New perspectives for the effective treatment of preterm labor

Hypercholesterolaemia in pregnancy as a predictor of adverse pregnancy outcome

BACKGROUND

Prevention of viable spontaneous preterm birth and low birth weight through screening is one of the key aims of antenatal care as these have implications for the child, mother and society. If women can be identified to be at high risk of these adverse birth outcomes in early pregnancy, they can be targeted for more intensive antenatal surveillance and prophylactic interventions.

OBJECTIVES

This study is therefore aimed to determine the association between elevated maternal serum cholesterol level in pregnancy and adverse pregnancy outcome.

METHODS

It was a prospective observational cohort study in which eligible participants were enrolled at gestational age of 14 to 20 weeks. Blood samples were obtained to measure total serum cholesterol concentrations and the sera were then analyzed enzymatically by the cholesterol oxidase: p-aminophenazone (CHOD PAP) method. Pregnancy outcomes were obtained by extraction from medical records and the labour ward register.

RESULTS

The incidences of the two adverse pregnancy outcomes examined in the study (preterm births and low birth weight (LBW) in term neonates) were 8.0% and 14.4% respectively. Preterm birth was 6.89-times more common in mothers with high cholesterol than in control mothers with normal total cholesterol level (38.5% versus 5.4%, P=0.029) while LBW was 7.99-times more common in mothers with high total maternal cholesterol than in mothers with normal cholesterol (87.5% versus 10.5%, P=0.019).

CONCLUSION

We can infer that the high maternal serum cholesterol (hypercholesterolaemia) is associated with preterm delivery/ low birth weight (LBW) in term infants. However, further validation of these findings with more robust prospective and longitudinal characterization of maternal serum cholesterol profiles is required in subsequent investigations.

Preterm delivery and low maternal serum cholesterol level: Any correlation?

BACKGROUND

The study assessed whether low maternal serum cholesterol during early pregnancy is associated with preterm delivery.

PATIENTS AND METHODS

It was a prospective observational cohort study involving pregnant women at gestational age of 14-20 weeks over a period of 12 months. Blood samples were obtained to measure total serum cholesterol concentrations and the sera were then analysed enzymatically by the cholesterol oxidase: p-aminophenazone (CHOD PAP) method.

RESULTS

The study showed an incidence of 5.0% for preterm delivery in the low risk study patients. Preterm birth was 4.83-times more common with low total maternal cholesterol than with midrange total cholesterol (11.8% versus 2.2%, P = 0.024).

CONCLUSION

Low maternal serum cholesterol (hypocholesterolaemia) is associated with preterm delivery. Optimal maternal serum cholesterol during pregnancy may have merit, therefore pregnant women should be encouraged to follow a healthy, balanced diet.

A Study on the Association between Low Maternal Serum Magnesium Level and Preterm Labour

Objectives. The study was aimed to assess the association between low maternal serum magnesium levels and preterm labour. Methods. It is a cross-sectional case-control study in which eligible participants were pregnant women admitted in labour within the labour ward complex of a Lagos tertiary hospital. Relevant data were extracted from the case records of these women and blood samples were obtained from all participants and serum magnesium levels measured. Results. The study showed that 36% of the study patients had varying degrees of hypomagnesaemia. The relative risk indicates that preterm labour is 1.83 times higher among the patients with low serum magnesium (less than 1.6 mg/dL). The mean difference in serum magnesium levels in both groups was statistically significant (P<0.05). Conclusion. We can infer that low serum magnesium (hypomagnesaemia) is associated with preterm onset of labour. We can, also from this finding, formulate a proposition that would help in preventing preterm labour and birth with the use of prophylactic oral magnesium supplementation among patients with higher risk for development of preterm labour.

Potential influence of the microbiome on infertility and assisted reproductive technology

Although an altered vaginal microbiota has been demonstrated to affect parturition, its role in assisted reproductive technologies is uncertain. Nevertheless, the effect of known pathogens such as Mycoplasma tuberculosis, Chlamydia trachomatis, and Neisseria gonorrhoeae is clear, causing subclinical changes thought to be risk factors in subfertility. The Human Microbiome Project (HMP) has allowed for metagenomic studies to aid in characterizing normal vaginal flora. Recent findings from the HMP demonstrate that many different species of Lactobacillus are present in the vaginal tract, with a few that predominate. Studies that characterize the vaginal microbiome in assisted reproductive technology support the hypothesis that colonizing the transfer-catheter tip with Lactobacillus crispatus at the time of embryo transfer may increase the rates of implantation and live birth rate while decreasing the rate of infection. In addition, there is some evidence that a progesterone-resistant endometrium might increase the risk of an abnormal vaginal microbiome.

Oral betamimetics for maintenance therapy after threatened preterm labour

BACKGROUND

Some women who have threatened to give birth prematurely, subsequently settle. They may then take oral tocolytic maintenance therapy to prevent preterm birth and to prolong gestation.

OBJECTIVES

To assess the effects of oral betamimetic maintenance therapy after threatened preterm labour for preventing preterm birth.

SEARCH METHODS

We updated the search of the Cochrane Pregnancy and Childbirth Group's Trials Register on 9 November 2012.

SELECTION CRITERIA

Randomised controlled trials comparing oral betamimetic with alternative tocolytic therapy, placebo or no therapy, for maintenance following treatment of threatened preterm labour.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the selection criteria and carried out data extraction and quality assessment of studies.

MAIN RESULTS

We did not identify any new trials from the updated search so the results remain unchanged as follows.We included 13 randomised controlled trials (RCTs) with a total of 1551 women. We found no differences for admission to the neonatal intensive care unit when betamimetics were compared with placebo (risk ratio (RR) 1.28, 95% confidence interval (CI) 0.68 to 2.41; two RCTs of terbutaline with 2600 women) or with magnesium (RR 0.80, 95% CI 0.43 to 1.46; one RCT of 137 women). The rate of preterm birth (less than 37 weeks) showed no significant difference in six RCTs, four comparing ritodrine with placebo/no treatment and two comparing terbutaline with placebo/no treatment (RR 1.11, 95% CI 0.91 to 1.35; 644 women). We observed no differences between betamimetics and placebo, no treatment or other tocolytics for perinatal mortality and morbidity outcomes. Some adverse effects such as tachycardia were more frequent in the betamimetics groups than the groups allocated to placebo, no treatment or another type of tocolytic.

AUTHORS' CONCLUSIONS

Available evidence does not support the use of oral betamimetics for maintenance therapy after threatened preterm labour.

Expression of gastrin-releasing peptide is increased by prolonged stretch of human myometrium, and antagonists of its receptor inhibit contractility

Increased uterine stretch appears to increase the risk of preterm labour, but the mechanism is unknown. The aim of this study was to identify factors that mediate the effect of stretch on human myometrium.Myometrial explants, prepared from biopsies obtained at elective caesarean delivery, were either studied acutely, or were maintained in prolonged culture (up to 65 h) under tension with either a 0.6 g or a 2.4 g mass, and compared using in vitro contractility, whole genome array, and qRT-PCR. Tissue held at tonic stretch with the 2.4 g mass for either 24 or 65 h showed increased potassium chloride (KCl)-induced and oxytocin-induced contractility compared with that held with the 0.6 g mass. Gene array identified 62 differentially expressed transcripts after 65 h exposure to increased stretch. Two probes for gastrin-releasing peptide (GRP), a known stimulatory agonist of smooth muscle, were among the top five up-regulated by stretch (3.4-fold and 2.0-fold). Up-regulation of GRP mRNA by stretch was confirmed in a separate series of 10 samples using quantitative RT-PCR (qRT-PCR) (2.8-fold, P =0.01). GRP stimulated contractions acutely when added to freshly obtained myometrial strips in 2 out of 9 cases, but Western blot demonstrated expression of the GRP receptor in 9 out of a further 9 cases. Prolonged incubation of stretched explants in the GRP antagonists PD-176252 or RC-3095 (65 and 24 h, respectively) significantly reduced KCl- and oxytocin-induced contractility.Tonic stretch of human myometrium increases contractility and stimulates the expression of a known smooth muscle stimulatory agonist, GRP. Incubation of myometrium with GRP receptor antagonists attenuates the effect of stretch. GRP may be a target for novel therapies to reduce the risk of preterm birth in multiple pregnancy.

Risk of premature birth in multifetal pregnancy

The risk of preterm delivery ( < 37 weeks of gestation) is approximately nine times higher in women with multifetal pregnancies than in women with singleton pregnancies. However, it is possible that the risk will vary according to gestational week. To assess the risk of premature birth within 1 week by gestational age among multifetal pregnancies and compare the estimated risk with that of singleton pregnancies, we analyzed 6 036 475 infants born in singleton pregnancies and 90 887 infants born in multifetal pregnancies in Japan ( ≥ 22 weeks) over the 5-year period 1989–1993. An estimate of the risk of birth within 1 week at gestational week n was obtained by dividing the number of infants delivered at gestational week n by the number of infants delivered at or beyond gestational week n. The risk at 22 weeks was 0.9 per 1000 fetuses for singleton pregnancies and 5.0 per 1000 for multifetal pregnancies. The risk remained relatively stable until 27 weeks of gestation, then sharply increased toward 36 weeks of gestation in both singleton and multifetal pregnancies. The odds ratio for birth within 1 week for fetuses of multifetal pregnancies compared with fetuses of singleton pregnancies was 5.9 (95% CI, 5.4–6.5) at 22 weeks of gestation, increasing gradually with increasing gestational age until 33 weeks of gestation (13.7; 95% CI, 13.1–14.2) but declining thereafter to 8.8 (95% CI, 8.6–8.9) at 36 weeks of gestation. Results of data analysis for each year of the 5-year period did not differ substantially. Twin Research (2000) 3, 2–6.

The vaginal microbiome: new information about genital tract flora using molecular based techniques

Vaginal microbiome studies provide information that may change the way we define vaginal flora. Normal flora appears dominated by one or two species of Lactobacillus. Significant numbers of healthy women lack appreciable numbers of vaginal lactobacilli. Bacterial vaginosis (BV) is not a single entity, but instead consists of different bacterial communities or profiles of greater microbial diversity than is evident from cultivation-dependent studies. BV should be considered a syndrome of variable composition that results in different symptoms, phenotypical outcomes, and responses to different antibiotic regimens. This information may help to elucidate the link between BV and infection-related adverse outcomes of pregnancy.

Hypotension in normotensive pregnant women treated with nifedipine as a tocolytic drug

OBJECTIVE

To determine hypotensive effect of nifedipine in the treatment of preterm labor.

METHODS

A descriptive analytic study was conducted on pregnant women treated with nifedipine as tocolytic drug for preterm labor. Maternal blood pressure before and at 15, 30, 45 and 60 min after administration of nifedipine was evaluated and analyzed. Hypotension was defined as a decrease in systolic or diastolic blood pressure of 15 mmHg or more.

RESULTS

A total of 157 pregnant women met the inclusion criteria. The mean systolic and diastolic blood pressure before treatment was 109.4 and 72.5 mmHg, respectively. The blood pressure following treatment with nifedipine was significantly decreased both systolic and diastolic blood pressure (p < 0.05) at 30, 45 and 60 min. Of 157 patients, 28 (17.8%) and 27 (17.2%) had systolic and diastolic hypotension, respectively. Of the patients with decreased blood pressure, the mean decrease of systolic and diastolic blood pressure was 16.3 and 14.5 mmHg, respectively.

CONCLUSION

Nifedipine was associated with a minimal but significant decrease in blood pressure. 17% of cases have hypotension. However, hypotension secondary to nifedipine was not associated with significant clinical symptoms, suggesting that nifedipine is relatively safe in terms of hypotensive effect.

Overview. Preterm labour: mechanisms and management

Preterm birth remains a major cause of perinatal mortality and long term handicap in surviving infants. This is one of the most important clinical problems in Europe and across the world. While some preterm births are iatrogenic, associated with severe complications of pregnancy (e.g. hypertensive disorders, antepartum haemorrhage, infection), or the result of multiple pregnancies following assisted reproduction, a high proportion of preterm births occur following spontaneous preterm labour of unknown cause. Early intervention in this group of women would have a significant impact on neonatal mortality and morbidity figures. However, the endocrine changes preceding parturition in women remain elusive and this makes it difficult to predict spontaneous labour at term, let alone preterm labour. Moreover our understanding of myometrial physiology remains rudimentary, limiting our options to devise improved pharmacological strategies to control uterine contractility when this is indicated. There is a need for concerted European and international research efforts to improve our knowledge of the mechanism of labour in women, to identify diagnostic markers to predict preterm labour and to develop uterine selective drugs to inhibit uterine contractions in a safe and efficient manner. This aim will be achieved by multidisciplinary research efforts from academics and industry, using traditional laboratory and clinical research methods, as well as novel technologies.

Cyclic AMP signalling pathways in the regulation of uterine relaxation

Studying the mechanism(s) of uterine relaxation is important and will be helpful in the prevention of obstetric difficulties such as preterm labour, which remains a major cause of perinatal mortality and morbidity. Multiple signalling pathways regulate the balance between maintaining relative uterine quiescence during gestation, and the transition to the contractile state at the onset of parturition. Elevation of intracellular cyclic AMP promotes myometrial relaxation, and thus quiescence, via effects on multiple intracellular targets including calcium channels, potassium channels and myosin light chain kinase. A complete understanding of cAMP regulatory pathways (synthesis and hydrolysis) would assist in the development of better tocolytics to delay or inhibit preterm labour. Here we review the enzymes involved in cAMP homoeostasis (adenylyl cyclases and phosphodiesterases) and possible myometrial substrates for the cAMP dependent protein kinase. We must emphasise the need to identify novel pharmacological targets in human pregnant myometrium to achieve safe and selective uterine relaxation when this is indicated in preterm labour or other obstetric complications.

The regulation of uterine relaxation

The regulation of uterine relaxation is poorly understood but research in myometrial tissue and other types of smooth muscle has defined a number of receptors, ion channels and regulatory proteins that are likely to be involved. Some of these proteins are substrates for protein kinases, especially cyclic nucleotide dependent kinases. More research is necessary to identify the key molecules involved in the maintenance of uterine quiescence in pregnancy. The use of tocolytics in preterm labour remains controversial; there is a need to identify better pharmacological targets to provoke safe and selective uterine relaxation and improve neonatal outcome.

The choice of a tocolytic for the treatment of preterm labor: a critical evaluation of nifedipine versus atosiban

Preterm birth is the major cause of neonatal mortality and morbidity in the developed world. The perfect tocolytic that is uniformly effective with complete fetomaternal safety does not exist. Tocolytic agents differ in cost, utero-specificity, safety, efficacy and whether they are licensed for use. The main three agents that are used worldwide are beta-agonists, Ca(2+) channel blockers and vasopressin/oxytocin receptor antagonists. beta-Agonists are gradually being phased out of use and are being replaced by either nifedipine or atosiban. The evidence base for atosiban is strong but the evidence is of poor quality for nifedipine. The balance of evidence indicates that atosiban is as effective as nifedipine and more effective than beta-agonists and is significantly safer than both. Atosiban was developed specifically to treat preterm labor, so the cost is higher than nifedipine or ritodrine. However, the cost of a course of atosiban (approximately 200 pounds) should not only be considered in comparison with other tocolytic agents but to other medical budgets (e.g., oncology, fertility, cardiology and psychiatry) and to the huge healthcare costs associated with the morbidity and mortality caused by preterm birth. Atosiban is a new advance in the management of spontaneous preterm labor.

Emerging drug therapies for preventing spontaneous preterm labor and preterm birth

Preterm birth (PTB) is the main cause of neonatal mortality and morbidity in the developed world. Historically, the approach for the prevention of PTB has been reactive rather than proactive. With the introduction of new screening tests and a greater emphasis on prevention rather than treatment, a number of new approaches have been introduced that show promise. Progesterone, which is responsible for myometrial quiescence in pregnancy and is used in women with a previous history of PTB, is associated with a significant reduction in the incidence of PTB and low birth weight. Infection is an important cause of PTB in < or = 40% of women. The appropriate antibiotics administered early in pregnancy to women with abnormal genital tract flora have been associated with a 40-60% reduction in the incidence of PTB. Although there has been debate regarding the benefits of nutritional supplementation for the prevention of many complications of pregnancy, recent evidence suggests that fish oil supplementation can be shown to reduce the incidence of PTB in women at risk of PTB. Although these three proactive, preventative approaches show promise, further research is needed to establish the best agent, the optimum gestational age at commencement and cessation, the ideal candidate patient to achieve a response and the long-term feto-maternal benefits and/or side effects.

Use of a novel and highly selective oxytocin receptor antagonist to characterize uterine contractions in the rat

Spontaneous and induced uterine contractions in the rat were found to be inhibited by a novel and selective oxytocin receptor antagonist GSK221149A (3R,6R)-3-Indan-2-yl-1-[(1R)-1-(2-methyl-1,3-oxazol-4-yl)-2-morpholin-4-yl-2-oxoethyl]-6-[(1S)-1-methylpropyl]-2,5-piperazinedione. GSK221149A displayed nanomolar affinity (K(i) = 0.65 nM) for human recombinant oxytocin receptors with >1,400-fold selectivity over human V1a, V1b, and V2 receptors. GSK221149A had similar affinity (K(i) = 4.1 nM) and selectivity for native oxytocin receptors from rat and produced a functional, competitive block of oxytocin-induced contractions in isolated rat myometrial strips with a pA(2) value of 8.18. Intravenous administration of GSK221149A produced a dose-dependent decrease in oxytocin-induced uterine contractions in anesthetized rats with an ID(50) = 0.27 +/- 0.60 mg/kg (corresponding plasma concentrations were 88 ng/ml). Oral administration of GSK221149A (5 mg/kg) was effective in inhibiting oxytocin-induced uterine contractions after single and multiple (4-day) dosing. Spontaneous uterine contractions in late-term pregnant rats (19-21 days gestation) were significantly reduced by intravenous administration of 0.3 mg/kg of GSK221149A. These results provide further evidence that selective oxytocin receptor antagonism may offer an effective treatment for preterm labor.

Care of women at risk of preterm birth: A survey of reported practice in Australia and New Zealand

A mail-out questionnaire on management of women considered at high risk of preterm birth was sent to all members and fellows of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists. While the survey suggested that there is general consensus among practitioners as to what constitutes an increased risk of preterm birth, there is some variation in investigations and treatment currently undertaken.

Incidence of infection for preterm twins cared for in cobedding in the neonatal intensive-care unit

OBJECTIVES

To describe the incidence of infection in a group of cobedded preterm twin infants and compare it to the incidence of infection in a cohort of preterm twin infants cared for in the same institution prior to the onset of cobedding.

DESIGN

Retrospective descriptive design.

SETTING

Tertiary, referral neonatal intensive-care unit in the Midwest.

PARTICIPANTS

Preterm twin infants between 23 and 35 weeks gestational age.

METHODS

Data from 1997 to 2001 (cobedding) compared to data from 1992 to 1996 (no cobedding).

MAIN OUTCOME MEASURE

Infection as evidenced by positive blood, cerebrospinal fluid, or urine culture or radiographic evidence of pneumonia or necrotizing enterocolitis.

RESULTS

Independent samples t test found the cobedded and non-cobedded infants to be homogenous in demographic data. A 2-way analysis of variance demonstrated no significant effects for cobedded infants on number of sepsis evaluations or number of positive blood cultures. There was a statistically significant difference for number of positive blood cultures at discharge reflecting the increased number of positive blood cultures in the non-cobedded infants. Finally, there were no statistically significant differences found between cobedded and non-cobedded for the presence of pneumonia or necrotizing enterocolitis.

CONCLUSIONS

Cobedding of preterm twins cared for in the intensive-care nursery was not associated with an increased incidence of infection. Prospective studies are needed on cobedding before a change in practice is implemented.

Atosiban and nifedipine in acute tocolysis: a comparative study

OBJECTIVE

The objective was to compare the effectiveness, efficacy, and safety of atosiban and nifedipine in preventing or delaying premature labor.

DESIGN

An interventional, randomized, controlled trial of 63 women experiencing preterm labor varying from 24 to 35 completed weeks of gestation. The women were randomized to receive either atosiban intravenously (group I, n=31), or nifedipine orally (group II, n=32).

RESULTS

There were no significant differences in effectiveness and efficacy of tocolysis between the two groups. Women with a history of preterm labor responded significantly better to atosiban than those with no such history. Those at 28 weeks or less responded significantly better to nifedipine, while those at more than 28 weeks' gestation showed an equal response in the two groups. Nifedipine achieved uterine quiescence in a significantly shorter time than atosiban. The maternal side effects were higher with nifedipine. Neonatal complications were comparable in both groups.

CONCLUSIONS

Both drugs are equally effective and efficacious in acute tocolysis. Subgrouping of patients according to gestational age and history of preterm labor may be applied in selecting the line of treatment. The maternal side effects were higher with nifedipine.

Oral betamimetics for maintenance therapy after threatened preterm labour

BACKGROUND

Some women who have threatened to give birth prematurely, subsequently settle. They may then take oral tocolytic maintenance therapy to prevent preterm birth and to prolong gestation.

OBJECTIVES

To assess the effects of oral betamimetic maintenance therapy after threatened preterm labour for preventing preterm birth.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Trials Register (June 2005) and MEDLINE (from 1966 to August 2003).

SELECTION CRITERIA

Randomised controlled trials comparing oral betamimetic with alternative tocolytic therapy, placebo or no therapy, for maintenance following treatment of threatened preterm labour.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the selection criteria and carried out data extraction and quality assessment of studies.

MAIN RESULTS

Eleven randomised controlled trials (RCTs) were included. No differences were seen for admission to the neonatal intensive care unit when betamimetics were compared with placebo (relative risk (RR) 1.29, 95% confidence interval (CI) 0.64 to 2.60; one RCT of terbutaline with 140 women) or with magnesium (RR 0.80, 95% CI 0.43 to 1.46; one RCT of 137 women). The rate of preterm birth (less than 37 weeks) showed no significant difference in four RCTs, two comparing ritodrine with placebo/no treatment and two comparing terbutaline with placebo/no treatment (RR 1.08, 95% CI 0.88 to 1.32, 384 women). No differences between betamimetics and placebo, no treatment or other tocolytics were seen for perinatal mortality and morbidity outcomes. Some adverse effects such as tachycardia were more frequent in the betamimetics groups than the groups allocated to placebo, no treatment or another type of tocolytic.

AUTHORS' CONCLUSIONS

Available evidence does not support the use of oral betamimetics for maintenance therapy after threatened preterm labour.

Comparison of effects of formoterol and BRL 37344 on isolated term-pregnant rat myometrial strips in vitro

This study was designed to compare the effects of beta-adrenoceptor agonists formoterol and BRL 37344 on spontaneous contractions and the levels of cAMP and cGMP of myometrial strips isolated from timed-pregnant rats. Myometrial strips were obtained from term-pregnant Wistar albino rats (n=12), mounted in organ baths and tested for changes in isometric tension in response to formoterol and BRL 37344. We evaluated the effect of increasing concentrations of formoterol and BRL 37344 on oxytocin-induced myometrial contractions and on contractions of myometrial smooth muscle pretreated with metoprolol, ICI 118.551 and SR 59230A (beta1, beta2, beta3-adrenoceptor antagonist, respectively, 10(-6) M). Effects of formoterol and BRL 37344 on cAMP and cGMP levels in isolated myometrial strips (n=6) were evaluated by radioimmunoassay kits. Formoterol (10(-12)-10(-8) M) and BRL 37344 (10(-11)-10(-5) M) concentration-dependently decreased the amplitude of oxytocin-induced contractions. E(max) value (100%) of formoterol was increased significantly more than E(max) value (70.6%) of BRL 37344 (P<0.05), with no change in pD(2) value (9.54+/-0.12 and 9.12+/-0.12, respectively). The inhibition of the amplitude of oxytocin-induced contractions by formoterol was antagonized with ICI 118.551 (10(-6) M), but they were not changed by metoprolol (10(-6) M) or SR 59230A (10(-6) M). The inhibition of the amplitude of oxytocin-induced contractions by BRL 37344 were antagonized with SR 59230A (10(-6) M), but they were not changed by metoprolol (10(-6) M) or ICI 118.551 (10(-6) M). Formoterol and BRL 37344 increased cAMP levels. BRL 37344 increased cGMP levels in BRL 37344 group more than control group, but this increase is less significant than cAMP levels (P>0.05). Formoterol and BRL 37344 decreased amplitude of myometrial contractions with similar potency, but efficacy of formoterol was better than BRL 37344.

The quality of nifedipine studies used to assess tocolytic efficacy: a systematic review

OBJECTIVE

To assess the quality of studies of nifedipine used to treat spontaneous preterm labor.

DESIGN

A systematic review of study quality using a novel validity assessment tool, examining method-specific and topic-specific items in the domains of selection, performance and measurement biases.

DATA SOURCES

Medline (1996-2003), EMBASE (1996-2003), BIOSIS (1993-2003), Current Contents (1995-2003), DERWENT DRUGFILE (1983-2003), Cochrane Database of Systematic Reviews. Bibliographies of existing meta-analyses and systematic reviews of nifedipine as a tocolytic.

METHODS OF STUDY SELECTION

Forty-five studies evaluating the effectiveness of nifedipine were identified.

DATA EXTRACTION

Each study was assessed for 40 method-specific and topic-specific items of quality in duplicate using piloted data extraction forms. Disagreements between assessors were settled by consensus/arbitration.

DATA SYNTHESIS

Very few of the studies complied with adequacy criteria of quality for either method-specific or topic-specific items. There was no improvement in quality over time. The quality of method-specific items was significantly poorer when compared with topic-specific items of quality overall (P<0.0001) and in the domains of selection bias (P<0.0001) and performance bias (P<0.0001).

CONCLUSION

Studies of the effectiveness of nifedipine as a tocolytic are of poorer quality with respect to method-specific items than topic-specific items. These deficiencies should be highlighted in meta-analyses or systematic reviews which measure efficacy and should influence the generation of guideline statements or recommendations for the use of nifedipine as a tocolytic. A large randomized trial fulfilling the quality items is necessary to assess the real efficacy of nifedipine in preterm labor.

Placental lakes on sonographic examination: correlation with obstetric outcome and pathologic findings

PURPOSE

The aim of this study was to compare pregnancy outcome and pathologic findings in cases of placental lake visualized on sonography in pregnancies without concurrent fetal or maternal disease.

METHODS

Placental aspect was evaluated sonographically in 4,106 singleton pregnancies without maternal or fetal disease at between 15 and 34 weeks3 gestation. Fifty-nine cases presenting with placental lakes were followed through the end of pregnancy. Obstetric outcome was compared with that of cases with sonographically normal placental aspects (n=37). Macroscopic and microscopic examinations for pathology were also performed in a few cases in both groups.

RESULTS

Placental lakes were present in 2.2% (92/4,106) of the cases. No statistically significant difference was observed in birth weight, gestational age at delivery, adverse obstetric outcome, and macroscopic or microscopic results between the control and study groups.

CONCLUSION

Our findings do not seem to indicate an increase in the risk for an adverse pregnancy outcome in cases presenting with placental lakes.

Comparison of effects of cyclooxygenase inhibitors on myometrial contraction and constriction of ductus arteriosus in rats

The aim of this study was to compare the tocolytic effect of a selective cyclooxygenase-2 inhibitor, DFU (5,5-dimethyl-3(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2(5H)-furanone), indomethacin and nimesulide on myometrial strips isolated from rats in both lipopolysaccharide-induced preterm labour and term labour. We also compared the constrictor effects of DFU and indomethacin on the fetal ductus arteriosus. Myometrial strips were obtained from preterm and term labour Wistar albino rats and were mounted in organ baths for the recording of isometric tension. DFU, nimesulide and indomethacin significantly inhibited KCl-, oxytocin-, prostaglandin E(2)- and prostaglandin F(2 alpha)-stimulated contractions of myometrial strips isolated from rats in preterm and term labour. The E(max) value of indomethacin was significantly lower than those for DFU and nimesulide (P<0.05), with no change-log (10) EC(50) values. There was no significant difference between in -log (10) EC(50) and E(max) values of DFU and nimesulide for any of the tissues (P>0.05). In addition, there was no significant difference between -log (10) EC(50) and E(max) values for each of these three agents in myometrial tissues isolated from rats in preterm and term labour (P>0.05). Fetal ductus arteriosus was significantly constricted by DFU (10 or 100 mg/kg) in preterm and term rats, although DFU (10 or 100 mg/kg)-induced constriction ratios were significantly lower than those for indomethacin (P<0.05). These data demonstrate that DFU, a specific cyclooxygenase-2 inhibitor, could be considered as a new therapeutic agent for preterm labour. However, careful attention should be given to constriction of the fetal ductus arteriosus.

Lipopolysaccharide induces nitric oxide synthase expression and platelet-activating factor increases nitric oxide production in human fetal membranes in culture

BACKGROUND

Platelet-activating factor and nitric oxide may be involved in the initiation of human labour as inflammatory mediators. The aim of this study was to test whether platelet-activating factor and lipopolysaccharide were able to induce nitric oxide synthase expression and stimulate the production of nitric oxide in human fetal membrane explants in culture.

METHODS

Fetal membranes were collected from Caesarean sections at term. RNA was extracted from membranes and subjected to a qualitative RT-PCR to assess the baseline expression of iNOS. Discs of fetal membranes were cultured for 24 hours in the presence of platelet-activating factor at a dose range of 0.1 nanomolar--1 micomolar or 1 microgram/ml lipopolysaccharide. Nitric oxide production was measured via nitrite ions in the culture medium and mRNA for iNOS was detected by RT-PCR.

RESULTS

Culturing the membrane discs in medium containing serum induced nitric oxide synthase expression and platelet-activating factor significantly stimulated the production of nitric oxide under these conditions. When cultured without serum inducible nitric oxide synthase expression was induced by lipopolysaccharide, but not by platelet-activating factor.

CONCLUSION

Platelet-activating factor may have a role in the initiation of labour, at term or preterm, via the increased local production of nitric oxide as an inflammatory mediator. In this model of intrauterine infection, lipopolysaccharide was found to induce iNOS expression by fetal membranes, and this mechanism could be involved in preterm labour.

Comparison of the effects of nimesulide and 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl) phenyl-2(5H)-furanone (DFU) on contractions of isolated pregnant human myometrium

OBJECTIVE

To compare the effects of 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl) phenyl-2(5H)-furanone (DFU) and nimesulide, selective COX-2 inhibitors, on the amplitude and frequency of KCl-, oxytocin-, and PGF(2alpha)-stimulated contractions of isolated pregnant human myometrial strips.

METHODS

Isolated myometrial strips were obtained from 20 pregnant women undergoing elective cesarean section. These strips were mounted in organ baths for recording of isometric tension. The effects of cumulative concentrations of nimesulide and DFU on KCl-, oxytocin-, and PGF(2alpha)-stimulated myometrial contractions were measured, and values for -log(10)EC(50) and mean maximal inhibition (E(max)) were compared. Nimesulide (10(-8) to 10(-4)M) and DFU (10(-8) to 10(-4)M) inhibited in a concentration-dependent manner the KCl-, oxytocin-, and PGF(2alpha)-stimulated contractions of myometrial strips, with a significant effect on the amplitude (10(-7) to 10(-4)M) and the frequency (10(-6) to 10(-4)M).

RESULTS

The inhibitor effect of DFU was more potent than nimesulide on KCl-, oxytocin-, and PGF(2alpha)-stimulated myometrial contractions, however, the inhibitor effects of nimesulide and DFU was much greater on KCl-stimulated contractions than on oxytocin- and PGF(2alpha)-stimulated myometrial contractions (P < 0.05). There was no significant difference between E(max) values of nimesulide and DFU in all tissues (P > 0.05).

CONCLUSION

DFU is a more potent inhibitor than nimesulide on KCl-, oxytocin-, and PGF(2alpha)-stimulated contractions of pregnant human myometrium. The inhibitor effects of nimesulide and DFU were predominantly on KCl-stimulated contractions.

The role of infection in preterm labour and birth

Preterm birth is the major cause of neonatal mortality and morbidity. Infection is a major cause of preterm labour. Abnormal genital tract flora in early pregnancy is predictive of preterm labour. Antibiotics may be of help in preventing preterm birth.

International Session Award. Non-invasive cutaneous cardiovascular dynamics (CVD) as a predictor of preterm delivery: a pilot study

AIM

To assess the clinical value of cardiovascular dynamics (CVD) pattern of 'positive cycling' in predicting true preterm labor.

METHODS

Patients with a clinical diagnosis of preterm labor had CVD measurement with a non-invasive miniature pressure transducer applied to the fingertip concomitantly with uterine activity monitoring. Based on previous work by our group, the rapid ejection time (RET) reflects arterial compliance; an elevated RET is suggestive of vasoconstriction. Positive cycling is present when the RET shows elevation with uterine contractions and negative cycling is present when there are no changes in the RET with uterine contractions.

RESULTS

Twenty-seven women had negative CVD cycling and nine had positive CVD cycling. There was no difference between the two groups in initial gestational age, cervical effacement or cervical dilation at testing. However, the mean interval from testing to delivery was 1.56 (SEM+/-0.29) days for positive cycling and 39 days (+/-5.25) for negative cycling (P < 0.001).

CONCLUSION

Non-invasive cardiovascular patterns of positive cycling appear predictive of preterm delivery.

An update on the controversies of tocolytic therapy for the prevention of preterm birth

Preterm birth is the major cause of perinatal mortality and morbidity in the developed world. Where there are no contraindications to their use, tocolytics can improve neonatal survival rates by approximately 3% per day between 23 and 27 weeks gestation with a concomitant reduction in morbidity. The ultimate aim of tocolytic therapy is to prolong pregnancy until growth and maturation is complete, but even short-term delay may enable the administration of antepartum glucocorticoids to reduce hyaline membrane disease or to arrange transfer to a center with neonatal intensive care facilities. Both of these have been shown to reduce neonatal mortality and morbidity. Until recently, none of the currently used tocolytics, whether licensed or unlicensed, were developed specifically for the inhibition of preterm labor and consequently, they exhibit various potentially serious side-effects. As a result of the recent licensing of the oxytocin antagonist, atosiban, developed for the treatment of preterm labor and due to its high utero-specificity, obstetricians have experienced an advance in their options for the management of spontaneous preterm labor.

Effect of magnesium sulfate, isradipine, and ritodrine on contractions of myometrium: pregnant human and rat

BACKGROUND

Magnesium sulfate, isradipine, and ritodrine are smooth muscle relaxants used for treating preterm labor. The aim of this study is to investigate the action profile of these drugs on the amplitude and frequency of spontaneous contractions of isolated myometrial strips of pregnant human and rat.

MATERIAL AND METHODS

Isolated myometrial strips were obtained from humans undergoing elective cesarean section at term pregnancy and Wistar albino rats on gestational days 19-21. These strips were mounted in organ baths for recording of isometric tensions. The effect of magnesium sulfate, isradipine, and ritodrine on the amplitude and frequency of spontaneous contractions was compared with the anova test.

RESULTS

Ritodrine (10-8-10-5 M) concentration-dependently inhibited the frequency and amplitude of spontaneous contractions of myometrial strips. At 10-4 M, tachyphylaxis of ritodrine occurred and contractions started again. Magnesium sulfate (10-7-10-4 M) inhibited the frequency but did not change the amplitude of the spontaneous contractions. Isradipine (10-7-10-4 M) had a concentration-related inhibitor effect on both the frequency and amplitude of the spontaneous contractions. The effects of magnesium sulfate, isradipine, and ritodrine were considerably similar in myometrium strips obtained from pregnant rats and humans.

CONCLUSIONS

Because of tachyphylaxis, the effectiveness of ritodrine is limited for inhibition of myometrial contractions. Magnesium sulfate reduced the frequency of spontaneous contractions without affecting the amplitude. Isradipine may be an interesting therapeutic alternative in situations where inhibition of uterine activity is desirable.

Type 2 diabetes management: a comprehensive clinical review of oral medications

Diabetes is a major and growing health problem in the US. An incredible array of different oral medications is now on the market. Clinicians should understand all these new medications and in which clinical picture they will work best.

Calcium channel blockers in the management of preterm labor and hypertension in pregnancy

Calcium channel blockers (CCBs) have the ability to inhibit contractility in smooth muscle cells. CCBs have an already established role in the treatment of non-pregnant hypertension and angina pectoris. Some epidemiological studies found an association between the use of CCBs and an increase in cardiovascular mortality, malignancy, and gastrointestinal bleeding. More recent studies with many more patients and a longer follow-up did not find these associations. In obstetrics CCBs have become increasingly popular for the management of preterm labor and pregnancy-induced hypertensive disorders. Meta-analysis shows that use of nifedipine in comparison with betamimetics is associated with a more frequent successful prolongation of pregnancy in case of preterm labor, resulting in significantly fewer admissions of newborns to the neonatal intensive care unit (NICU), and is associated with a lower incidence of respiratory distress syndrome. No adverse fetal side effects in humans have been reported with the use of nifedipine for obstetric indications. Nifedipine is an effective and safe drug to use when tocolytic therapy is indicated for preterm labor. In preeclampsia nifedipine effectively lowers blood pressure and can be a good alternative for (di) hydralazine.

Effects of erythromycin on stretch-induced contractile activity of isolated myometrium from pregnant women

BACKGROUND

Despite the fact that preterm labor and birth account for the vast majority of neonatal morbidity and mortality the currently available treatment options are still far from satisfactory. The aim of this study was to investigate the effects of erythromycin on stretch-induced contractions of pregnant human myometrial strips, obtained at cesarean section.

METHOD

Myometrial strips were suspended in an organ bath under 3 g tension and the effects of erythromycin (0.1, 0.2, 0.5, 1.0 mM) on stretch-induced isometric contractions were evaluated. Results were statistically analyzed using Kruskal Wallis analysis of variance and Wilcoxon Rank tests where appropriate.

RESULTS

Erythromycin caused a significant decrease in the peak amplitude, while causing an increase in frequency of stretch-induced myometrial contractions in a dose dependent manner in vitro.

CONCLUSIONS

Results from this preliminary study suggest that erythromycin may have additional beneficial effects in infection related preterm labor cases, however, further studies are needed for clarifying the usefulness of erythromycin as a tocolytic agent.

Tocolytic therapy for preterm labour: assessing its potential for reducing preterm delivery

Preterm labour (PTL) is a major contributor to preterm delivery (PTD) but delivery is often not preventable by current therapies. We conducted this study to determine the proportion of women with PTL who were and who were not candidates for tocolytic therapy. The cohort comprised residents of Olmsted County, Minnesota who delivered at >20 weeks' gestation in 1985--94 and who experienced PTL. Medical records were abstracted to identify episodes of PTL, its treatment and outcome. We developed an algorithm that accounted for gestation at delivery and pregnancy complications to determine the proportion of pregnancies complicated by PTL that were candidates for tocolytic therapy. Of 651 pregnancies complicated by PTL, a 50% probability sample, stratified by delivery year, were selected and abstracted. The cumulative incidence of PTL ranged from 3.6 to 6.4 per 100 deliveries of live or stillborn infants. Tocolysis was not contraindicated for 49.4% of all women with PTL and for a third of women with only one PTL episode. Delivery was delayed to >35 weeks in 53.8% of candidates for tocolysis. Only an additional 11.7% of women with one or more PTL episodes could have had their PTD delayed beyond 35 weeks if a perfect tocolytic therapy had been available. Many pregnancies complicated by PTL occurred at > or =35 weeks or involved maternal or obstetric factors that contraindicated tocolytic medications. The maximum incremental benefit that could be expected of a new safe and efficacious tocolytic therapy would be to reduce current PTD rates resulting from PTL by about 12%.

Is there an interaction between cervical length and cervical microbiology in the pathogenesis of preterm labour?

Transvaginal ultrasound of the cervix is increasingly used to estimate cervical length during pregnancy. Initially used to determine a possible need for cervical suture, the technique has been shown to be of value in the prediction of preterm delivery In addition, bacterial vaginosis has been shown to be associated with an increased risk of preterm delivery. We hypothesised that shortening of the cervix and potential cervical pathogens, in particular the presence of bacterial vaginosis, act synergistically in the pathogenesis of premature labour. Three hundred and sixteen women were recruited for prospective longitudinal follow-up, with both transvaginal ultrasound and cervical bacteriology performed at approximately 18 and 28 weeks gestation. A strong correlation was found between a shortened cervix and preterm delivery (p<0.02 at 18 weeks; p<0.001 at 28 weeks). Women with both a short cervix and cervical pathogens had the highest risk of preterm delivery (43%), although not significantly greater than a short cervix with normal cervical flora (31% preterm delivery). In the presence of a normal cervical length, preterm delivery rates in the presence of normal flora and potential cervical pathogens were much lower (9% and 5% respectively).

Prevention of premature birth: do pediatricians have a role?

The rate of prematurity in the United States has increased over the past 15 years despite a reduction in overall infant mortality and birth weight-specific mortality. The major factors contributing to premature birth exist before pregnancy and therefore will require intervention strategies in the pediatric patient. The high-risk factors include young age at conception (16 years), use of illicit drugs and smoking, poor nutritional status, and certain vaginal infections. Pediatric intervention strategies should include sociologic as well as health education stressing heightened self-esteem and communication skills, avoidance of pregnancy and unprotected sexual activity, avoidance of smoking and drug use, and promotion of a good nutritional status.

Double-blind, randomized, controlled trial of atosiban and ritodrine in the treatment of preterm labor: a multicenter effectiveness and safety study

OBJECTIVE

This study was undertaken to compare the efficacy and safety of intravenous administration of atosiban versus ritodrine for the treatment of preterm labor.

STUDY DESIGN

Women with preterm labor and intact membranes diagnosed at 23 to 33 gestational weeks (n = 247) were randomly assigned to treatment arms and received atosiban (6.75 mg intravenous bolus, 300 microg/min for 3 hours, then 100 microg/min intravenously) or ritodrine (0.10-0.35 mg/min intravenously) for as long as 18 hours. Tocolytic effectiveness was assessed in terms of the numbers of women who had not been delivered after 48 hours and after 7 days. Safety was assessed in terms of maternal side effects and neonatal morbidity. Secondary outcomes included mean gestational age at delivery and mean birth weight. An intent-to-treat analysis was performed with the Cochran-Mantel-Haenszel test.

RESULTS

The proportion of women who had not been delivered at 48 hours was 84.9% (n = 107) in the atosiban group and 86.8% (n = 105) in the ritodrine group. At 7 days 92 women had still not been delivered in both the atosiban (73.0%) and ritodrine (76.0%) groups. Neither of these differences was statistically significant. The incidence of maternal cardiovascular side effects was substantially lower in the atosiban group (4.0% vs 84.3%, P <.001). In addition, intravenous therapy was terminated more frequently as a result of maternal adverse events in the ritodrine group (29.8%) than in the atosiban group (0.8%). The overall occurrences of fetal adverse events in the two treatment groups were comparable. Neonatal morbidity was similar between the treatment groups after adjustment for unbalanced enrollment of women with multiple pregnancies and for gestational ages within treatment groups.

CONCLUSION

Atosiban was comparable in clinical effectiveness to conventional ritodrine therapy but was better tolerated than ritodrine, with no evidence of significant maternal or fetal adverse events. Neonatal morbidity, which was similar between the two treatment arms, was apparently related to the gestational age of the infant rather than to the exposure to either tocolytic agent.