Single versus combination tocolytic regimen in the prevention of preterm births in women: a prospective cohort study

OBJECTIVE

Our objective is to compare the efficacy of combination regimen (salbutamol and nifedipine) against single regimen (nifedipine alone) in preventing preterm births among women with preterm labor.

RESULTS

A total of 76 women with gestational age (GA) ranging from 24+0 to 35+6 weeks, who sought treatment for preterm labor with or without cervical dilatation, were recruited for the prospective cohort study. Of these, 38 (50%) had single tocolytic regimen and 38 (50%) had combination tocolytic regimen. The mean GAs at admission were similar for both groups at 31 weeks (±2.93) for Group 1 and 30.9 weeks (±2.88) for Group 2 (P=0.873). The mean GAs at delivery were 37.8 weeks (±1.98) for the single regimen and 36.2 weeks (±3.26) for the combined regimen (P=0.011). The mean tocolytic to delivery interval for the single regimen was longer at 6.74 weeks (±3.13) as compared with 5.21 weeks (±3.61) for the combination regimen (P<0.05). Those on the combination regimen complained of more adverse effects (P<0.001).

CONCLUSION

Our study results suggested that the use of nifedipine as a single tocolytic regimen is as effective as the combination regimen in the delay of preterm births and has much less side effects. Hence, we recommend the sole use of nifedipine for the management of preterm labor.

Medical Transfer of Patients in Preterm Labor: Treatments and Tocolytics

Abstract Objective. To examine the epidemiology, effectiveness, and safety of tocolytics, and the variation in use of standard treatments and predictive testing for women in preterm labor (PTL) transported to tertiary care. Methods. This was a health record review of consecutive PTL patients (<38 weeks gestation) transported to a tertiary care facility by Ontario's air and land critical care transport service between January 1, 2006 and January 1, 2011. The primary outcome was the effectiveness of tocolytics in decreasing the frequency of contractions and incidence of delivery. Secondary outcomes included the type of tocolytics used, adverse events (defined a priori), use of standard treatments (corticosteroid, antibiotic), and use of predictive tests (cervical length measurement, fetal fibronectin). We report descriptive statistics and relative risk of contractions decreasing with tocolytics with 95% confidence intervals. Results. Of the 510 transports reviewed, 488 met all inclusion criteria with the following characteristics: mean age 26.1 years, mean gestational age 31.2 weeks, mean transport time 80 minutes, 61.0% multiparous, 13.3% twins, mean initial dilatation 1.8 cm, contraction <8 min apart 67.7%, and 66.8% from Northern Ontario. Tocolytics were used in 206 (42.2%), with nonsteroidal anti-inflammatory drugs and nitroglycerine being used most frequently. Eleven (2.3%) patients delivered during transport, 4 (36.4%) of which received tocolytics with relative risk (RR) 0.8 (95%CI 0-2.0), and number needed to treat (NNT) 165 (31.5-299.3). Among the 311 (63.7%) patients for which change in contractions was documented, 140 (45%) received tocolytics and of these patients, contractions decreased in 94 (67%), with an RR 0.6 (95%CI 0.3-0.9) and NNT 4.6 (3.1-6.2). Adverse events were documented in 67 (14%) patients (most commonly tachycardia 5.8%). Steroids were appropriately used in 268 (54.9%) patients and antibiotics were appropriately used in 286 (58.6%) patients. Predictive testing was performed in only 19 (3.9%) patients. Conclusions. Tocolytics were associated with decreased contraction frequency in more than two-thirds of those treated. However, nearly half those who did not receive the treatment also had decreased contractions, and the effect did not reach statistical significance. Variation in the type of tocolytic drug used suggests a need for clinical practice guidelines for tocolytic use during transport of PTL patients.

Secondary analysis of the use of transdermal nitroglycerin for preterm labor

OBJECTIVE

This secondary analysis of a randomized placebo-controlled trial was to hypothesize on mechanisms for the improved neonatal outcomes with the use of nitroglycerin (GTN) for preterm labor.

STUDY DESIGN

Women in the original trial who delivered at term were excluded. A composite of severe neonatal outcomes, gestational age at delivery, and corticosteroid use in addition to Kaplan-Meier survival analysis to assess time from randomization to delivery were examined.

RESULTS

A decrease in composite neonatal outcome (relative risk, 0.21; 95% confidence interval, 0.05-0.81; P = .018) with GTN (n = 39) compared with placebo (n = 38) was primarily due to a 23 day prolongation of pregnancy (P = .019) and a trend (P = .04) toward completing a course of corticosteroids in the subgroup randomized prior to 28 weeks' gestation.

CONCLUSION

We hypothesize that GTN has a gestational age-dependent reduction in neonatal outcomes as a result of pregnancy prolongation and corticosteroid administration.

Trends in preterm births in Flanders, Belgium, from 1991 to 2002

Changes in the preterm birth rate have been attributed predominantly to increases in multiple pregnancies, associated with advanced maternal age and assisted reproduction, and to obstetric intervention. We examined their contribution to the frequencies of preterm (<37 weeks), very preterm (<32 weeks) and severely preterm (<28 weeks) birth among 700 383 singleton and twin births in Flanders from 1991 to 2002. We examined changes across four 3-year periods (triennia) with confidence interval [CI] analysis and yearly incremental rates using linear and logistic regression analyses. Over the 12 years, twin pregnancies increased from 1.5% to 2.0%, averaging 1.6% [95% CI 1.54, 1.66] in 1991-93 and 1.9% [95% CI 1.81, 1.94] in 2000-02 (P < 0.001). The proportion of women aged 35 years or more increased from 6.8% [95% CI 6.69, 6.92] in 1991-93 to 11.3% [95% CI 11.2, 11.5] in 2000-02 (P < 0.001) and those aged under 20 from 1.9% [95% CI 1.81, 1.93] to 2.3% [95% CI 2.26, 2.41] (P < 0.001). Assisted reproduction increased from 2.6% [95% CI 2.48, 2.62] to 4.2% [95% CI 4.11, 4.30] (P < 0.001) and obstetric intervention to end pregnancy from 36.2% [95% CI 36.0, 36.4] to 40.3% [95% CI 40.1, 40.6] (P < 0.001). These increases related to an annual increase of 0.23% in the preterm birth rate from 5.5% [95% CI 5.4, 5.6] in 1991-93 to 7.2% [95% CI 7.1, 7.3] in 2000-02 (P < 0.001). The proportions of very and severely preterm births also increased by nearly a third, but their contribution to the total preterm birth rate remained stable at 15% and 5%, respectively. Odds ratios for the increases per year were 1.035 [95% CI 1.032, 1.038] for preterm birth, 1.024 [95% CI 1.018, 1.031] for very preterm and 1.028 [95% CI 1.017, 1.040] for severely preterm births after adjusting for other changes in the population. Overall, the data show, first, marked increases in the frequency of known contributors to the preterm birth rate, including twin pregnancies, advanced maternal age, assisted reproduction and obstetric intervention. Second, the preterm birth rate further increased significantly within subgroups of women with one or more of these characteristics. Third, the preterm birth rate also rose, from 4.4% [95% CI 4.2, 4.5] in 1991-93 to 5.6% [95% CI 5.5, 5.8] in 2000-02 (P < 0.001), in women with none of these contributing factors. This indicates that changes in the frequency of these known predictors are insufficient to explain the steady increase in preterm, very preterm and severely preterm births over more than a decade.

Inflammatory processes enhance cAMP-mediated uterus relaxation in the pregnant rat: the role of TNF-alpha

The objective of this study was to assess the in vitro uterus relaxing potency of beta(2)-adrenergic receptor (beta(2)-AR) agonists in pregnant rats after in utero administration of the bacterial lipopolysaccharide, Escherichia coli endotoxin (LPS). The LPS (100 microg/kg) was injected into the uterine lumen on day 16 of pregnancy. The effects of beta(2)-AR agonist terbutaline was tested in vitro, in isolated uterine rings precontracted by electric field stimulation. Uterine beta(2)-AR densities were detected by radioligand binding assay, the activated G-protein levels were investigated by a radiolabelled GTP binding assay. Uterine cAMP accumulation and the serum tumor necrosis factor-alpha (TNF-alpha) levels were measured by enzyme immunoassay. The endotoxin-evoked preterm delivery occurred on day 21. Higher pD(2) values of terbutaline (p < 0.001) were detected in endotoxin-treated rats: 9.14 +/- 0.36 vs. 7.71 +/- 0.12 compared with sham-operated rats. The densities or the equilibrium dissociation constants of beta(2)-ARs were not different (p > 0.05) in LPS-treated vs. control animals. Serum TNF-alpha level rose threefold after LPS treatment, but this rise was abolished by thalidomide. In LPS + thalidomide-treated rats, the effect of terbutaline became similar to that in sham-operated controls. By the measurement of myometrial cAMP levels, we documented that the concentration-response curve of terbutaline on cAMP accumulation was shifted to the left in the LPS-treated rats, with a significant rise in the pD(2). We concluded that in the case of uterine inflammation, the in vitro uterus-relaxing potency of beta(2)-agonists enhances, which is possibly mediated by TNF-alpha and uterine cAMP levels and that may serve as a rationale for the use of beta(2)-AR agonists in the attenuation of preterm uterine contractions on an inflammatory basis.

Preterm Labour and Birth: A Survey of Clinical Practice Regarding Use of Tocolytics, Antenatal Corticosteroids, and Progesterone

OBJECTIVES

We wished to determine prescribing practices of obstetricians in Canada regarding tocolytics, antenatal corticosteroids, and progesterone for women at increased risk of preterm labour and birth, and to determine whether these practices changed between 1997-98 and 2004.

METHODS

Two cross-sectional surveys of Canadian obstetricians were conducted. The initial survey was in 1997-98 (N = 1313); the follow-up survey was in 2004 (N = 1508).

RESULTS

Response rates were 46.4% in 1997-98 and 43.3% in 2004. Most respondents reported that they prescribed tocolytics to women with signs and symptoms of preterm labour (97.4% in 1997-98; 92.2% in 2004; P < 0.001) but use had decreased. In 1997-98, 20.0% of respondents used tocolytics for > 48 hours during one course of treatment, whereas in 2004, only 9.6% did this (P = 0.06). The tocolytic prescribed most frequently was magnesium sulphate in 1997-98 (40.6% of respondents), whereas in 2004, it was indomethacin (47.5% of respondents). The use of repeat courses of antenatal corticosteroids decreased from 72.9% in 1997-98 to 18.7% in 2004 (P < 0.001). In 2004, only a few respondents (7.0%) prescribed progesterone for women at increased risk of preterm birth.

CONCLUSIONS

Most Canadian obstetricians continue to use tocolytics for women in preterm labour, although use has decreased over time, and the most frequently prescribed tocolytic has changed from magnesium sulphate to indomethacin. The use of repeat courses of antenatal corticosteroids decreased substantially during this time, and in 2004, progesterone was not in frequent use.

The Evaluation of the Fetal Fibronectin Test for Prediction of Preterm Delivery in Symptomatic Patients

OBJECTIVE

This study was conducted to evaluate the usefulness of testing for fetal fibronectin (fFN) to rule out the diagnosis of preterm labour in symptomatic patients in a Canadian setting.

METHODS

This was a prospective, blinded clinical evaluation of fFN testing in women presenting with threatened preterm labour at between 24 and 34 weeks' gestation at two Canadian tertiary care centres.

RESULTS

Of the 149 women tested, 32 had a positive fFN test. In the total patient population, 10.1% delivered within seven days of testing, and 18.2% delivered prior to 34 weeks. A negative fFN result was associated with a 97.4% likelihood of delivering more than seven days after testing and with a 91.4% chance of delivering after 34 weeks.

CONCLUSION

The fFN test appears to provide useful information in the risk assessment of Canadian women presenting with symptoms compatible with preterm labour. A negative test has a high predictive value for delivering more than seven days after presentation.

Racial differences in prenatal care of mothers delivering very low birth weight infants

OBJECTIVES

To determine whether there are any racial differences in the prenatal care of mothers delivering very low birth weight infants (VLBW).

STUDY DESIGN

Retrospective cohort study of infants cared for at a single regional level III neonatal intensive care unit over a 9-year period, July 1993-June 2002, N = 1234. The main outcome variables investigated included antenatal administration of steroids, delivery by cesarean section, and use of tocolytic medications. Both univariate and multivariate analyses were performed.

RESULTS

After controlling for potential confounding variables, white mothers delivering VLBWs had an increased odds of cesarean delivery (odds ratio 1.5, 95% confidence intervals (CI) 1.1-2.0), receiving antenatal steroids (1.3, CI 1.01-1.8), and tocolysis (1.4, CI 1.1-2.0) compared to black mothers. The models controlled for gestational age, multiple gestation, premature labor, clinical chorioamnionitis, maternal age, income, year of birth, and presentation.

CONCLUSIONS

In our population of VLBWs, white mothers are more likely to receive antenatal steroids, tocolytic medications, and deliver by cesarean section when compared to black mothers. From our data we cannot determine the reasons behind these racial differences in care of mothers delivering VLBWs.

Prevalence, Management, and Outcomes of Preterm Prelabour Rupture of the Membranes of Women in Canada

OBJECTIVES

To determine the prevalence of preterm prelabour rupture of the membranes (PPROM) at Canadian university-affiliated perinatal referral centres, to assess the different management strategies, and to review neonatal outcomes.

METHODS

Twelve Canadian university-affiliated perinatal referral centres provided information on their management of PPROM, and 9 participated in data collection to determine prevalence. All women presenting with PPROM during a 2-week period were observed until delivery, and obstetric and neonatal outcome data were subsequently obtained. The total number of deliveries in each centre was recorded for the same time period. We also determined the incidence of PPROM and the neonatal outcome for all women presenting with PPROM at the Kingston General Hospital from January 1999 to December 2001 by retrospective chart review.

RESULTS

In the 9 academic centres, 27 women (1 with a twin pregnancy) presented with PPROM during the 2-week period. There were 1168 deliveries during the same time period, giving a prevalence of PPROM of 2.3%. Overall, 53% of placentas submitted for histopathology after PPROM demonstrated evidence of chorioamnionitis. In the retrospective chart review, we found 153 cases of confirmed PPROM from January 1999 to December 2001,an incidence of 2.8%. Clinical management in all centres was similar for most women who presented with PPROM prior to 34 weeks' gestation. Management after 34 weeks' gestation varied among the 12 centres, ranging from immediate induction of labour to expectant management and induction at a greater gestational age (GA).

CONCLUSIONS

The increased neonatal morbidity associated with PPROM appears to be inversely related to GA. Increased risk of chorioamnionitis is related to increased time from PPROM to delivery.

Epidemiology of preterm birth and neonatal outcome

In industrialized countries, 5-11% of infants are born preterm (<37 weeks' gestation), and the rate has been increasing since the early 1980s. Preterm births account for 70% of neonatal deaths and up to 75% of neonatal morbidity, and contribute to long-term neurocognitive deficits, pulmonary dysfunction and ophthalmologic disorders. In the past several decades, major progress has been made in improving the survival of extremely premature newborns, mostly attributable to timely access to effective interventions that ameliorate prematurity-associated mortality and morbidity such as antenatal administration of corticosteroids and exogenous surfactant therapy, rather than preventing preterm births. However, the societal and healthcare costs to care for survivors with severe morbidity and neurological handicaps remain substantial. Future research should concentrate on the ways to reduce long-term health sequelae and developmental handicaps among survivors of infants born preterm, as well as elucidating the mechanisms and aetiology of preterm births.

What is the future of tocolysis?

Use of the currently available tocolytics is controversial because it has not been associated with improved perinatal outcomes. New markers of preterm labour may come from gene-profiling studies, in as much as they may help in identifying novel genes regulating myometrial quiescence and in expanding our understanding of the pathologic process of uterine dysfunction. Study of certain transcripts in circulating white blood cells by RT-PCR could assist the obstetrician in evaluation of the risks. Uterine electromyography (EMG) also has the potential benefit of monitoring tocolytic treatment, although no standard method of clinical interpretation has yet been devised for the results yielded by this instrumentation. Recent functional genomic studies found that in the uterus at term there is a massive down-regulation of a large panel of developmental cell adhesion molecules and proliferation-related genes. Conversely, maintaining the developmental processes in an active state in patients at risk would help to prevent preterm delivery. It is too early to suggest any therapies with anticytokines in pregnant women. However, exploration of genetic polymorphisms, which may influence the balance of pro- and anti-inflammatory cytokines that are relevant to the course of preterm labour, seems to be a novel avenue that should be explored.