differences were observed. Compared to normal labor, labor arrest was significantly associated with higher total maternal morbidity (OR for Friedman\'s criteria 3.04; 95% confidence interval, 2.26-4.09; OR for Zhang\'s criteria 3.59; 2.68-4.80), maternal hemorrhagic (OR for Friedman\'s criteria 2.87; 1.81-4.55; OR for Zhang\'s criteria 2.80; 1.75-4.49) and infectious morbidity (OR for Friedman\'s criteria 3.56; 2.44-5.18; OR for Zhang\'s criteria 4.77; 3.34-6.80). Results were still significant after adjustment for confounders. Comparing Friedman\'s and Zhang\'s criteria, no significant differences regarding maternal and neonatal outcomes were verified.
CONCLUSIONS: Changing criteria of labor arrest from Friedman\'s to Zhang\'s was not associated with more maternal morbidity in our study population nor worse neonatal outcomes. Changing labor arrest criteria from Friedman\'s to Zhang\'s may reduce caesarean section rates without an important increase in maternal and neonatal morbidities.

BACKGROUND: Childbirth experience is an increasingly recognized and important measure of quality of obstetric care. Previous research has shown that it can be affected by intrapartum care and how labor is followed. A partograph is recommended to follow labor progression by recording cervical dilation over time. There are currently different guidelines in use worldwide to follow labor progression. The two main ones are the partograph recommended by the World Health Organization (WHO) based on the work of Friedman and Philpott and a guideline based on Zhang\'s research. In our study we assessed the effect of adhering to Zhang\'s guideline or the WHO partograph on childbirth experience. Zhang\'s guideline describes expected normal labor progression based on data from contemporary obstetric populations, resulting in an exponential progression curve, compared with the linear WHO partograph. The choice of labor curve affects the intrapartum follow-up of women and this could potentially affect childbirth experience.
METHODS: The Labor Progression Study (LaPS) study was a prospective, cluster randomized controlled trial conducted at 14 birth centers in Norway. Birth centers were randomized to either follow Zhang\'s guideline or the WHO partograph. Nulliparous women in active labor, with one fetus in cephalic presentation at term and spontaneous labor onset were included. At 4 weeks postpartum, included women received an online login to complete the Childbirth Experience Questionnaire (CEQ). Total score on the CEQ, the four domain scores on the CEQ, and scores on the individual items on the CEQ were compared between the two groups.
RESULTS: There were 1855 women in the Zhang group and 1749 women in the WHO partograph group. There was no difference in the total or domain CEQ scores between the two groups. We found statistically significant differences for two individual items; women in the Zhang group scored lower on positive memories and feeling of control.
CONCLUSIONS: Based on our findings on childbirth experience there is no reason to prefer Zhang\'s guideline over the WHO partograph.

Laser vaporization of the cervix is an established method of treating cervical intra-epithelial neoplasia, but its effect on subsequent pregnancies remains controversial. The aim of this study was to investigate pregnancy outcomes after laser vaporization.
We conducted a retrospective study involving women who delivered live singletons between 2012 and 2019 in a tertiary hospital. The risks of adverse pregnancy outcomes after laser vaporization of the cervix were assessed using a multivariate regression model. The primary outcome was the adjusted odds ratio for preterm births. We also evaluated the course of labor progression, duration of labor, risk of emergency cesarean deliveries, and the risk of cervical laceration as secondary outcomes.
In total, 3359 women were analyzed in this study. The risk of preterm birth was significantly higher in pregnancies after laser vaporization of the cervix (adjusted odds ratio [AOR] 1.84, 95% confidence interval [95% CI] 1.06-3.20; p = 0.030). The duration of the first stage of labor was significantly shorter in the post-treatment group (median 255 min vs. 355 min; p = 0.0049). We did not observe significant differences in the duration of the second stage of labor (median 21 min vs 20 min; p = 0.507) or the rates of other obstetric events, including emergency cesarean deliveries (AOR 0.736; 95% CI 0.36-1.50; p = 0.400) and cervical laceration (AOR 0.717; 95% CI 0.22-2.35; p = 0.582).
Laser vaporization of the cervix is associated with an increased risk of preterm births and a shorter duration of the first stage of labor in subsequent pregnancies. Careful consideration is necessary when selecting a method of treatment for the uterine cervix of patients wishing future pregnancies.

Objectives Short interpregnancy intervals (IPI) have been linked to multiple adverse maternal and neonatal outcomes, but less is known about prolonged IPI, including its relationship with labor progression. The objective of the study was to investigate whether prolonged IPIs are associated with longer second stages of labor. Methods A perinatal database from Kaiser Permanente Hawaii was used to identify 442 women with a prolonged IPI ≥60 months. Four hundred forty two nulliparous and 442 multiparous women with an IPI 18-59 months were selected as comparison groups. The primary outcome was second stage of labor duration. Perinatal outcomes were compared between these groups. Results The median (IQR) second stage of labor duration was 76 (38-141) min in nulliparous women, 15 (9-28) min in multiparous women, and 18 (10-38) min in women with a prolonged IPI (p<0.0001). Pairwise comparisons revealed significantly different second stage duration in the nulliparous group compared to both the multiparous and prolonged IPI groups, but no difference between the multiparous and prolonged IPI groups. There was a significant association with the length of the IPI; median duration 30 (12-61) min for IPI ≥120 months vs. 15 (9-27) min for IPI 18-59 months and 16 (9-31) min for IPI 60-119 months (p=0.0014). Conclusions The second stage of labor did not differ in women with a prolonged IPI compared to normal multiparous women. Women with an IPI ≥120 months had a significantly longer second stage vs. those with a shorter IPI. These findings provide a better understanding of labor progression in pregnancies with a prolonged IPI.

Normal labor curves have not been assessed for women undergoing a trial of labor after cesarean delivery (TOLAC). This study examined labor patterns during TOLAC in relation to epidural analgesia use.
Retrospective cohort study of deliveries of women undergoing TOLAC at a single, academic, tertiary medical center. Length of first, second and third stages of labor was compared between 424 women undergoing TOLAC in the current labor with no previous vaginal delivery (VD) and 357 women with at least one previous VD and current TOLAC.
Women in the TOLAC only group had significantly longer labors compared to women in the previous VD and TOLAC group. In both groups, women who underwent epidural analgesia had longer first and second stages of labor. In the TOLAC only group, more women who had epidural analgesia tended to deliver vaginally as compared to those who did not (P = 0.09). For women who delivered vaginally, the 95th percentile for the second stage duration with epidural was 3.40 h in the TOLAC only group and 2.3 h in the previous VD and TOLAC group. The 95th percentile for the second stage duration without epidural was 1.4 h in the TOLAC only group and 0.9 h in the previous VD and TOLAC group.
Operative intervention (instrumental delivery/cesarean delivery (CD)) might be considered for women attempting TOLAC after a 2-h duration of second stage without epidural and 3-h duration with epidural, with an hour less for women who also had previous VD.