Predictive value of cervimetric labour patterns in primigravidae

Labor curves based on cervical dilatation over time and their accuracy and effectiveness: A systematic scoping review

OBJECTIVES

This systematic scoping review was conducted to 1) identify and describe labor curves that illustrate cervical dilatation over time; 2) map any evidence for, as well as outcomes used to evaluate the accuracy and effectiveness of the curves; and 3) identify areas in research that require further investigation.

METHODS

A three-step systematic literature search was conducted for publications up to May 2023. We searched the Medline, Maternity & Infant Care, Embase, Cochrane Library, Epistemonikos, CINAHL, Scopus, and African Index Medicus databases for studies describing labor curves, assessing their effectiveness in improving birth outcomes, or assessing their accuracy as screening or diagnostic tools. Original research articles and systematic reviews were included. We excluded studies investigating adverse birth outcomes retrospectively, and those investigating the effect of analgesia-related interventions on labor progression. Study eligibility was assessed, and data were extracted from included studies using a piloted charting form. The findings are presented according to descriptive summaries created for the included studies.

RESULTS AND IMPLICATIONS FOR RESEARCH

Of 26,073 potentially eligible studies, 108 studies were included. Seventy-three studies described labor curves, of which ten of the thirteen largest were based mainly on the United States Consortium on Safe Labor cohort. Labor curve endpoints were 10 cm cervical dilatation in 69 studies and vaginal birth in 4 studies. Labor curve accuracy was assessed in 26 studies, of which all 15 published after 1986 were from low- and middle-income countries. Recent studies of labor curve accuracy in high-income countries are lacking. The effectiveness of labor curves was assessed in 13 studies, which failed to prove the superiority of any curve. Patient-reported health and well-being is an underrepresented outcome in evaluations of labor curves. The usefulness of labor curves is still a matter of debate, as studies have failed to prove their accuracy or effectiveness.

The sonopartogram

The assessment of labor progress from digital vaginal examination has remained largely unchanged for at least a century, despite the current major advances in maternal and perinatal care. Although inconsistently reproducible, the findings from digital vaginal examination are customarily plotted manually on a partogram, which is composed of a graphical representation of labor, together with maternal and fetal observations. The partogram has been developed to aid recognition of failure to labor progress and guide management-specific obstetrical intervention. In the last decade, the use of ultrasound in the delivery room has increased with the advent of more powerful, portable ultrasound machines that have become more readily available for use. Although ultrasound in intrapartum practice is predominantly used for acute management, an ultrasound-based partogram, a sonopartogram, might represent an objective tool for the graphical representation of labor. Demonstrating greater accuracy for fetal head position and more objectivity in the assessment of fetal head station, it could be considered complementary to traditional clinical assessment. The development of the sonopartogram concept would require further undertaking of serial measurements. Advocates of ultrasound will concede that its use has yet to demonstrate a difference in obstetrical and neonatal morbidity in the context of the management of labor and delivery. Taking a step beyond the descriptive graphical representation of labor progress is the question of whether a specific combination of clinical and demographic parameters might be used to inform knowledge of labor outcomes. Intrapartum cesarean deliveries and deliveries assisted by forceps and vacuum are all associated with a heightened risk of maternal and perinatal adverse outcomes. Although these outcomes cannot be precisely predicted, many known risk factors exist. Malposition and high station of the fetal head, short maternal stature, and other factors, such as caput succedaneum, are all implicated in operative delivery; however, the contribution of individual parameters based on clinical and ultrasound assessments has not been quantified. Individualized risk prediction models, including maternal characteristics and ultrasound findings, are increasingly used in women's health-for example, in preeclampsia or trisomy screening. Similarly, intrapartum cesarean delivery models have been developed with good prognostic ability in specifically selected populations. For intrapartum ultrasound to be of prognostic value, robust, externally validated prediction models for labor outcome would inform delivery management and allow shared decision-making with parents.

Randomized controlled trial of labor outcomes with action line placement at 2 hours versus 4 hours on the partograph

OBJECTIVE

To evaluate whether treatment of slow labor progress among term nulliparous women using a 2-hour partograph action line reduces the incidence of prolonged labor versus a 4-hour action line.

METHODS

Randomized controlled trial of nulliparous women with a term singleton, non-macrosomic, cephalic fetus in labor attending a university hospital in Nigeria (2008-2015). For labor supervision, women were randomly assigned to the 2-hour (n=320) or 4-hour (n=320) partograph action line group. slow labor progress was treated with oxytocin augmentation The primary outcome was incidence of prolonged labor (>12 hours). Delivery mode, neonatal outcomes, and maternal satisfaction with treatment were secondary outcomes.

RESULTS

Prolonged labor rate did not significantly differ between the 2-hour (7/320, 2.2%) and 4-hour (8/320, 2.5%) action line groups. Secondary outcomes did not differ significantly. Oxytocin augmentation to treat slow labor progress was needed for 87 (27.2%) and 61 (19.1%) women in the respective 2- and 4-hour groups (P=0.025). Mean duration of first and second labor stages differed significantly between the groups (P<0.05).

CONCLUSION

The 2-hour partograph action line did not reduce incidence of prolonged labor relative to the 4-hour action line. Partograph with a 4-hour action line is recommended for labor supervision in all facilities.

CLINICAL TRIAL REGISTRATION

Registered at ClinicalTrials.gov as (https://clinicaltrialsgov/show/NCT02911272).

Estimating time to full uterine cervical dilation using genetic algorithm

The objectives of this study were to provide new parameters to better understand labor curves, and to provide a model to predict the time to full cervical dilation (CD). We studied labor curves using the retrospective records of 594 nulliparas, including at term, spontaneous labor onset, and singleton vertex deliveries of normal birth weight infants. We redefined the parameters of Friedman's labor curve, and applied a three-parameter model to the labor curve with a logistic model using the genetic algorithm and the Newton-Raphson method to predict the time necessary to reach full CD. The genetic algorithm is more effective than the Newton-Raphson method for modeling labor progress, as demonstrated by its higher accuracy in predicting the time to reach full CD. In addition, we predicted the time (11.4 hours) to reach full CD using the logistic labor curve using the mean parameters (the power of CD = 0.97 cm/hours, a midpoint of the active phase = 7.60 hours, and the initial CD = 2.11 cm). Our new parameters and model can predict the time to reach full CD, which can aid in the forecasting of prolonged labor and the timing of interventions, with the end goal being normal vaginal birth.

A Randomized Controlled Trial of a Bedside Partogram in the Active Management of Primiparous Labour

OBJECTIVE

The partogram is a pictorial representation of the progress of labour, used in an effort to enhance early recognition of dystocia and help avoid Caesarean section (CS). The objective of this study was to evaluate the effect of partogram use on the CS and obstetric intervention rates.

METHODS

We conducted a randomized controlled trial of use of the partogram in 1932 primiparous women with uncomplicated pregnancies at term. Patients were randomly assigned to one of two groups: the standard group, who had the progress of labour charted in written notes, or the partogram group, whose progress in labour was recorded using a bedside graphical partogram as well as in written notes. Outcomes were stratified according to whether labour was spontaneous or induced and whether membranes were initially intact or ruptured. The primary outcome was the rate of CS; secondary outcome measures were rates of obstetric intervention for dystocia.

RESULTS

There was no significant difference between the groups in rates of CS (partogram 24%, standard notes 25%), rates of other interventions, amniotomy, oxytocin use, or the mean cervical dilatation in labour.

CONCLUSION

In this study, the use of a partogram without a mandatory management of labour protocol had no effect on rates of CS or other intrapartum interventions in healthy primiparous women at term.

Comparative study of induction of labor in nulliparous women with premature rupture of membranes at term compared to those with intact membranes: Duration of labor and mode of delivery

AIM

To evaluate the effect of premature rupture of membranes (PROM) at term on the duration of labor and mode of delivery in comparison with intact membranes in nulliparous women with an unfavorable cervix whose labor was induced.

METHODS

This retrospective cohort study included all term nulliparous women with an unfavorable cervix requiring labor induction over a 2-year period. Prostaglandin E(2) (dinoprostone) and oxytocin were used for labor induction. Criteria for enrolment included (i) singleton pregnancy; (ii) term nulliparous women; or (iii) Bishop score below 6. Statistics were analyzed with Student's t-test, chi(2)-test, Fisher's exact test, and multiple logistic regression.

RESULTS

Our study subjects were 82 women whose labor was induced for PROM and 219 women with intact membranes whose labor was induced for social or fetal reasons. The mean durations of active phase of labor were not significantly different between women with PROM and those with intact membranes. However, the women with PROM had a significantly longer mean duration of second stage and a higher rate of cesarean delivery for failure to progress than those with intact membranes. Multiple logistic regression demonstrated that only PROM and fetal macrosomia were significantly associated with an increased risk of cesarean delivery for failure to progress after other confounding variables were adjusted.

CONCLUSIONS

Labor induction for PROM at term in nulliparous women with an unfavorable cervix is associated with longer duration of the second stage and a higher risk of cesarean delivery for failure to progress in comparison to those with intact membranes.

Obstetric risk factors for failure to progress in the first versus the second stage of labor

OBJECTIVE

To compare obstetric risk factors for failure of labor to progress in the first versus the second stage.

STUDY DESIGN

A comparison was performed of all singleton, vertex and term deliveries with an unscarred uterus, complicated with non-progressive labor during the first and the second stages. Deliveries occurred between the years 1988 and 1999 in a tertiary university medical center.

RESULTS

Patients with non-progressive labor in the first stage (n = 1197) were significantly older, of higher birth order, and were more likely to have complications such as gestational diabetes, hypertensive disorders, premature rupture of membranes, meconium-stained amniotic fluid, hydramnios and oligohydramnios (p < 0.001 for all variables) as compared to patients with non-progressive labor in the second stage (n = 1545). In addition, pregnancies complicated with non-progressive labor in the first stage had a significantly higher rate of fetal macrosomia as compared to patients with non-progressive labor in the second stage (11.6% vs. 8.8%; p < 0.001).

CONCLUSIONS

Higher rates of fetal macrosomia and high-risk pregnancies were noted among pregnancies complicated with non-progressive labor during the first vs. the second stage. The significant increase in Cesarean deliveries during the first stage of labor among high-risk pregnancies might reflect exaggerated concern of caregivers. This concern may influence an overall conservative attitude leading to the seemingly simpler mode of direct intervention by Cesarean delivery.

Risk factors for arrest of descent during the second stage of labor

OBJECTIVE

To define obstetrical risk factors for arrest of descent during the second stage of labor and to determine perinatal outcome.

STUDY DESIGN

All singleton, vertex, term deliveries with an unscarred uterus, between the years 1988 and 1999 were included. Univariable and multivariable analysis were performed to investigate independent risk factors associated with arrest of descent during the second stage of labor and the perinatal outcome.

RESULTS

The study included 93266 deliveries, of these 1545 (1.7%) were complicated with arrest of descent during the second stage of labor. Using a multivariable analysis, the following obstetric risk factors were found to be significantly associated with arrest of descent: nulliparity (OR=7.8, 95% CI=6.9-8.7; P<0.001), birth weight >4 kg (OR=2.3, 95% CI=1.9-2.8; P<0.001), epidural analgesia (OR=1.8, 95% CI=1.6-2.0; P<0.001), hydramnios (OR=1.6, 95% CI=1.3-2.0; P<0.001), hypertensive disorders (OR=1.5, 95% CI=1.3-1.8; P<0.001), gestational diabetes A1 and A2 (OR=1.5, 95% CI=1.2-1.8; P<0.001), male gender (OR=1.4, 95% CI=1.2-1.5; P<0.001), premature rupture of membranes (PROM, OR=1.3, 95% CI=1.04-1.6; P=0.021), and induction of labor (OR=1.2, 95% CI=1.02-1.4; P=0.030). Deliveries complicated by arrest of descent resulted in cesarean section in 20.6%, vacuum extraction in 74.0%, and forceps delivery in 5.4%. Newborns delivered after arrest of descent during the second stage of labor had significantly higher rates of low Apgar scores (<7) at 1 and 5 min, as compared to the controls (12.7 vs. 2.1%, P<0.001; and 0.9 vs. 0.2%, P<0.001, respectively). Nevertheless, no significant differences were noted between the groups regarding perinatal mortality (0.38 vs. 0.44%; P=0.759).

CONCLUSIONS

Major risk factors for arrest of descent during the second stage of labor were nulliparity, fetal macrosomia, epidural analgesia, hydramnios, hypertensive disorders and gestational diabetes mellitus. These risk factors should be carefully evaluated during pregnancy in order to actively manage high-risk pregnancies.

Prediction of vaginal delivery following caesarean section for failure to progress based on the initial aberrant labour pattern

OBJECTIVE

To determine whether the pattern of cervical dilatation prior to caesarean section for 'failure to progress' can predict the outcome of subsequent labour.

STUDY DESIGN

Single hospital case note review of 171 women delivered by caesarean section for failure to progress and subsequently delivering at the same hospital. Cervicograms were categorized into one of the four patterns by an assessor blinded to the subsequent outcome. Statistical analysis was done by analysis of variance.

RESULTS

The incidence of vaginal delivery did not significantly differ between the groups.

CONCLUSION

Categorisation of failure to progress by partographic abnormality does not predict subsequent successful vaginal delivery.

Visual effect of partogram designs on the management and outcome of labour

A prospective study of 3 partogram designs was performed in 990 women in labour with singleton pregnancy. Partogram A, B and C showed a progressively flatter steepness of the curve of labour progression. Oxytocin was administered in 35.1% of partogram-A users, 45.9% of partogram-B users (p = 0.001) and 44.1% of partogram-C users (p = 0.035). Significantly fewer patients among the partogram-A users (10.2%) were administered oxytocin too early compared to 18.6% of partogram-B users and 20.5% of partogram-C users. Of those with spontaneous onset of labour, a significantly smaller total dose of oxytocin was administered to the partogram-A users compared to the other 2 groups. Ominous electrocardiotocographic fetal heart patterns were detected less frequently during the first stage of labour in partogram A users (0.4%) compare to partogram-B users (1.1%) and partogram-C users (3.0%). Significantly fewer infants born to partogram-A users had depressed Apgar scores at 1 and 5 minutes. Partograms displaying a flat graph, compared to a steep graph, were more often considered to have a slow progress of labour. Adoption of partograms showing a steep graph of progress of cervical dilatation is recommended.

Using the medical audit cycle to reduce cesarean section rates

OBJECTIVE

Our purpose was to determine whether completion of the medical audit cycle in labor ward practice could safely reduce cesarean section rates.

STUDY DESIGN

A retrospective medical audit of all deliveries from 1984 to 1988 was performed. The groups of women contributing most to the overall cesarean section rate were identified. Strategies for labor management directed at the primary indication for cesarean section (dystocia) were developed and introduced. The effect was monitored prospectively from 1989 through 1992. Data were analyzed with the chi 2 test.

RESULTS

A total of 21,125 deliveries were studied. After management change the overall cesarean section rate was decreased (9.5% vs 12%, p < 0.0001). In our population spontaneously laboring nulliparous women with a singleton, cephalic, term pregnancy contributed a significant number of cesarean sections 1982 to 1988 (19.7% of all cesarean sections). Applying principles of early diagnosis and treatment of dystocia in these women resulted in a decrease in the cesarean section rate (2.4% vs 7.5%, p < 0.0001). This was primarily responsible for the overall decrease in the cesarean section rate.

CONCLUSION

Effective medical audit of labor management can reduce cesarean section rates.

Nulliparous caesarean section in the home of active management of labour

The world-wide incidence of Caesarean section continues to rise with dystocia recognized as the major indication. Active management of labour has been proposed as an alternative treatment to Caesarean section for dystocia. At the National Maternity Hospital, Dublin, a recent increase in the Caesarean section rate has been observed. This retrospective review reveals this to be due to other indications.

The contribution of dystocia to the cesarean section rate

OBJECTIVE

Our purpose was to examine the indications for performing cesarean sections in current obstetric practice and to define and measure the true contribution of dystocia ("difficult labor") to the overall cesarean section rate.

STUDY DESIGN

A prospective audit was done of all cesarean sections performed during 1991 at The Queen Mother's Hospital, Glasgow, a teaching hospital and tertiary referral center.

RESULTS

The cesarean section rate for 1991 was 16.3%. Dystocia was the primary indication in 16% of all cesarean sections in 1991 but was actually a contributing factor, directly or indirectly, in the decision to operate in up to 38% of all cesarean sections that year. Seventy-eight percent of patients delivered because of dystocia were in spontaneous labor. We advocate more widespread use of a policy of active management in nulliparous women who labor spontaneously. If dystocia is addressed successfully, then many repeat cesarean sections may also be avoided.

CONCLUSIONS

Improved management of dystocia in nulliparous women, such as the use of a policy of active management of labor, may be the most useful approach to reducing the cesarean section rate in modern obstetric practice.

Cervical contractions: the response of the cervix to oxytocic stimulation in the latent phase of labour

OBJECTIVE

To assess the cervical response to myometrial activity in early labour.

DESIGN

Prospective observational study.

SUBJECTS

Women requiring oxytocin stimulation in induced and spontaneous labours.

SETTING

A teaching hospital in Birmingham.

MAIN OUTCOME MEASURES

Simultaneous comparison of the cervical response to myometrial contractions was made on a cycle by cycle basis to deduce the properties of the cervix in early labour.

RESULTS

Sixty-seven patients have been monitored, of whom 63 had satisfactory cervimetry data. Thirty (47.6%) women exhibited cervical contractions in response to myometrial activity. This response was only observed at dilatations up to 4 cm. The change in behaviour coincides with the transition from latent to active phases of dilatation. The length of the latent phase of labour was significantly longer in those women who exhibited cervical contractions (P < 0.001), although the active phase was similar in the two groups (P > 0.1). The group without cervical contractions exhibited a greater degree of effacement (P < 0.05) and tended to have more dilated cervices (P < 0.01) than those who showed cervical contractions.

CONCLUSIONS

It is possible for the cervix to contract in early labour. This response may be the result of incomplete preparation of the cervix for the process of dilatation, and is seen during what is recognised as the latent phase in those women in whom the cervix is unaffected and undilated. These properties of the cervix may explain the poor results obtained from oxytocin stimulation of labour in the latent phase.

Measurement of uterine activity in labour--clinical aspects

Intra-uterine pressure measurement remains the most objective way of measuring uterine activity in labour, and in this respect is superior to clinical assessment or external tocography. However there is little evidence to show that improving the assessment of uterine activity in labour is associated with an improvement in the outcome of labour for mother or fetus. It seems logical that use of intra-uterine pressure monitoring will provide additional safety in women with a scarred uterus, breech presentation, high parity, or apparent failure of response to induction or augmentation of labour with the usual dose rates of oxytocics, but this has not been established by appropriately sized clinical trials. Further research to establish the role of uterine activity measurement in labour is urgently needed.

What cervical dilatation rate during active labour should be considered abnormal?

The present study tested the common notion of slow labour that only dilatation rates of 1 cm/h and above lead to normal (intervention free) delivery. We examined all primiparous spontaneous term labours cared for in our hospital over a 1 year period when a protocol for intervention in the case of slow dilation rate was not in place. Of 505 consecutive singleton labours, 105 (20.6%) progressed at an overall cervical dilatation rate of less than 1 cm/h. However, only those progressing at 0.5 cm/h and less (n = 52 or 10.3% of the total) had significantly increased rates of oxytocin usage and of caesarean section. The data suggest that there may be a more conservative definition of slow labour.

Does oxytocin augmentation increase perinatal risk in primigravid labor?

To assess the influence of high-dose oxytocin augmentation of spontaneous labor, a consecutive series of 30,874 primigravid term deliveries were analyzed for adverse perinatal outcome. In spite of a longer mean duration of labor, the frequencies of asphyxial perinatal death, neonatal seizures, and abnormal neonatal neurologic behavior were not significantly increased in 14,119 (45%) oxytocin-treated patients. There was no case of uterine rupture in any primigravid labor during the study. These results from 13 years of clinical practice provide reassurance about maternal and fetal safety if oxytocin is used as part of a protocol of active management to correct dystocia when spontaneous primigravid labor with vertex presentation fails to progress.

The fetal maturity and mode of delivery of a woman's first baby influences the characteristics of her next labour

There are well documented differences between the characteristics of labour in primigravidae and multigravidae. The present study was undertaken to determine whether the gestational age and mode of delivery of a woman's first baby influences the characteristics of labour in her next pregnancy. Information regarding previous obstetric history and subsequent obstetric performance was derived from a database of 75,974 consecutive singleton births. As a group, women with a history of one preterm vaginal delivery had labour characteristics similar to those women whose one previous pregnancy had resulted in a vaginal delivery at term. When this group were analysed by the gestation at which the previous birth had occurred, a gestation-dependent effect was seen. Women whose first birth had been at less than 28 weeks gestation behaved in a similar manner to primiparous women. On the other hand, the characteristics of labour in women whose first birth had occurred between 33 and 36 weeks gestation were similar to those of women who had had a previous vaginal delivery at term. Women whose first delivery had been by caesarean section behaved in a similar manner to primiparae. The typical differences between the characteristics of first and second labours are the result of a gradual change which appears to be related to the gestation at which the first birth occurred.

Assessment of cervical dilatation during labor: a review

Various techniques for assessment of cervical dilatation during labor or 'cervimetry' have been described, including digital, (electro)mechanical, electromagnetic and ultrasound cervimetry. In this paper the validity and usefulness of instrumental cervimetry is assessed on the basis of the available literature. Cervimetry using ultrasound transducers allows continuous and reliable recording of cervical dilatation during labor with little discomfort to the patient. In comparison with other instrumental techniques for measurement of cervical dilation ultrasound cervimetry seems to be the most promising method available.

Uterine activity in dysfunctional labour and target uterine activity to be aimed with oxytocin titration

Uterine activity was quantified using a transducer tipped intrauterine catheter in 75 nulliparous women with dysfunctional labour. The active contraction area profiles in these women were below the median levels reported for those who had normal progress of labour from our institution. When uterine activity was augmented with oxytocin, 90.7% progressed in labour and delivered vaginally. Six patients (8%) showed poor progress despite good uterine activity and had to be delivered by caesarean section (CS) for failure to progress and signs of cephalopelvic disproportion. The pre- and post-augmentation uterine activity were similar in those who delivered vaginally or by CS and was not helpful in identifying those who had cephalopelvic disproportion. Of the 75 women who had slow progress of labour, 50 had a contraction frequency of less than 1 in 3 min whilst 25 had a minimum frequency of 1 in 3 min or more. All except one in the latter group delivered vaginally when oxytocin was titrated to achieve a contraction frequency of 1 in 2 to 2 1/2 min which were clinically judged to be adequate based on a duration greater than 40 sec. Oxytocin should be titrated to achieve a target contraction frequency of 1 in 2 to 2 1/2 min lasting greater than 40 sec to achieve good obstetric outcome in those with dysfunctional labour.

The endocrinology of parturition in the human

Current evidence suggests that oestrogens, progesterone, relaxin, the prostaglandins, and oxytocin are all hormones concerned to a major degree with the onset and maintenance of parturition. Oestrogens, relaxin, and the prostaglandins are particularly involved with cervical ripening, while prostaglandins, progesterone and oxytocin are more involved in regulating myometrial contractility. Catecholamines may also have some regulatory function in relation to uterine contractions. Progesterone dominance during pregnancy is associated with a firm closed cervix, few myometrial gap junctions, low calcium levels in the cells, and a quiescent myometrium. At term, a change in the oestrogen/progesterone balance favours cervical ripening and increased uterine activity. Of particular importance at the level of the muscle cell are changes in the number of oxytocin receptors; a complex interaction between cAMP and phosphoinositide metabolism governs the intracellular level of calcium, thus regulating contractile activity.

A model for the generation of intra-uterine pressure in the human parturient uterus which demonstrates the critical role of the cervix

A mathematical model is presented which describes the relationship between intrauterine pressure and uterine wall tension. Wall tension is evaluated in terms of muscular contraction in an active myometrium and the modulating effect of a passive, compliant cervix. Using a computer programme which simulates the recruitment of contractile elements in the uterine wall, it is possible to generate theoretical pressure waveforms. The effects on these waveforms produced by changing cervical properties are demonstrated and compared with observed phenomena. The physiological and clinical implications are evaluated.

An application of the Markov process for quantitative prediction of labor progress

To quantitatively predict the progress of labor, we devised a mathematical model suitable for the Markov process. Included were 625 primiparas who went into spontaneous labor between 37 and 41 weeks of gestation with a cephalic presentation. When applying the Markov process, the sequence of labor was divided into eight categories from 4 cm cervical dilatation to delivery of the baby. Based on all data collected, a transition matrix was calculated, using a microcomputer system, in which the value in each element showed the percent of probability of progression in labor from one given state to another over a 30-minute period. This matrix was found to be available for evaluating the course of labor in clinical practise with a good predictive value and therefore the Markov process could be confirmed to be actually applicable as an analytical model.

Augmentation of labour--mode of delivery related to cervimetric progress

This study was designed to investigate the possible benefits, in terms of obstetric and neonatal outcome, of a prolonged augmentation period with oxytocin in patients with dysfunctional first stage of labour. The majority of patients (65.5% of nulliparas and 83.8% of multiparas) responded with satisfactory progress within the first 4 hours of augmentation and the Caesarean section rate was low in this group (1.3%). In those with unsatisfactory progress during the first 4 hours of augmentation a further 4 hour period of augmentation resulted in vaginal delivery for 50.7% of nulliparas with primary dysfunctional labour and 33.3% of those with secondary arrest in labour. Corresponding figures for multiparas were 41.7% and 25.0%, respectively. The neonatal outcome was uniformly good. It is concluded that the management protocol presented for augmentation of labour seems to be a safe procedure and might reduce the rising Caesarean section rate for dystocia.

A randomized control study of oxytocin augmentation of labour. 2. Uterine activity

Uterine activity was measured in 60 women whose first labour was progressing slowly in the active phase. The mean level of active contraction area (uterine activity integral, UAI) before oxytocin augmentation was 898 (SD 458) kPas/15 min. UAI increased significantly with time, even in women not given oxytocin. UAI increased logarithmically with increasing oxytocin infusion rate. Levels of uterine activity before and after oxytocin infusion are correlated positively such that the higher the initial level of UAI the higher the UAI in response to oxytocin. However, the regression line approaches the line of identity such that even with high doses of oxytocin UAI would not be likely to exceed 2500 kPas/15 min. There is a positive correlation between uterine activity and cervical dilatation rate in unstimulated labour; however, this is less evident following oxytocin infusion. Increases in uterine activity below 1200 kPas/15 min result from both higher frequency and active pressure, whereas above 1200 kPas/15 min any increase is due mainly to a rise in frequency.

A randomized control study of oxytocin augmentation of labour. 1. Obstetric outcome

Sixty women who were progressing slowly in spontaneous labour were assigned at random to three management protocols. Group 1 were observed without the use of oxytocin for 8 h while groups 2 and 3 were managed with a low-dose and high-dose oxytocin protocol respectively. The caesarean section rates were not significantly different between the three groups: 45%, 35% and 26% respectively. Cervical dilatation rate increased significantly after oxytocin infusion in both treatment groups compared with controls. The 'delay-to-delivery' interval and second stage duration were significantly shorter in the high-dose group than in the control group. There were no measurable differences in the condition of the newborn infants between the three groups.

Estimating the probability of spontaneous delivery conditional on time spent in the second stage

The duration of second stage labour was studied, retrospectively, among 410 primigravidas who received epidural analgesia in the first stage of spontaneous labour at term (greater than 37 weeks). Survival analysis was used to investigate how the likelihood of a spontaneous delivery was related to time spent in the second stage, and how some maternal and fetal factors influenced this relationship. The proportion of spontaneous deliveries that had occurred by any given time was greatly influenced by maternal age and infant birthweight. However, the women who were least likely to have been delivered by any given time after full dilatation, were also the ones who were least likely to be delivered within any given subsequent time interval. If delivery had not occurred by 3 h, the probability that it would take place in the next 3 h was well under 30% in most cases. We conclude that second stage labour in excess of 3 h is likely to be beneficial only if certain criteria, which are defined in the paper, are met.

The effect of oxytocin infusion on uterine activity levels in slow labour

Uterine activity was studied in 31 women who were progressing slowly in spontaneous labour. In 75%, levels of uterine activity were below the tenth centile for normal spontaneous labour (mean uterine activity integral, UAI, 593 kPas/15 min; SD 296). Following oxytocin infusion, there was a significant increase in uterine activity to a mean of 1124 kPas/15 min (SD 276), which was the same as in normal spontaneous labour. The response to oxytocin was dependent upon the pre-existing level of uterine activity, and sensitivity to oxytocin, rather than the dose rate; 84% responded to infusion rates of less than 8 mU/min. The response to oxytocin was best expressed in terms of active contraction area (uterine activity integral, UAI) or Montevideo units, rather than the frequency or active pressure of contractions. The rate of cervical dilatation following oxytocin augmentation could not be predicted either by the increase in uterine activity or by the actual level of activity achieved.

Management of spontaneous rupture of the membranes in the absence of labor in primigravid women at term

One hundred and thirty-five healthy primigravid women at or near term with spontaneous rupture of the membranes without uterine contractions were submitted to a prospective trial of management. Rupture of the membranes was diagnosed by speculum examination. If labor did not commence, induction was performed by oxytocin infusion starting at 9 AM following admission. One hundred and five women went into labor spontaneously before induction became necessary. Sixty-three of these women required augmentation with oxytocin. Twenty-seven percent of the induced group required cesarean section delivery compared to 10% of those in spontaneous labor augmented by oxytocin and to none of those who did not require oxytocin (p less than 0.01). Ninety-four percent of those in spontaneous labor were delivered vaginally compared to 73% of the induced group (p less than 0.01). Forty-one percent of the augmented group were delivered by forceps. Awaiting the spontaneous onset of labor for 24 hours or less did not result in clinical maternal or neonatal infection. We would therefore advocate awaiting the spontaneous onset of labor after spontaneous rupture of membranes without contractions at or near term in healthy primigravid women for up to 24 hours because it seems to confer significant advantages without producing any additional hazard.

Obstetric characteristics in different racial groups

A detailed analysis of 2632 consecutive pregnancies in white, black and Asian women, who were delivered during the period 1978 to 1980, found significant differences between the three ethnic groups. Asian primiparae had the longest first and second stages of labour, with the highest incidence of prolonged latent phase (14%) and primary dysfunctional labour (30%). Black primiparae and multiparae had the highest incidence of secondary arrest in the first stage of labour (10% and 4% respectively) and of primary dysfunctional labour, with the greatest recourse to emergency caesarean section (13% and 4% respectively). The mean birthweight for singletons born between 37 and 42 weeks was 3.37 kg for white babies, 3.25 kg for black babies and 3.14 kg for Asian babies. There was no racial difference in perinatal mortality or morbidity in this survey.

Controlled study comparing vaginal prostaglandin E2 pessaries with intravenous oxytocin for the stimulation of labour after spontaneous rupture of the membranes

In a prospective randomized study, 36 patients with spontaneous rupture of the membranes of greater than or equal to 4 h duration were stimulated with 3 mg vaginal prostaglandin E2 pessaries or intravenous oxytocin. Oxytocin stimulation was associated with shorter labours and a lower incidence of abnormal cervimetric progress. Of the patients given prostaglandin pessaries, 40% required a second dose after 4 h for slow progress; 45% of the primigravidae subsequently developed abnormal labour which was corrected by augmentation with oxytocin in all cases. One caesarean section was carried out for disproportion, and the remaining 35 patients were delivered vaginally. Prostaglandin pessaries were not associated with an increased incidence of hyperstimulation or sepsis. In conclusion, although PGE2 pessaries are safe in spontaneous rupture of the membranes, intravenous oxytocin is more efficient in stimulating labour.

Should we abandon Kielland's forceps?

To assess the risks associated with the use of Kielland's forceps 2708 consecutive deliveries were studied prospectively and the neonatal outcome related to the mode of delivery. Of the 1191 primigravidas, 279 (23.4%) underwent instrumental delivery, of whom 65 (5.5%) were delivered with Kielland's forceps. There was no difference in early neonatal outcome (as judged by Apgar scores, intubations, and admission to the special care baby unit) between these babies and those delivered normally or by non-rotational forceps, but a higher proportion of the 127 (10.7%) delivered by emergency caesarean section were compromised. Of the 1517 multigravid patients, only 57 (3.8%) underwent instrumental delivery, 15 (1.0%) by Kielland's forceps. Among these babies, also, the outcome was no worse than for those delivered normally, but the babies delivered by caesarean section showed a greatly increased incidence of low Apgar scores, intubations, and admission to the special care baby unit. There were no stillbirths or neonatal deaths among babies delivered by Kielland's forceps, nor were there any cases of severe birth trauma or of obvious neonatal morbidity.