Inhibition and augmentation of progesterone production during pregnancy: effects on parturition in rhesus monkeys

The Efficacy of a 3β-Hydroxysteroid Dehydrogenase Inhibitor for the Termination of Mid-Term Pregnancies in Dogs

Simple Summary

The medical termination of unwanted pregnancies in dogs is practiced throughout the world for many reasons, including at the request of animal owners. For these procedures, it is advised to use rapidly effective drugs with minimal side effects. In this study, we investigated trilostane, which decreases progesterone levels, for its efficacy in terminating mid-term pregnancies in dogs, as well as potential side effects. Although trilostane is not a standalone alternative for the termination of pregnancy in dogs, it has been determined that its combined use with another medical agent of known efficacy reduces both the abortion time and potential side effects. Further studies investigating an increased frequency of administration rather than the administration dose could contribute to determining the efficacy of trilostane in dogs.

Abstract

Progesterone (P4) is the only hormone needed to maintain pregnancy in dogs. Therefore, a competitive inhibitor of 3β-hydroxysteroid dehydrogenase (3β-HSD) could be a safe and effective option to terminate pregnancy by inhibiting P4 synthesis. To address this hypothesis, we investigated the efficacy of trilostane (TRL), a competitive inhibitor of 3β-HSD, in terminating pregnancy in dogs. Twenty-one dogs between days 30 and 38 of pregnancy were randomly assigned to one of two treatment groups (trilostane (TRL) and aglepristone (AGL)) and an untreated control (CON) group (n = 7 dogs each). Fetal heart rates (FHRs) (measured at 12 h intervals) and serum P4 concentrations (measured at 6 h intervals) were evaluated. The pregnancy termination rates were 0% and 100% in the TRL and AGL groups, respectively. The decrease in the FHR in the TRL and AGL groups was significantly lower than that observed in the CON group. There was a marked decrease in P4 concentrations in the TRL group 6, 54, and 102 h after the initiation of treatment. The luteal expression of StAR appeared to be weaker in the AGL group than the CON group. In conclusion, although a treatment-induced decrease was observed in plasma P4 concentrations, a seven-day TRL treatment alone was not effective in terminating pregnancies. Further studies are needed on the effects of the prolonged administration of TRL with varying doses and frequencies for the termination of mid-term pregnancy in dogs.

Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple pregnancy

BACKGROUND

Multiple pregnancy is a strong risk factor for preterm birth, and more than 50% of women with a twin pregnancy will give birth prior to 37 weeks' gestation. Infants born preterm are recognised to be at increased risk of many adverse health outcomes, contributing to more than half of overall perinatal mortality. Progesterone is produced naturally in the body and has a role in maintaining pregnancy, although it is not clear whether administering progestogens to women with multiple pregnancy at high risk of early birth is effective and safe. Since publication of this new review in Issue 10, 2017, we have now moved one study (El-Refaie 2016) from included to studies awaiting classification, pending clarification about the study data.

OBJECTIVES

To assess the benefits and harms of progesterone administration for the prevention of preterm birth in women with a multiple pregnancy.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (1 November 2016) and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials examining the administration of a progestogen by any route for the prevention of preterm birth in women with multiple pregnancy. We did not include quasi-randomised or cross-over studies.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed reports identified by the search for eligibility, extracted data, assessed risk of bias and graded the quality of the evidence.

MAIN RESULTS

We included 16 trials, which all compared either vaginal or intramuscular (IM) progesterone with a placebo or no treatment, and involved a total of 4548 women. The risk of bias for the majority of included studies was low, with the exception of three studies that had inadequate blinding, or significant loss to follow-up or both, or were not reported well enough for us to make a judgement. We graded the evidence low to high quality, with downgrading for statistical heterogeneity, design limitations in some of the studies contributing data, and imprecision of the effect estimate. 1 IM progesterone versus no treatment or placebo More women delivered at less than 34 weeks' gestation in the IM progesterone group compared with placebo (risk ratio (RR) 1.54, 95% confidence interval (CI) 1.06 to 2.26; women = 399; studies = 2; low-quality evidence). Although the incidence of perinatal death in the progesterone group was higher, there was considerable uncertainty around the effect estimate and high heterogeneity between studies (average RR 1.45, 95% CI 0.60 to 3.51; infants = 3089; studies = 6; I² = 71%; low-quality evidence). No studies reported maternal mortality or major neurodevelopmental disability at childhood follow-up. There were no clear group differences found in any of the other maternal or infant outcomes (preterm birth less than 37 weeks (RR 1.05, 95% CI 0.98 to 1.13; women = 2010; studies = 5; high-quality evidence); preterm birth less than 28 weeks (RR 1.08, 95% CI 0.75 to 1.55; women = 1920; studies = 5; moderate-quality evidence); infant birthweight less than 2500 g (RR 0.99, 95% CI 0.90 to 1.08; infants = 4071; studies = 5; I² = 76%, moderate-quality evidence)). No childhood outcomes were reported in the trials. 2 Vaginal progesterone versus no treatment or placebo by dose There were no clear group differences in incidence of preterm birth before 34 weeks (average RR 0.90, 95% CI 0.66 to 1.23; women = 1503; studies = 5; I² = 36%; low-quality evidence). Although fewer births before 34 weeks appeared to occur in the progesterone group, the CIs crossed the line of no effect. Incidence of perinatal death was higher in the progesterone group, although there was considerable uncertainty in the effect estimate and the quality of the evidence was low for this outcome (RR 1.23, 95% CI 0.74 to 2.06; infants = 2287; studies = 3; low-quality evidence). No studies reported maternal mortality or major neurodevelopmental disability at childhood follow-up. There were no clear group differences found in any of the other maternal or infant outcomes (preterm birth less than 37 weeks (average RR 0.97, 95% CI 0.89 to 1.06; women = 1597; studies = 6; moderate-quality evidence); preterm birth less than 28 weeks (RR 1.53, 95% CI 0.79 to 2.97; women = 1345; studies = 3; low-quality evidence); infant birthweight less than 2500 g (average RR 0.95, 95% CI 0.84 to 1.07; infants = 2640; studies = 3; I² = 66%, moderate-quality evidence)). No childhood outcomes were reported in the trials. For secondary outcomes, there were no clear group differences found in any of the other maternal outcomes except for caesarean section, where women who received vaginal progesterone did not have as many caesarean sections as those in the placebo group, although the difference between groups was not large (8%) (RR 0.92, 95% CI 0.86 to 0.98; women = 1919; studies = 5; I² = 0%). There were no clear group differences found in any of the infant outcomes except for mechanical ventilation, which was required by fewer infants whose mothers had received the vaginal progesterone (RR 0.70, 95% CI 0.52 to 0.94; infants = 2695; studies = 4).

AUTHORS' CONCLUSIONS

Overall, for women with a multiple pregnancy, the administration of progesterone (either IM or vaginal) does not appear to be associated with a reduction in risk of preterm birth or improved neonatal outcomes. Future research could focus on a comprehensive individual participant data meta-analysis including all of the available data relating to both IM and vaginal progesterone administration in women with a multiple pregnancy, before considering the need to conduct trials in subgroups of high-risk women (for example, women with a multiple pregnancy and a short cervical length identified on ultrasound).

Birth and Neonatal Transition in the Guinea Pig: Experimental Approaches to Prevent Preterm Birth and Protect the Premature Fetus

The guinea pig (Cavia porcellus) displays many features of gestational physiology that makes it the most translationally relevant rodent species. Progesterone production undergoes a luteal to placental shift as in human pregnancy with levels rising during gestation and with labor and delivery occurring without a precipitous decline in maternal progesterone levels. In contrast to other laboratory rodents, labor in guinea pigs is triggered by a functional progesterone withdrawal, which involves the loss of uterine sensitivity to progesterone like in women. In both species the amnion membrane is a major source of labor-inducing prostaglandins, which promote functional progesterone withdrawal by modifying myometrial progesterone receptor expression. These similar features appear to result from convergent evolution rather than closer evolutionally relationship to primates compared to other rodents. Nevertheless, the similarities in the production, metabolism and actions of progesterone and prostaglandins allow information gained in pregnant guinea pigs to be extended to pregnant women with confidence. This includes exploring the effects of pregnancy complications including growth restriction and the mechanisms by which stressful conditions increase the incidence of preterm labor. The relatively long gestation of the guinea pig and the maturity of the pups at birth particularly in brain development means that a greater proportion of brain development happens in utero. This allows adverse intrauterine conditions to make a sustained impact on the developing brain like in compromised human pregnancies. In addition, the brain is exposed to a protective neurosteroid environment in utero, which has been suggested to promote development in the guinea pig and the human. Moreover, in utero stresses that have been shown to adversely affect long term neurobehavioral outcomes in clinical studies, can be modeled successfully in guinea pigs. Overall, these parallels to the human have led to increasing interest in the guinea pig for translational studies of treatments and therapies that potentially improve outcomes following adverse events in pregnancy and after preterm birth.

Prenatal administration of progestogens for preventing spontaneous preterm birth in women with a multiple pregnancy

BACKGROUND

Multiple pregnancy is a strong risk factor for preterm birth, and more than 50% of women with a twin pregnancy will give birth prior to 37 weeks' gestation. Infants born preterm are recognised to be at increased risk of many adverse health outcomes, contributing to more than half of overall perinatal mortality. Progesterone is produced naturally in the body and has a role in maintaining pregnancy, although it is not clear whether administering progestogens to women with multiple pregnancy at high risk of early birth is effective and safe.

OBJECTIVES

To assess the benefits and harms of progesterone administration for the prevention of preterm birth in women with a multiple pregnancy.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (1 November 2016) and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials examining the administration of a progestogen by any route for the prevention of preterm birth in women with multiple pregnancy. We did not include quasi-randomised or cross-over studies.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed reports identified by the search for eligibility, extracted data, assessed risk of bias and graded the quality of the evidence.

MAIN RESULTS

We included 17 trials, which all compared either vaginal or intramuscular (IM) progesterone with a placebo or no treatment, and involved a total of 4773 women. The risk of bias for the majority of included studies was low, with the exception of four studies that had inadequate blinding, or significant loss to follow-up or both, or were not reported well enough for us to make a judgement. We graded the evidence low to high quality, with downgrading for statistical heterogeneity, design limitations in some of the studies contributing data, and imprecision of the effect estimate. 1 IM progesterone versus no treatment or placeboMore women delivered at less than 34 weeks' gestation in the IM progesterone group compared with placebo (risk ratio (RR) 1.54, 95% confidence interval (CI) 1.06 to 2.26; women = 399; studies = 2; low-quality evidence). Although the incidence of perinatal death in the progesterone group was higher, there was considerable uncertainty around the effect estimate and high heterogeneity between studies (average RR 1.45, 95% CI 0.60 to 3.51; infants = 3089; studies = 6; I2 = 71%; low-quality evidence). No studies reported maternal mortality or major neurodevelopmental disability at childhood follow-up.There were no clear group differences found in any of the other maternal or infant outcomes (preterm birth less than 37 weeks (RR 1.05, 95% CI 0.98 to 1.13; women = 2010; studies = 5; high-quality evidence); preterm birth less than 28 weeks (RR 1.08, 95% CI 0.75 to 1.55; women = 1920; studies = 5; moderate-quality evidence); infant birthweight less than 2500 g (RR 0.99, 95% CI 0.90 to 1.08; infants = 4071; studies = 5; I2 = 76%, moderate-quality evidence)). No childhood outcomes were reported in the trials. 2 Vaginal progesterone versus no treatment or placebo by doseThere were no clear group differences in incidence of preterm birth before 34 weeks (average RR 0.83, 95% CI 0.63 to 1.09; women = 1727; studies = 6; I2 = 46%; low-quality evidence). Although fewer births before 34 weeks appeared to occur in the progesterone group, the CIs crossed the line of no effect. Incidence of perinatal death was higher in the progesterone group, although there was considerable uncertainty in the effect estimate and the quality of the evidence was low for this outcome (RR 1.23, 95% CI 0.74 to 2.06; infants = 2287; studies = 3; low-quality evidence). No studies reported maternal mortality or major neurodevelopmental disability at childhood follow-up.There were no clear group differences found in any of the other maternal or infant outcomes (preterm birth less than 37 weeks (average RR 0.97, 95% CI 0.89 to 1.06; women = 1597; studies = 6; moderate-quality evidence); preterm birth less than 28 weeks (RR 1.22, 95% CI 0.68 to 2.21; women = 1569; studies = 4; low-quality evidence); infant birthweight less than 2500 g (RR 0.95, 95% CI 0.88 to 1.03; infants = 3079; studies = 4; I2 = 49%, moderate-quality evidence)). No childhood outcomes were reported in the trials.For secondary outcomes, there were no clear group differences found in any of the other maternal outcomes except for caesarean section, where women who received vaginal progesterone did not have as many caesarean sections as those in the placebo group, although the difference between groups was not large (7%) (RR 0.93, 95% CI 0.88 to 0.98; women = 2143; studies = 6; I2 = 0%). There were no clear group differences found in any of the infant outcomes except for mechanical ventilation, which was required by fewer infants whose mothers had received the vaginal progesterone (RR 0.61, 95% CI 0.48 to 0.77; infants = 3134; studies = 5).

AUTHORS' CONCLUSIONS

Overall, for women with a multiple pregnancy, the administration of progesterone (either IM or vaginal) does not appear to be associated with a reduction in risk of preterm birth or improved neonatal outcomes.Future research could focus on a comprehensive individual participant data meta-analysis including all of the available data relating to both IM and vaginal progesterone administration in women with a multiple pregnancy, before considering the need to conduct trials in subgroups of high-risk women (for example, women with a multiple pregnancy and a short cervical length identified on ultrasound).

Myometrial Progesterone responsiveness and the Control of Human Parturition

OBJECTIVE

The goal of this review is to assess the body of literature addressing the mechanism of progesterone withdrawal in the control of human parturition and in particular the recent advances in testing the hypothesis that human parturition is initiated by decreased myometrial responsiveness to progesterone, ie, functional progesterone withdrawal.

METHODS

Published studies of progesterone responsiveness of the pregnant human myometrium in the context of parturition control were reviewed.

RESULTS

Advances in understanding the molecular basis for progesterone receptor (PR)-mediated control of progesterone responsiveness has led to the hypothesis that functional progesterone withdrawal in human parturition is mediated by specific changes in myometrial PR expression, function, or both. The human PR exists as two major subtypes, PR-A and PR-B. As PR-A represses progesterone actions mediated by PR-B, the extent of progesterone responsiveness is inversely related to the PR-A/PR-B expression ratio. In women, the onset of term labor is associated with a significant increase in the myometrial PR-A/PR-B expression ratio that may facilitate functional progesterone withdrawal. Interestingly, expression of the estrogen receptor-alpha (ERalpha) increases concordantly with the PR-A/PR-B expression ratio in nonlaboring myometrium. This finding indicates that functional estrogen activation and functional progesterone withdrawal are linked.

CONCLUSION

Functional progesterone withdrawal in human parturition is likely mediated by an increase in the myometrial PR-A/PR-B expression ratio and possibly by modulation of coactivator and corepressor proteins. Functional progesterone withdrawal appears to induce functional estrogen activation. Thus, for most of pregnancy, progesterone may decrease myometrial estrogen responsiveness by inhibiting ERalpha expression. Such an interaction would explain why the human myometrium is refractory to the high levels of circulating estrogens for most of pregnancy. At term, functional progesterone withdrawal removes the suppression of ERalpha expression leading to an increase in ERalpha and a concomitant increase in myometrial estrogen responsiveness. Estrogen can then act to transform the myometrium to a contractile phenotype. This model explains why disruption of progesterone action alone triggers the full parturition cascade. The link between functional progesterone withdrawal and functional estrogen activation may be a critical mechanism for the endocrine control of human parturition.

Animal Models to Study Placental Development and Function throughout Normal and Dysfunctional Human Pregnancy

Abnormalities of placental development and function are known to underlie many pathologies of pregnancy, including spontaneous preterm birth, fetal growth restriction, and preeclampsia. A growing body of evidence also underscores the importance of placental dysfunction in the lifelong health of both mother and offspring. However, our knowledge regarding placental structure and function throughout pregnancy remains limited. Understanding the temporal growth and functionality of the human placenta throughout the entirety of gestation is important if we are to gain a better understanding of placental dysfunction. The utilization of new technologies and imaging techniques that could enable safe monitoring of placental growth and function in vivo has become a major focus area for the National Institutes of Child Health and Human Development, as evident by the establishment of the "Human Placenta Project." Many of the objectives of the Human Placenta Project will necessitate preclinical studies and testing in appropriately designed animal models that can be readily translated to the clinical setting. This review will describe the advantages and limitations of relevant animals such as the guinea pig, sheep, and nonhuman primate models that have been used to study the role of the placenta in fetal growth disorders, preeclampsia, or other maternal diseases during pregnancy.

Integrated analysis of miRNA/mRNA network in placenta identifies key factors associated with labor onset of Large White and Qingping sows

Labour onset is a very complex physiological process, and its mechanism is poorly understood. Here, we obtained the mRNA and miRNA expression profiles from the placentas of four groups of sows: Qingping sows 112 days after insemination with signs of labour onset (QS), Qingping sows 114 days after insemination with signs of labour onset (QL), Large White sows 114 days after insemination with signs of labour onset (LL) and Large White sows 112 days after insemination without signs of labour onset (LN). A set of differentially expressed genes, including 2164 mRNAs and 39 miRNAs, were found. A DAVID analysis of these differentially expressed genes revealed their critical roles in response to hormone stimulus, immune response. Cytoscape Network analysis of the functional genes found node mRNAs and that the regulatory network between the node mRNAs and miRNAs was established. A comparison of the sequencing data from the shorter gestation period (QS) and the normal gestation period (QL) indicated that these genes were responsible for the quicker and more sensitive reaction to the regulation of labour onset. This research not only detected the key factors that were involved in labour onset but also provided useful information for the research of gynaecological diseases.

Agonist-Dependent Downregulation of Progesterone Receptors in Human Cervical Stromal Fibroblasts

Progesterone (P(4)) maintains uterine quiescence during the majority of pregnancy, whereas diminished progesterone receptor (PR) expression and/or activity (ie, functional P(4) withdrawal) promotes parturition. To investigate the regulation of PR expression in cervical stroma, fibroblasts from premenopausal hysterectomy specimens were prepared. Greater than 99% of the cultures were vimentin positive (mesenchymal cell marker) with only occasional cytokeratin-8 positivity (epithelial cell marker) and no evidence of CD31-positive (endothelial cell marker) cells. Cells were immunolabeled with antibodies directed against PRs (PR-A and PR-B), estrogen receptor α (ER-α), and glucocorticoid receptor-α/β (GR-α/β). All cells were uniformly immunopositive for ER-α and GR-α/β but did not express PRs. Incubation of cells with 10(-8) mol/L 17β-estradiol induced a time-dependent increase in PR-A and PR-B messenger RNAs (mRNAs) by quantitative real-time polymerase chain reactions and proteins by immunoblotting and immunofluorescence. Incubation of cervical fibroblasts with PR ligands (medroxyprogesterone acetate or Org-2058) downregulated PR-A and PR-B levels. Coincubation of cells with PR ligands plus RU-486, a PR antagonist, partially abrogated agonist-induced receptor downregulation. Dexamethasone, a pure glucocorticoid, had no inhibitory effect on PR expression. These results indicate that progestins and estrogens regulate PR expression in cervical fibroblasts. We postulate that hormonal regulation of PR expression in the cervical stroma may contribute to functional P(4) withdrawal in preparation for parturition.

Prenatal administration of progesterone for preventing preterm birth in women considered to be at risk of preterm birth

BACKGROUND

Preterm birth is a major complication of pregnancy associated with perinatal mortality and morbidity. Progesterone for the prevention of preterm labour has been advocated.

OBJECTIVES

To assess the benefits and harms of progesterone for the prevention of preterm birth for women considered to be at increased risk of preterm birth and their infants.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (14 January 2013) and reviewed the reference list of all articles.

SELECTION CRITERIA

Randomised controlled trials, in which progesterone was given for preventing preterm birth.

DATA COLLECTION AND ANALYSIS

Two review authors independently evaluated trials for methodological quality and extracted data.

MAIN RESULTS

Thirty-six randomised controlled trials (8523 women and 12,515 infants) were included. Progesterone versus placebo for women with a past history of spontaneous preterm birth Progesterone was associated with a statistically significant reduction in the risk of perinatal mortality (six studies; 1453 women; risk ratio (RR) 0.50, 95% confidence interval (CI) 0.33 to 0.75), preterm birth less than 34 weeks (five studies; 602 women; average RR 0.31, 95% CI 0.14 to 0.69), infant birthweight less than 2500 g (four studies; 692 infants; RR 0.58, 95% CI 0.42 to 0.79), use of assisted ventilation (three studies; 633 women; RR 0.40, 95% CI 0.18 to 0.90), necrotising enterocolitis (three studies; 1170 women; RR 0.30, 95% CI 0.10 to 0.89), neonatal death (six studies; 1453 women; RR 0.45, 95% CI 0.27 to 0.76), admission to neonatal intensive care unit (three studies; 389 women; RR 0.24, 95% CI 0.14 to 0.40), preterm birth less than 37 weeks (10 studies; 1750 women; average RR 0.55, 95% CI 0.42 to 0.74) and a statistically significant increase in pregnancy prolongation in weeks (one study; 148 women; mean difference (MD) 4.47, 95% CI 2.15 to 6.79). No differential effects in terms of route of administration, time of commencing therapy and dose of progesterone were observed for the majority of outcomes examined. Progesterone versus placebo for women with a short cervix identified on ultrasound Progesterone was associated with a statistically significant reduction in the risk of preterm birth less than 34 weeks (two studies; 438 women; RR 0.64, 95% CI 0.45 to 0.90), preterm birth at less than 28 weeks' gestation (two studies; 1115 women; RR 0.59, 95% CI 0.37 to 0.93) and increased risk of urticaria in women when compared with placebo (one study; 654 women; RR 5.03, 95% CI 1.11 to 22.78). It was not possible to assess the effect of route of progesterone administration, gestational age at commencing therapy, or total cumulative dose of medication. Progesterone versus placebo for women with a multiple pregnancy Progesterone was associated with no statistically significant differences for the reported outcomes. Progesterone versus no treatment/placebo for women following presentation with threatened preterm labour Progesterone, was associated with a statistically significant reduction in the risk of infant birthweight less than 2500 g (one study; 70 infants; RR 0.52, 95% CI 0.28 to 0.98). Progesterone versus placebo for women with 'other' risk factors for preterm birth Progesterone, was associated with a statistically significant reduction in the risk of infant birthweight less than 2500 g (three studies; 482 infants; RR 0.48, 95% CI 0.25 to 0.91).

AUTHORS' CONCLUSIONS

The use of progesterone is associated with benefits in infant health following administration in women considered to be at increased risk of preterm birth due either to a prior preterm birth or where a short cervix has been identified on ultrasound examination. However, there is limited information available relating to longer-term infant and childhood outcomes, the assessment of which remains a priority.Further trials are required to assess the optimal timing, mode of administration and dose of administration of progesterone therapy when given to women considered to be at increased risk of early birth.

Prevention of preterm delivery by 17 alpha-hydroxyprogesterone caproate in asymptomatic twin pregnancies with a short cervix: a randomized controlled trial

OBJECTIVE

The objective of the study was to evaluate the use of 17 alpha-hydroxyprogesterone caproate (17P) to reduce preterm delivery in women with a twin pregnancy and short cervix.

STUDY DESIGN

This open-label, multicenter, randomized controlled trial included women with a twin pregnancy between 24(+0) and 31(+6) weeks of gestation who were asymptomatic and had a cervical length of 25 mm or less measured by routine transvaginal ultrasound. Women were randomized to receive (or not) 500 mg of intramuscular 17P, repeated twice weekly until 36 weeks or preterm delivery. The primary outcome was time from randomization to delivery. Analysis was performed according to the intent-to-treat principle.

RESULTS

The 17P and control groups did not differ significantly for median [interquartile range] time to delivery: 45 (26-62) and 51 (36-66) days, respectively. However, treatment with 17P was associated with a significant increase in the rate of preterm delivery before 32 weeks.

CONCLUSION

Twice-weekly injections of 17P did not prolong pregnancy significantly in asymptomatic women with a twin pregnancy and short cervix.

Endocrine-immune interactions in pregnant non-human primates with intrauterine infection

Preterm birth remains the most common cause of perinatal mortality. Although the causes of preterm labor are multifactorial and vary according to gestational age, preterm labor and term labor share common cellular and molecular mechanisms, including stimulation of the fetal hypothalamic-pituitary-adrenal (HPA) axis and endocrine/immune system interactions. We have developed a non-human primate experimental model for intrauterine infection and preterm labor using chronically instrumented rhesus monkeys (Macaca mulatta) with timed gestations. We have documented the temporal and quantitative relationships among intrauterine infection, the synthesis and release of proinflammatory cytokines, prostaglandins, and fetal-placental steroid biosynthesis in this model. Infection-induced preterm parturition is characterized by significant elevations in amniotic fluid proinflammatory cytokines and by increases in fetal adrenal steroid biosynthesis, but not by corresponding increases in placental estrogen biosynthesis characteristic of spontaneous parturition. This suggests that activation of the fetal HPA axis by the stress of infection is accompanied by placental dysfunction and also that infection-induced preterm parturition is not dependent upon the increased estrogen biosynthesis observed in spontaneous parturition. These different endocrine and immune responses have important diagnostic and therapeutic implications in the management of preterm labor.

Transabdominal evaluation of uterine cervical length during pregnancy fails to identify a substantial number of women with a short cervix

OBJECTIVE

To assess the diagnostic performance of transabdominal sonographic measurement of cervical length in identifying patients with a short cervix.

METHODS

Cervical length was measured in 220 pregnant women using transabdominal and transvaginal ultrasound (US). Reproducibility and agreement between and within both methods were assessed. The diagnostic accuracy of transabdominal US for identifying cases with a cervical length <25 mm was evaluated.

RESULTS

Twenty-one out of 220 cases (9.5%) had a cervical length <25 mm by transvaginal US. Only 43% (n = 9) of patients with a short cervix were correctly identified by transabdominal US. In patients with a cervical length of <25 mm by transvaginal US, transabdominal measurement of the cervix overestimated this parameter by an average of 8 mm (95% LOAs, -26.4 to 10.5 mm). Among women without a short cervix, transabdominal US underestimated cervical length on average (LOA) by 1.1 mm (95% LOAs, -11.0 to 13.2 mm). Transvaginal US was also more reproducible (intraclass correlation coefficient: (ICC) (0.96; 95% CI, 0.94 to 0.97) based on comparisons between 2D images and immediately acquired 3D volume datasets relative to transabdominal US (ICC: 0.71; 95% CI, 0.57 to 0.84). Transvaginal US detected 13 cases with funneling and six cases with sludge whereas only three cases of funneling and one of sludge were detected by transabdominal US.

CONCLUSION

Transabdominal measurement overestimated cervical LOA by 8 mm among women with a short cervix and resulted in the underdiagnosis of 57% of cases.

Prevention of preterm delivery after successful tocolysis in preterm labor by 17 alpha-hydroxyprogesterone caproate: a randomized controlled trial

OBJECTIVE

The objective of the study was to evaluate the use of 17 alpha-hydroxyprogesterone caproate (17P) to reduce preterm delivery.

STUDY DESIGN

This open-label, multicenter, randomized controlled trial included women with singleton pregnancies admitted at 24-31 weeks' gestation and cervical length less than 25 mm for preterm labor successfully arrested by tocolytic treatment. Randomization assigned them to receive (or not) 500 mg of intramuscular 17P after tocolysis ended, repeated semiweekly until 36 weeks or preterm delivery. The primary outcome was the time from randomization to delivery.

RESULTS

Outcome data were available for 184 of 188 women randomized. The 17P and control groups (similar for most baseline characteristics) did not differ significantly for median [interquartile range] time to delivery (64 [42-79] and 67 [46-83] days, respectively) or rates of delivery before 37, 34, or 32 weeks of gestation or adverse perinatal outcomes.

CONCLUSION

Semiweekly injections of 17P did not prolong pregnancy significantly in women with tocolysis-arrested preterm labor.

Special populations critical care considerations of the morbidly obese pregnant patient

The critically ill pregnant patient poses a unique challenge to the clinician, requiring a thorough understanding of normal and abnormal maternal and fetal physiology associated with pregnancy. The morbidly obese patient presents even greater challenges to the clinician, and morbidity and mortality are proportionately increased. Because increased numbers of obese pregnant women are now admitted to intensive care units, practitioners must be aware of the physiology associated with both pregnancy and obesity. A multidisciplinary approach is imperative to prevent both maternal and fetal morbidity and mortality for these very complex patients, especially when they are admitted to the ICU with critical illness.

Maternal serum progesterone-induced blocking factor at 11-13 weeks' gestation in spontaneous early preterm delivery

OBJECTIVE

Progesterone-induced blocking factor (PIBF) may be the mediator of the pregnancy maintenance effects of progesterone. The aim of this study is to investigate the potential value of measuring the maternal serum concentration of PIBF at 11-13 weeks' gestation in the prediction of spontaneous early preterm delivery.

METHOD

The maternal serum concentration of PIBF at 11-13 weeks was measured by enzyme-linked immunosorbent assay in 25 singleton pregnancies which subsequently delivered spontaneously before 34 weeks, and 75 controls who delivered at or after 37 weeks. The values in the 2 groups were compared by the Mann-Whitney U test.

RESULTS

The median maternal serum concentration of PIBF in women who subsequently delivered before 34 weeks (157.5, interquartile range 99.5-208.8 ng/ml) was not significantly different from the control group delivering at term (167.5, interquartile range 105.0-212.0 ng/ml; p = 0.519).

CONCLUSIONS

In women who have a spontaneous early preterm delivery, the maternal serum levels of PIBF are not altered at 11-13 weeks of gestation.

Progesterone receptor action in leiomyoma and endometrial cancer

Progesterone is a key hormone in the regulation of uterine function. In the normal physiological context, progesterone is primarily involved in remodeling of the endometrium and maintaining a quiescent myometrium. When pathologies of the uterus develop, specifically, endometrial cancer and uterine leiomyoma, response to progesterone is usually altered. Progesterone acts through mainly two isoforms of the progesterone receptor (PR), PRA and PRB which have been reported to exhibit different transcriptional activities. Studies examining the expression and function of the PRs in the normal endometrium and myometrium as well as in endometrial cancer and uterine leiomyoma are summarized here. The clinical use of progestins and the transcriptional activity of the PR on genes specific to endometrial cancer and leiomyoma are described. An increased understanding of the differential expression of PRs and response to progesterone in these two diseases is critical in order to develop more efficient and targeted therapies.

Prevention of Preterm Birth

The preterm birth rate in the USA is nearing 13%. The recent rise has been attributed to increased indicated preterm births and multiple births following artificial conceptions. There are few obstetrical interventions that successfully delay or prevent spontaneous preterm birth or reduce the risk factors leading to indicated preterm birth. On the other hand, there are many strategies that have improved outcomes for those infants who are born preterm. These include the use of corticosteroids for fetal maturation and regionalization of perinatal care for high-risk mothers and their infants. Several interventions, including progesterone use and cerclage, demonstrate promise in reducing spontaneous preterm births. The most pressing need is to better define the populations of pregnant women for whom these and other interventions will effectively reduce preterm birth.

Progesterone withdrawal: key to parturition

Whereas the essential role of progesterone in the maintenance of pregnancy is accepted generally, the mechanisms that suppress progesterone's function near term to allow labor and delivery of the conceptus are still shrouded in uncertainty. In most subprimate placental mammals, the withdrawal of progesterone before the initiation of labor is manifest by a significant drop in circulating progesterone levels, which is due to either luteolysis or changes in placental steroidogenesis, which shunts precursors towards estrogen production. No such events can be demonstrated in human pregnancy. In this review, we shall present a brief historic background of the research that led to the concepts of "progesterone block" and its withdrawal, based on experiments with rabbits and laboratory rodents, and discuss some of the more recent ideas about "functional progesterone withdrawal," in an attempt to bridge the apparent differences between the regulation of parturition in human and subprimate mammals.

Characterization of progesterone receptor isoform expression in fetal membranes

OBJECTIVE

To quantify expression of progesterone receptor (PR) messenger RNA (mRNA) isoforms in fetal membranes, and to determine whether these levels change in culture.

STUDY DESIGN

Placentas from women undergoing term cesarean delivery before labor were collected. Layers of amnion, chorion, and decidua were separated manually, enzymatically digested, and separated further with the use of a density gradient. RNA was extracted immediately and after culture for 48 hours, then analyzed by quantitative reverse transcription polymerase chain reaction for PR-A, PR-B, and beta-2 microglobulin mRNA expression. Separation of cell types was confirmed by immunohistochemistry.

RESULTS

PR isoform expression was identified in fetal membranes, with levels highest in decidua and below the limits of detection in amnion. The ratio of PR-A/PR-B mRNA was not significantly different between cell layers. PR mRNA isoform levels did not differ significantly in fresh versus cultured cells.

CONCLUSION

Quantitative reverse transcription polymerase chain reaction was used to quantitate expression of PR mRNA isoforms in cells of fetal membranes and to validate systems for further study of PR with respect to inflammation, infection, and preterm delivery.

Prenatal administration of progesterone for preventing preterm birth

BACKGROUND

Preterm birth is the major complication of pregnancy associated with perinatal mortality and morbidity and occurs in up to 6% to 10% of all births. Administration of progesterone for the prevention of preterm labour has been advocated.

OBJECTIVES

To assess the benefits and harms of progesterone administration during pregnancy in the prevention of preterm birth.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Specialised Register of Controlled Trials (March 2005), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 3, 2004), MEDLINE (1965 to January 2005), EMBASE (1988 to August 2004), and Current Contents (1997 to August 2004).

SELECTION CRITERIA

All published and unpublished randomised controlled trials, in which progesterone was given by any route for preventing preterm birth.

DATA COLLECTION AND ANALYSIS

Standard methods of the Cochrane Collaboration and the Cochrane Pregnancy and Childbirth Group were used. Evaluation of methodological quality and trial data extraction were undertaken independently by two authors. Results are presented using relative risk with 95% confidence intervals.

MAIN RESULTS

For all women administered progesterone, there was a reduction in the risk of preterm birth less than 37 weeks (six studies, 988 participants, relative risk (RR) 0.65, 95% confidence interval (CI) 0.54 to 0.79) and preterm birth less than 34 weeks (one study, 142 participants, RR 0.15, 95% CI 0.04 to 0.64). Infants born to mothers administered progesterone were less likely to have birthweight less than 2500 grams (four studies, 763 infants, RR 0.63, 95% CI 0.49 to 0.81) or intraventricular haemorrhage (one study, 458 infants, RR 0.25, 95% CI 0.08 to 0.82). There was no difference in perinatal death between women administered progesterone and those administered placebo (five studies, 921 participants, RR 0.66, 95% CI 0.37 to 1.19). There were no other differences reported for maternal or neonatal outcomes.

AUTHORS' CONCLUSIONS

Intramuscular progesterone is associated with a reduction in the risk of preterm birth less than 37 weeks' gestation, and infant birthweight less than 2500 grams. However, other important maternal and infant outcomes have been poorly reported to date, with most outcomes reported from a single trial only (Meis 2003). It is unclear if the prolongation of gestation translates into improved maternal and longer-term infant health outcomes. Similarly, information regarding the potential harms of progesterone therapy to prevent preterm birth is limited. Further information is required about the use of vaginal progesterone in the prevention of preterm birth.

Role of progestogens for the prevention of premature birth

Premature birth represents a major cause of perinatal morbidity and mortality. The short- and long-term sequelae of prematurity have serious consequences for newborn survival and health in later life. In addition, prematurity is a major problem with regard to health expenditure. Despite major progress in obstetrics, perinatology and neonatology, the percentage of premature birth persists and there is even a tendency towards a slight increase. Therefore, besides screening programmes for the detection of vaginal infections, additional therapeutic opportunities must be sought. According to previously published data, vaginal progesterone and intramuscular 17alpha-hydroxyprogesterone caproate should be considered possible treatment options for the prevention of preterm delivery.

5β-Dihydroprogesterone and steroid 5β–reductase decrease in association with human parturition at term

The role of progesterone withdrawal in human parturition continues to provoke controversy. One possible mechanism by which functional progesterone withdrawal may be achieved is by a decrease in the circulating concentration of its bioactive metabolites. The progesterone metabolite 5beta-dihydroprogesterone (5betaDHP) has been shown to be a potent tocolytic in vitro. We quantified plasma concentrations of 5betaDHP in association with the onset of spontaneous labour in women at term and steroid 5beta-reductase mRNA expression in placenta, myometrium, chorion and amnion in relation to parturition, using real time RT-PCR. Serial blood samples were obtained from patients late in pregnancy, before term labour, during term labour and within the first 24 h postpartum. Following organic solvent extraction, steroids including 5betaDHP were separated by high-performance liquid chromatography (HPLC) and then quantified by radioimmunoassay (RIA). 5betaDHP concentration decreased two-fold (P = 0.00001, n = 25) from 0.317 +/- 0.039 nmol/ml to 0.178 +/- 0.017 nmol/ml in association with active labour. Tissue 5beta-reductase mRNA-relative abundance was determined in placenta, myometrium, chorion and amnion obtained from labouring and non-labouring women. In placenta and myometrium, relative expression decreased significantly in association with labour, by about two-fold and 10-fold, respectively. These data are consistent with a possible role for 5betaDHP in the onset of spontaneous human labour. Further studies exploring this hitherto unrecognized endocrinological pathway are indicated.

Progesterone supplementation for preventing preterm birth: a systematic review and meta-analysis

AIM

The aim of this study is to assess the role of progesterone in preterm birth prevention.

METHODS

A MEDLINE search (from 1966 to the present; date of last search January 2005) was performed - using the key words progesterone, pregnancy, preterm birth, preterm labor, and randomized, controlled trial - in order to identify randomized, controlled trials in which progesterone (either intramuscular or vaginal administration) was compared with placebo or no treatment. Data were extracted and a meta-analysis was performed.

RESULTS

Seven randomized, controlled trials were identified. Women who received progesterone were statistically significantly less likely to give birth before 37 weeks (seven studies, 1020 women, RR = 0.58, 95% CI = 0.48-0.70), to have an infant with birth weight of < or =2.5 kg (six studies, 872 infants, RR = 0.62, 95% CI = 0.49-0.78), or to have an infant diagnosed with intraventricular hemorrhage (one study, 458 infants, RR = 0.25, 95% CI = 0.08-0.82).

CONCLUSIONS

For progesterone supplementation to be advocated for women at the risk of preterm birth, the prolongation of gestation demonstrated in this meta-analysis must translate into improved infant outcomes, including a reduction in mortality. There is currently insufficient information to allow recommendations regarding the optimal dose, route, and timing of administration of progesterone supplementation.

Differences in the endocrine and behavioral profiles during the peripartum period in macaques

The present investigation aims to assess the changes in both social interaction and sex steroids excreted in feces of group-living Japanese macaques and rhesus monkeys. By comparing profiles of estrone conjugates (E1C) and pregnanediol-glucuronide (PdG) with the behavioral propensities of two closely related species living in similar environments, we could test the hypothesis that the social behavior of pregnant females shows significant hormonally mediated changes during the late prepartum and early postpartum period. We found a general tendency to withdraw from social life across pregnancy in both species. These behavioral changes were paralleled by endocrine profiles showing a slight prepartum increase in E1C during the last week in the rhesus group, whereas the increase was more marked and continuous in the Japanese macaque group. PdG increased slightly in rhesus macaques, whereas in Japanese macaques the fluctuations were not significant. Postpartum, both hormones dropped to low levels in both species, with no significant variation therein. Consequent to these changes, the E1C/PdG ratio increased significantly in late pregnancy only in the Japanese macaque group. Overall, these results show significant differences in the social behavior and endocrine profiles of two closely related species, thus complementing previous findings and indicating species-specific characteristics of the association between changes in affiliative behaviors and hormonal fluctuations. In particular, the shift between grooming performed and self-grooming, which showed the closest association with variations in the E1C/PdG ratio, could represent a reliable indicator of the change in the internal status of pregnant females, and is probably functional to infant survival.

The involvement of progesterone in the onset of human labour

Progesterone is essential for the maintenance of pregnancy, and acts to promote uterine quiescence. In many species progesterone levels fall prior to the onset of labour but no fall has been observed in humans. The concept of 'functional' progesterone withdrawal in association with labour has been proposed and a number of mechanisms have been suggested. Recent potential mechanisms of functional withdrawal include changes in progesterone receptor (PR) isoforms, regulation of PR responsive genes through nuclear factor kappaB (NF-kappaB) promoter sites and the non-genomic effects of progesterone or its metabolites.

Reduced binding of progesterone receptor to its nuclear response element after human labor onset

OBJECTIVE

There is indirect evidence of decreased progesterone-activated transcription after human labor onset. Binding of the progesterone receptor to its response element is a prerequisite of progesterone-activated transcription. We established an assay to investigate whether there is reduced binding of progesterone receptor to its nuclear response element after, compared with before, labor onset.

STUDY DESIGN

The binding of progesterone receptor from the decidua to its nuclear response element was measured in gel shift assays. Tissues from 52 patients who were term, preterm, in labor, and not in labor were compared.

RESULTS

A 9-fold decrease in progesterone receptor binding to its response element was observed in tissues obtained after, compared with before, the onset of labor (P = .0008). In both preterm and term not-in-labor tissues, binding was higher than for in-labor tissues (P = .0172 for preterm; P = .0147 for term, Mann-Whitney U test).

CONCLUSION

These findings provide a mechanism for the effective withdrawal of progesterone in human parturition.

Relationship of serum levels of endogenous relaxin to cervical size in the second trimester and to cervical ripening at term

OBJECTIVE

To assess whether cervical size in the early second trimester and cervical ripening at term may be related to serum levels of endogenous relaxin, 17beta-oestradiol or progesterone.

DESIGN

A cross-sectional study investigating the relationship between hormone concentrations and cervical parameters as measured by ultrasound and Bishop score, respectively.

PARTICIPANTS

Uncomplicated human pregnancies with normal fetal outcome, 72 women in the second trimester and 40 women at term.

METHODS

Vaginal ultrasound and palpation were used to estimate cervical parameters. Hormones were analysed either by dissociation-enhanced fluoroimmunoassay (relaxin) or by automated electrochemiluminescent immunoassays.

RESULTS

Cervical length and diameter correlated positively during mid-gestation and negatively at term. During mid-gestation, but not at term, relaxin was significantly associated with cervical length and volume, and with progesterone. Bishop score only correlated inversely with progesterone at term.

CONCLUSION

Corpus luteum function is reflected by progesterone and relaxin in the early second trimester. An impact of relaxin on cervical growth, previously demonstrated by animal models and in vitro experiments, was confirmed during human mid-gestation. In contrast to many other species, human cervical ripening was not associated with endogenous relaxin at term, but with decreased progesterone.

Local paracrine effects of estradiol are central to parturition in the rhesus monkey

The central biochemical mechanisms involved in primate parturition are still unclear. Studies in both humans and nonhuman primates such as the baboon and rhesus monkey indicate that many factors play a part in the cascade of interactive positive feedforward loops that progressively promote parturition: changes in maternal endocrinology, a nocturnal switch in myometrial activity from low amplitude, infrequent contractures to high amplitude, high frequency contractions (see Fig. 1), dilation of the cervix and biochemical changes in the fetal membranes that lead to rupture. Here we demonstrate that infusion of the aromatase inhibitor 4-hydroxyandrostenedione (4OHA) inhibits conversion of androgen to estrogen and prevents premature delivery caused by administration of androgen to pregnant rhesus monkeys at 0.8 of pregnancy term. 4OHA also inhibited the androstenedione induced maternal endocrine and fetal membrane biochemical changes, and alteration of myometrial activity patterns. Secondly, peripheral estrogen infusions increased myometrial activity but did not produce preterm delivery or fetal membrane changes. We conclude that paracrine functions of estrogen at its site of production play critical and central roles in delivery in the non-human primate.