Tocolysis with advanced cervical dilatation

Relationship between cervical dilation and time to delivery in women with preterm labor

Background:

Early recognition of the signs and symptoms of preterm labor (PTL) is important in order to establish treatment. Our aim was to determine the relation between cervical dilatation and time interval from admission to delivery in women with preterm labor.

Materials and Methods:

A retrospective cohort study was conducted on 83 singleton gestations admitted for preterm labor between 24 weeks and 34 weeks, who subsequently delivered preterm. Women were categorized into three groups of cervical dilatation (0-2 cm, 3-6 cm, >6 cm) and the time interval from admission to delivery was compared. Cox regression analysis was performed to assess the association between cervical dilatation and time interval from admission to delivery. The other variables examined were gestational age (GA) at admission and length of the cervix, when performed.

Results:

The time interval from admission to delivery was significantly shorter in women with higher dilatation of the cervix (p < 0.02) and in those admitted at a more advanced gestational age (p < 0.05). Forty-eight percent of women with cervical dilatation 0-2 cm delivered in the first 48 h compared to 85% of the women with a dilatation of 3-6 cm. No significant association was found between the length of the cervix and the time interval to delivery.

Conclusion:

Dilatation of the cervix and gestational age at admission are associated with the time interval to delivery in women with preterm labor. The assessment of the length of the cervix is unlikely to add clinical information in women with an already dilated cervix.

Tocolysis for Women With Early Spontaneous Preterm Labor and Advanced Cervical Dilation

OBJECTIVE

To characterize tocolytic use and examine perinatal outcomes among women presenting very preterm with spontaneous labor and cervical dilation 4 cm or greater.

METHODS

This was a retrospective cohort study. Data from January 2000 to June 2011 in a single health care system were reviewed. Women with singleton, nonanomalous fetuses and preterm labor with intact membranes between 23 and 32 weeks of gestation who had cervical dilation 4 cm or greater and less than 8 cm at admission were included. Women receiving one or more tocolytics (magnesium sulfate, indomethacin, or nifedipine) were compared with those who did not receive tocolysis. The primary outcome was composite major neonatal morbidity.

RESULTS

Two hundred ninety-seven women were included; 233 (78.5%) received at least one tocolytic. Women receiving tocolysis were slightly less dilated (median 5 compared with 6 cm, P<.001) at presentation and were more likely to receive at least a partial course of corticosteroids (88.4% compared with 56.3%, P<.001). Initial composite severe neonatal morbidity rates were similar (41.6% compared with 43.8%, P=.761) regardless of tocolytic administration. Those receiving tocolysis were significantly more likely to be pregnant at least 48 hours after admission (23.6% compared with 7.8%, P=.005), but a similar proportion delivered within 7 days of admission (94.8% compared with 95.3%, P>.99), and delivery gestational ages were similar (28.9 compared with 29.2 weeks, P=.408). The incidence of chorioamnionitis and postpartum endometritis was similar between groups.

CONCLUSION

The majority of women presenting very preterm with advanced cervical dilation received tocolysis. Although tocolysis administration increased the likelihood of achieving at least 48 hours of latency, initial neonatal outcomes were similar.

LEVEL OF EVIDENCE

II.

Study protocol: PoPE-Prediction of Preterm delivery by Electrohysterography

Background

Traditional methods used for prediction of preterm delivery are subjective and inaccurate. The Electrohysterogram (EHG) and in particular the estimation of the EHG conduction velocity, is a relatively new promising method for detecting imminent preterm delivery. To date the analysis of the conduction velocity has relied on visual inspection of the signals. As a next step towards the introduction of EHG analysis as a clinical tool, we propose an automated method for EHG conduction velocity estimation for both the speed and direction of single spike propagation.

Methods/Design

The study design will be an observational cohort study. 100 pregnant women, gestational age between 23 + 5 and 34 weeks, admitted for threatening preterm labor or preterm prelabor rupture of membranes, will be included. The length of the cervical canal will be measured by transvaginal ultrasound. The EHG will be recorded using 4 electrodes in a fixed configuration. Contractions will be detected by analysis of the EHG and using an estimation of the intra uterine pressure. In the selected contractions, the delays between channels will be estimated by cross-correlation, and subsequently, the average EHG conduction velocity will be derived. Patients will be classified as labor group and non-labor group based on the time between measurement and delivery. The average conduction velocity and cervical length will be compared between the groups. The main study endpoints will be sensitivity, specificity, and area under the ROC curve for delivery within 1,2,4,7, and 14 days from the measurement.

Discussion

In this study, the diagnostic accuracy of EHG conduction velocity analysis will be evaluated for detecting preterm labor. Visual and automatic detection of contractions will be compared. Planar wave propagation will be assumed for the calculation of the CV vector.

Trial registration

Current Controlled Trials ISRCTN07603227.

Effect of antenatal corticosteroids on respiratory morbidity in singletons after late-preterm birth

OBJECTIVE

To evaluate whether neonates born to women who previously had received antenatal corticosteroids and then delivered a late-preterm-birth neonate had less respiratory morbidity compared with those not exposed to antenatal corticosteroids.

METHODS

This is a secondary analysis from a multicenter observational study regarding mode of delivery after previous cesarean delivery. We compared women who received one course of antenatal corticosteroids with unexposed parturients and evaluated various respiratory outcomes among those having a singleton, late-preterm-birth neonate. We controlled for potential confounders including gestational age at delivery, diabetes, mode of delivery, and maternal race.

RESULTS

Five thousand nine hundred twenty-four patients met the inclusion criteria; 550 received steroids and 5,374 did not. In the univariable model, compared with unexposed women, those who received antenatal corticosteroids appeared more likely to have neonates who required ventilatory support (11.5% compared with 8.6%, P=.022), had respiratory distress syndrome (RDS) (17.1% compared with 12.2%, P=.001), developed transient tachypnea of the newborn (12.9% compared with 9.8%, P=.020), or required resuscitation in the delivery room (55.8% compared with 49.7%, P=.007). After controlling for confounding factors, we found no significant differences among the groups regarding all of the above outcomes with an odds ratio for RDS of 0.78 (95% confidence interval, 0.60-1.02) and ventilator support of 0.75 (95% confidence interval, 0.55-1.03).

CONCLUSION

Exposure to antenatal corticosteroids does not significantly affect respiratory outcomes among those with a subsequent late-preterm birth.

Nifedipine-induced changes in the electrohysterogram of preterm contractions: feasibility in clinical practice

Objective. Evaluating changes in the power spectral density (PSD) peak frequency of the electrohysterogram (EHG) caused by nifedipine in women with preterm contractions. Methods. Calculation of the PSD peak frequency in EHG contraction bursts at different times of nifedipine treatment in women in gestational age 24 to 32 weeks with contractions. Results. A significant (P < .05) decrease of PSD peak frequency between EHG signals measured before and 15 minutes after administration of nifedipine. A significant (P < .05) decrease in PSD peak frequency comparing signals recorded within 24 hours after administration of nifedipine to signals 1 day after tocolytic treatment. A higher average PSD peak frequency for patients delivering within 1 week than that for patients delivering after 1 week from nifedipine treatment (P > .05). Conclusions. EHG signal analysis has great potential for quantitative monitoring of uterine contractions. Treatment with nifedipine leads to a shift to lower PSD peak frequency in the EHG signal.

Efficacy of aggressive tocolysis for preterm labor with advanced cervical dilatation

OBJECTIVE

Study the effectiveness of tocolysis for preterm labor with advanced cervical dilatation ( > or = 3 cm) to achieve sufficient latency for the effect of steroids to occur, and delivery of more mature neonates.

STUDY DESIGN

We studied 249 singleton pregnancies, 23-36 weeks gestation in preterm labor, stratified by weeks of gestation and degree of cervical dilatation (Group A: 117, < 3 cm; Group B: 132, 3 cm) who were given tocolysis and compared for the length of latency and neonatal outcome.

RESULTS

Maternal characteristics were similar between groups except African-American women were admitted with more advanced cervical dilatation. Latency 72 hours was achieved in Group A: > 75% at all gestational ages, and Group B: > 50%. Latency > or = 72 hours, according to the degree of cervical dilatation, was for Group A: 90%, for Group B: 50-75% from > 3-5 cm dilatation, and 40% at 5.1-6 cm dilatation. Neonatal morbidity was mild with a decreased risk of long-term disability.

CONCLUSIONS

Aggressive tocolytic therapy for preterm labor with advanced cervical dilatation is efficacious, allows for steroid therapy, and allows delivery of more mature neonates.

The validity of cervical dilation as an indication of true labor between 32 and 36 weeks 6 days of gestation

OBJECTIVE

Cervical dilation with regular contraction traditionally has been used to differentiate between true and false labor. This diagnostic criterion has not been tested as most patients receive tocolytics. Our objective was to determine the time from admission to delivery in women with preterm contractions and advanced cervical dilation without tocolytics.

STUDY DESIGN

We reviewed the records of patients with preterm labor on the basis of regular contractions and cervical dilation > or = 3 cm between 32 and 36 weeks 6 days of gestation. Chi-square analysis was performed for delivery at > 1 week.

RESULTS

In the records, 68.8% of the patients remained pregnant at > 1 week without tocolysis. Between 32 and 34 weeks of gestation, the use of tocolysis did not help to prolong pregnancy > 1 week (81% vs 88%; alpha = .05; power = 0.65).

CONCLUSION

Cervical dilation with preterm contraction cannot be used as an indication of true labor. More accurate methods to diagnose true preterm labor and direct management decisions are needed.

Uterine Electromyography Characteristics for Early Diagnosis of Mifepristone-Induced Preterm Labor

OBJECTIVE

Differentiating uterine contractions leading to preterm birth from ineffective uterine activity is difficult with current tools. Uterine electromyographic activity is recordable and consists of bursts (group of action potentials) characterized by characteristics that are different during pregnancy and labor. Our aim was to identify the chronology of the changes in uterine pressure and electromyographic characteristics during mifepristone-induced preterm labor in pregnant rats and to determine the earliest characteristic to change.

METHODS

On day 17 of gestation, intrauterine catheter and electromyography electrodes were implanted in the uterus. On day 18, rats were allocated for treatment with mifepristone or placebo. Intrauterine pressure and electromyography integral activities and electromyography mean were calculated before treatment and 6, 12, 18, 20, 22, and 24 hours after treatment. After mathematical transformation, burst analysis was performed by using power density spectrum energy, peak amplitude, and frequency.

RESULTS

As expected, delivery rate within 24 hours was higher in the mifepristone-treated group. Changes in electromyography integral activity and mean, power density spectrum energy, and intrauterine pressure integral activity occurred late during preterm labor, in a range of 2-4 hours before delivery. Electromyography peak frequency of the power density spectrum exhibited early changes, with a shift from low to high frequencies starting at 12 hours before delivery.

CONCLUSION

Electromyography peak frequency of the power density spectrum from individual bursts was the first characteristic to change after antiprogestin treatment, preceding any change in intrauterine pressure, making it a potentially useful marker for the early diagnosis of preterm labor.

Pregnancy prolongation in women with preterm cervical dilatation utilizing out-patient preterm labor services

OBJECTIVE

To identify the impact of cervical dilatation on pregnancy prolongation in women with hospital evaluation of preterm labor (PTL) symptoms.

METHODS

The study population was identified from a database comprising women receiving out-patient perinatal services. Women diagnosed with PTL, having a singleton gestation, with cervical dilatation of > or =2 cm, intact membranes, and at 22.0-34.9 weeks when hospitalized for evaluation of PTL symptoms were included. Data were analyzed by cervical dilatation at hospital evaluation. The primary study outcome was gestational gain from PTL diagnosis.

RESULTS

A total of 1435 patients were analyzed; mean cervical dilatation at hospitalization was 2.6 +/- 0.7 cm at a mean of 32.4 +/- 2.1 weeks' gestation. Following hospitalization, patients gained a mean of 26.0 +/- 17.2 days. Eighty-seven per cent resumed out-patient services. Approximately 15% delivered within 1 week of PTL evaluation.

CONCLUSION

Even women with advanced cervical dilatation can achieve significant gestational gain. The degree of cervical dilatation has significant impact on latency to delivery in women evaluated for PTL.

Maternal admission characteristics as risk factors for preterm birth

OBJECTIVE

The aim of this study is to identify a subset of women presenting with preterm labor not responding upon tocolytic therapy, eventually resulting in preterm birth.

STUDY DESIGN

The maternal admission characteristics of 185 women with preterm labor receiving tocolysis were analysed for risk factors that could predict which women will deliver within 48 h after the start of tocolysis, or before 34 weeks gestation. Univariate analysis and multivariate logistic regression analysis was performed.

RESULTS

Logistic regression analysis identified the following risk factors for delivery within 48 h after the start of tocolysis: cervical dilatation at admission (odds ratio (OR, cm(-1)) 1.47; 95% confidence interval (CI), 1.44-1.49), elevated leukocyte count at admission (per 10(3) leukocytes/mm(3)) (OR 1.27; 95% CI, 1.26-1.28), use of nifedipine (OR 0.49; 95% CI, 0.26-0.49), and developing signs suggestive of chorioamnionitis following admission (OR 2.12; 95% CI, 1.04-4.33). For delivery before 34 weeks of gestation the following risk factors were identified: use of steroids (OR 5.87; 95% CI, 2.34-14.7), use of nifedipine (OR 0.46; 95% CI, 0.27-0.85), developing signs suggestive of chorioamnionitis following admission (OR 10.6; 95% CI, 3.1-35.9), and preterm premature rupture of the membranes (OR 12; 95% CI, 4.1-35.2).

CONCLUSIONS

Risk factors associated for delivery within 48 h after starting tocolysis are: cervical dilatation at admission, elevated leukocyte count at admission, and developing signs suggestive of chorioamnionitis following admission. Use of nifedipine was associated with a delay of delivery >48 h. Risk factors associated for delivery within 34 weeks gestation are: use of steroids, developing signs suggestive of chorioamnionitis following admission, and ruptured membranes. Use of nifedipine was associated with a delay >34 weeks.

Tocolyse dans les situations pathologiques particulières

In twin pregnancies, the use of beta-adrenergics is associated with a significantly higher incidence of cardiovascular complications, and calcium channel blockers as well as oxytocin antagonists currently appear as first line agents. After extreme preterm delivery of the first twin and in selected patients, the birth of second twin may be delayed with a mean gain of 10-50 days. In cases of symptomatic placenta previa with mild-to-moderate bleeding, tocolytic agents may be associated with a prolongation of pregnancy and increased birth weight without significant impact on frequency or severity of bleeding. Calcium channel blockers are the drugs of choice in the event of diabetes. Indomethacin is a potent tocolytic, in particular in patients with polyhydramnios. However, it may cause oligohydramnios, premature closure of the ductus arteriosus and intrauterine fetal death when high doses are administered for a duration exceeding 48 to 72 hours, particularly beyond 32 weeks' gestation. The neonatal complications of indomethacin occur frequently. Tocolysis appears to reduce the failure rate of external cephalic version at term.

Does preterm cervical dilatation imply imminent labor in multifetal pregnancies?

OBJECTIVE

Women with multifetal pregnancies are at increased risk of preterm labor and delivery compared with singleton pregnancies. Presentation with advanced cervical dilatation of 3-4 cm is generally regarded as being in the midst of the first stage of labor. The purpose of this report is to present our experience in cases of advanced cervical dilatation and arrested preterm labor in multifetal pregnancies.

METHODS

This study is a retrospective analysis of threatened preterm deliveries in women with multifetal pregnancies. Fifteen cases with advanced cervical dilatation that remained undelivered for at least 10 days are presented and reviewed.

RESULTS

Out of 1219 women presenting with multifetal pregnancies to the high-risk maternity unit, 15 women who presented with advanced cervical dilatation of 3-5 cm and remained undelivered for at least 10 days were identified. Eight women presented with twins and seven with triplets. The mean latency period to delivery was 21.7 days (range 10-43 days). The mean gestational age at diagnosis was 31.3 weeks (range 26.3-35.3 weeks). The mean gestational age at delivery was 34.5 weeks (range 29.5-38.0 weeks). Twelve women delivered vaginally in this group, giving a cesarean section rate of 20%.

CONCLUSIONS

In the women presented in this series advanced cervical dilatation did not lead directly to preterm labor and delivery, we believe due to their having a multifetal gestation. It is possible that dilatation of the cervix in these cases is not a result of preterm labor but rather a relative cervical incompetence resulting from overdistention of the uterus in twins or higher-order gestations. This phenomenon may be underdiagnosed because of a tendency to forego frequent digital examinations remote from term without a clear indication. More information is therefore needed on the mechanism of cervical change during multifetal pregnancy.

Treatment of preterm labor

The ultimate goal of treating preterm labor is to prolong the pregnancy long enough to decrease the incidence of neonatal mortality and morbidity associated with prematurity, while minimizing maternal and fetal risks. There are many controversies in treating preterm labor. Much of this controversy stems from the difficulty in establishing efficacy and safety of interventions and uncertainty of the diagnosis of preterm labor. This article outlines conventional measures and tocolytic therapy directed at prolonging the pregnancy. A review of the effect of tocolytic agents, administration, side effects, and nursing interventions is included. Key words: preterm labor treatment,