Mechanisms of progesterone action in inhibiting prematurity

Combined vaginal progesterone and cervical cerclage in the prevention of preterm birth: a systematic review and meta-analysis

OBJECTIVE

Vaginal progesterone and cervical cerclage are both effective interventions for reducing preterm birth. It is currently unclear whether combined therapy offers superior effectiveness than single therapy. This study aimed to determine the efficacy of combining cervical cerclage and vaginal progesterone in the prevention of preterm birth.

DATA SOURCES

We searched Medline (Ovid), EMBASE (Ovid), PsycINFO (Ovid), CINAHL (EBSCOhost), Cochrane Library (Wiley), and Scopus (from their inception to 2020).

STUDY ELIGIBILITY CRITERIA

The review accepted randomized and pseudorandomized control trials, nonrandomized experimental control trials, and cohort studies. High risk patients (shortened cervical length <25mm or previous preterm birth) who were assigned cervical cerclage, vaginal progesterone, or both for the prevention of preterm birth were included. Only singleton pregnancies were assessed.

METHODS

The primary outcome was birth <37 weeks. Secondary outcomes included birth <28 weeks, <32 weeks and <34 weeks, gestational age at delivery, days between intervention and delivery, preterm premature rupture of membranes, cesarean delivery, neonatal mortality, neonatal intensive care unit admission, intubation, and birthweight. Following title and full-text screening, 11 studies were included in the final analysis. Risk of bias was assessed using the Cochrane Collaboration tool for assessing the risk of bias (ROBINS-I and RoB-2). Quality of evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) tool.

RESULTS

Combined therapy was associated with lower risk of preterm birth at <37 weeks than cerclage alone (risk ratio, 0.51; 95% confidence interval, 0.37-0.79) or progesterone alone (risk ratio, 0.75; 95% confidence interval, 0.58-0.96). Compared with cerclage only, combined therapy was associated with preterm birth at <34 weeks, <32 weeks, or <28 weeks, decreased neonatal mortality, increased birthweight, increased gestational age, and a longer interval between intervention and delivery. Compared with progesterone alone, combined therapy was associated with preterm birth at <32 weeks, <28 weeks, decreased neonatal mortality, increased birthweight, and increased gestational age. There were no differences in any other secondary outcomes.

CONCLUSION

Combined treatment of cervical cerclage and vaginal progesterone could potentially result in a greater reduction in preterm birth than in single therapy. Further, well-conducted and adequately powered randomized controlled trials are needed to assess these promising findings.

Comparing the efficacy of vaginal micronized progesterone gel and capsule for prevention of preterm birth in singleton pregnancies with short cervical length at midtrimester: an indirect comparison meta-analysis

Objective: To evaluate the effectiveness of vaginal progesterone in preventing preterm birth in women with a singleton gestation and short cervical length and to determine which of the two formulations, micronized progesterone vaginal capsule versus vaginal gel containing micronized progesterone, is more effective for preventing preterm birth. Data sources: A systematic search was performed in the following databases: EMBASE, PubMed (MEDLINE), The Cochrane Library, and the Clinical Trials Registry (clinicaltrials.gov). Study eligibility criteria: Randomized controlled trials (RCTs), prospective and retrospective observational studies were included. We searched for progesterone administration to prevent preterm birth in asymptomatic women with a shortened cervix (<25 mm) measured by ultrasound in the second trimester of singleton pregnancy. Study appraisal and synthesis methods: Assessments of the risk of bias of RCTs were performed by applying the Cochrane Collaboration's Risk of Bias Tool; non-randomized control trials were evaluated with the Newcastle-Ottawa Scale (NOS). The primary outcome was preterm birth ≤33 weeks of gestation. Pooled relative risks (RR) and 95% CI's were calculated for dichotomous outcomes. Heterogeneity of treatment effect was assessed with the I² statistic. We pooled results of the primary outcome for individual studies using a random-effect model. We then performed a network meta-analysis to pool indirect comparisons between the two formulations (gel vs capsule). This analysis was performed using the network meta-analysis package within the R environment. Results: Five studies met the inclusion criteria (4 RCTs, one cohort study) including 1,048 women. The meta-analysis demonstrated that vaginal micronized progesterone significantly reduces preterm birth risk, Risk Ratio = 0.63; 95% CI, 0.48-0.82; p = 0.0006; with no heterogeneity between the studies: I ² = 0%. In the network meta-analysis, no significant difference was demonstrated (OR = 0.85; 95% CI, 0.43-1.69) between the effect of the two formulations of vaginal micronized progesterone (vaginal gel versus vaginal capsules) on the risk of PTB. Conclusion: Vaginal progesterone is associated with a decreased risk of premature birth in women with a shortened cervix in the second trimester of pregnancy. No differences were found between vaginal micronized progesterone in gel or capsule formulations. Systematic Review Registration: PROSPERO, identifier CRD42020165198.

Progesterone, cerclage, pessary, or acetylsalicylic acid for prevention of preterm birth in singleton and multifetal pregnancies - A systematic review and meta-analyses

Background

Preterm birth is the leading cause of childhood mortality and morbidity. We aimed to provide a comprehensive systematic review on randomized controlled trials (RCTs) on progesterone, cerclage, pessary, and acetylsalicylic acid (ASA) to prevent preterm birth in asymptomatic women with singleton pregnancies defined as risk of preterm birth and multifetal pregnancies.

Methods

Six databases (including PubMed, Embase, Medline, the Cochrane Library) were searched up to February 2022. RCTs published in English or Scandinavian languages were included through a consensus process. Abstracts and duplicates were excluded. The trials were critically appraised by pairs of reviewers. The Cochrane risk-of-bias tool was used for risk of bias assessment. Predefined outcomes including preterm birth, perinatal/neonatal/maternal mortality and morbidity, were pooled in meta-analyses using RevMan 5.4, stratified for high and low risk of bias trials. The certainty of evidence was assessed using the GRADE approach. The systematic review followed the PRISMA guideline.

Results

The search identified 2,309 articles, of which 87 were included in the assessment: 71 original RCTs and 16 secondary publications with 23,886 women and 32,893 offspring. Conclusions were based solely on trials with low risk of bias (n = 50).Singleton pregnancies: Progesterone compared with placebo, reduced the risk of preterm birth <37 gestational weeks: 26.8% vs. 30.2% (Risk Ratio [RR] 0.82 [95% Confidence Interval [CI] 0.71 to 0.95]) (high certainty of evidence, 14 trials) thereby reducing neonatal mortality and respiratory distress syndrome. Cerclage probably reduced the risk of preterm birth <37 gestational weeks: 29.0% vs. 37.6% (RR 0.78 [95% CI 0.69 to 0.88]) (moderate certainty of evidence, four open trials). In addition, perinatal mortality may be reduced by cerclage. Pessary did not demonstrate any overall effect. ASA did not affect any outcome, but evidence was based on one underpowered study.Multifetal pregnancies: The effect of progesterone, cerclage, or pessary was minimal, if any. No study supported improved long-term outcome of the children.

Conclusion

Progesterone and probably also cerclage have a protective effect against preterm birth in asymptomatic women with a singleton pregnancy at risk of preterm birth. Further trials of ASA are needed. Prevention of preterm birth requires screening programs to identify women at risk of preterm birth.

Systematic Review Registration

[https://www.crd.york.ac.uk/prospero/], identifier [CRD42021234946].

Progestogens for maintenance tocolysis in symptomatic women. A systematic review and meta-analysis

OBJECTIVE

Prevention of preterm birth (PTB) with progestogens after an episode of threatened preterm labour is still controversial. As different progestogens have distinct molecular structures and biological effects, we conducted a systematic review and pairwise meta-analysis to investigate the individual role played by 17-alpha-hydroxyprogesterone caproate (17-HP), vaginal progesterone (Vaginal P) and oral progesterone (Oral P).

METHODS

The search was performed in MEDLINE, ClinicalTrials.gov and the Cochrane Central Register of Controlled Trials (CENTRAL) up to 31 October 2021. Published RCTs comparing progestogens to placebo or no treatment for maintenance tocolysis were considered. We included women with singleton gestations, excluding quasi-randomized trials, studies on women with preterm premature rupture of membrane, or receiving maintenance tocolysis with other drugs. Primary outcomes were preterm birth (PTB) < 37 weeks' and < 34 weeks'. We assessed risk of bias and evaluated certainty of evidence with the GRADE approach.

RESULTS

Seventeen RCTs including 2152 women with singleton gestations were included. Twelve studies tested vaginal P, five 17-HP, and only 1 oral P. PTB < 34 weeks' did not differ among women receiving vaginal P (RR 1.21, 95%CI 0.91 to 1.61, 1077 participants, moderate certainty of evidence), or oral P (RR 0.89, 95%CI 0.38 to 2.10, 90 participants, low certainty of evidence) as opposed to placebo. Instead, 17-HP significantly reduced the outcome (RR 0.72, 95% CI 0.54 to 0.95, 450 participants, moderate certainty of evidence). PTB < 37 weeks' did not differ among women receiving vaginal P (RR 0.95, 95%CI 0.72 to 1.26, 8 studies, 1231 participants, moderate certainty of evidence) or 17-HP (RR 0.86, 95%CI 0.60 to 1.21, 450 participants, low certainty of evidence) when compared to placebo/no treatment. Instead, oral P significantly reduced the outcome (RR 0.58, 95% CI 0.36 to 0.93, 90 participants, low certainty of evidence).

CONCLUSIONS

With a moderate certainty of evidence, 17-HP prevents PTB < 34 weeks' gestation among women that remained undelivered after an episode of threatened preterm labour. However, data are insufficient to generate recommendations in clinical practice. In the same women, both 17-HP and vaginal P are ineffective in the prevention of PTB < 37 weeks'.

Preterm Birth: An Overview

Birth order has a significant impact on perinatal and long-term outcomes. Preterm birth rates, ranging from 5% to 18%, are regrettably still high in industrialized and developing countries, making them the main contributor to infant mortality and morbidity. Infection, cervical pathology, uterine overdistension, progesterone deficiency, stress on the mother and fetus, allograft reaction, allergic phenomena, and likely more unknown factors are just a few of the causes of preterm birth syndrome. These several causes may improperly stimulate the usual pathway between the decidua and the fetal membranes, resulting in cervical ripening, membrane rupture, and uterine contractility. Some of the mechanisms underpinning these actions include receptors, chemokines, and inflammatory cytokines. For early identification, treatment, and avoidance of negative consequences, it is essential to understand the cellular and metabolic mechanisms that cause preterm labor. Clinicians and researchers are crucial to improving our knowledge of the biochemistry of preterm delivery, identifying risk factors, and creating treatments for this challenging condition. Intrauterine growth restriction and pre-eclampsia or eclampsia are frequent causes of suspected preterm births. "Spontaneous preterm births" occur after preterm labor that develops without warning with an early membrane rupture. It is thought that the condition that may cause these births may have several causes, such as uterine overdistension, vascular disease, infection, or inflammation. Unplanned preterm births have several reasons, including the black race, periodontal disease, low mother body mass index (BMI), and previous preterm births. A short cervical length and a high cervical-vaginal fetal fibronectin concentration are the two best signs of premature birth.

Preserved oxytocin-induced myometrium contraction and sensitivity to progesterone inhibition following rat uterus thermal insult. Impact on fertility

Women seeking improved fertility often undergo diagnostic hysteroscopy that could cause uterine thermal injury with unclear impact on uterine contraction, embryo implantation and fertility. We tested whether uterine thermal insult adversely affects myometrium function and contraction related receptors, channels, junctional proteins and remodeling enzymes. Female Sprague-Dawley rats were anesthetized, the left uterine horn was infused with 85 ℃ hot saline (thermal Insult) and the right horn was infused with 25℃ warm saline (control) for 3 min. After 7-days recovery, uterine strips were prepared for tissue histology and measurement of contraction, and mRNA and protein levels of oxytocin receptor, progesterone (P4) receptor A (PR-A), membrane K⁺ channel TREK-1, junctional protein connexin-43 (CX-43) and matrix metalloproteinases MMP-2 and MMP-9. Uterine tissue histology showed cellular swelling and inflammatory cell infiltration immediately following thermal insult, and recovery with no difference from control 7-days later. KCl (96 mM) and oxytocin (10^-13-10^-7 M) caused significant contraction that was not different in thermal insult vs control uterine strips. Pretreatment with P4 (10^-5 M) for 1 h caused marked inhibition of KCl and oxytocin contraction that was insignificantly greater in thermal vs control uterus. RT-PCR showed decreases in oxytocin receptor, PR-A, TREK-1, CX-43, MMP-2 and MMP-9 mRNA in thermal vs control uterus. Western blots showed decreases in oxytocin receptor, no change in TREK-1 and increased PRA, CX-43, MMP-2, and MMP-9 protein levels in thermal vs control uterus. To assess the impact on fertility, female rats were housed with male rats, and on gestational day 19, the litter size, pup weight and crown-rump length, and placenta weight were not different in thermal vs control uterus. Thus, after thermal insult-induced immediate inflammation and reduced heat-sensitive mRNA expression, the uterus undergoes a recovery and adaptation process involving preserved oxytocin-induced contraction, P4 inhibition and TREK-1 channels. The uterus self-healing process appears to require improved PR-A signaling, intercellular communication via CX-43 and tissue remodeling by MMP-2 and MMP-9. The uterine thermal recovery processes could be essential for maintaining fertility and future pregnancy outcome.

Preventing recurrent preterm birth with 125 mg of 17-alpha-hydroxyprogesterone caproate

AIM

There is strong evidence that weekly intramuscular (IM) injections of 250 mg of 17-alpha-hydroxyprogesterone caproate (17-OHPC) reduce the risk of recurrent preterm birth (PTB); however, whether a lower dose of 17-OHPC could reduce the risk of recurrent PTB remains unclear. This study aimed to assess whether 125 mg of 17-OHPC reduces recurrent PTB among women with a prior singleton spontaneous PTB and cervical length >25 mm.

METHODS

This retrospective cohort study at a tertiary-care medical center in Japan included women with a prior singleton spontaneous PTB between 20 and 36 weeks' gestation and cervical length >25 mm, between 2008 and 2018. Primary outcomes were PTB <37 and <34 weeks' gestation. We calculated the adjusted odds ratio (aOR) and 95% confidence interval (CI) using a multiple logistic regression model. Gestational age at delivery was compared using the Kaplan-Meier survival curve and log-rank test.

RESULTS

Overall, 173 women met the inclusion criteria. Eighty-four women received weekly injections of 125 mg of 17-OHPC, and 89 did not. Treatment with 125 mg of 17-OHPC significantly reduced the risk of recurrent spontaneous PTB <37 (aOR: 0.156 [95% CI: 0.049-0.497]) and <34 weeks' gestation (aOR: 0.156 [95% CI: 0.049-0.497]). The mean delivery gestational age was also significantly longer in the 17-OHPC group (log-rank p = 0.005).

CONCLUSIONS

In this study population, weekly IM injections of 125 mg of 17-OHPC reduced the risk of recurrent PTB <37 and <34 weeks' gestation.

Effectiveness of combined vaginal progesterone and cervical cerclage in preventing preterm birth: a systematic review and meta-analysis protocol

INTRODUCTION

Preterm birth (PTB) is the leading cause of death in children under 5 years. Preventive therapies targeted towards women with risk factors such as a prior PTB or a short cervix reduce the rate of PTB. Cervical cerclage, vaginal progesterone and a combination of the two have been used with no consensus as to whether combined treatment is more effective than any single treatment alone. The objective of this review is to determine the efficacy of combined treatment compared with cerclage alone and combined treatment compared with progesterone alone.

METHODS AND ANALYSIS

Studies will be sourced from the electronic databases Medline (Ovid), EMBASE (Ovid), PsycINFO (Ovid), Scopus, CINAHL (EBSCOhost) and Cochrane Library (Wiley) and reference lists. We will not exclude any papers due to publication date. Randomised control trials (RCTs), non-RCTs and cohort studies assessing single therapy (either progesterone or cerclage) versus combined therapy in women with a singleton pregnancy will be included. Two independent reviewers will conduct study screening (at abstract and full-text level), data extraction and risk of bias assessment with disagreements resolved by an experienced researcher. Random or fixed effects models will be used depending on data heterogeneity and data will be presented as risk ratio for dichotomous data or mean difference for continuous data with a CI of 95% used for all outcomes.

ETHICS AND DISSEMINATION

Not applicable due to nature of the study type.

PROSPERO REGISTRATION NUMBER

CRD42020195975.

Vaginal progesterone for prevention of preterm birth in asymptomatic high-risk women with a normal cervical length: a systematic review and meta-analysis protocol

BACKGROUND

Preterm birth (PTB) is estimated to affect 14.9 million babies globally every year. Global rates of PTB continue to increase from 9.8 to 10.6% over a 15-year period from 2000 to 2014. Vaginal progesterone is commonly used by clinicians as a prevention strategy, with recent evidence affirming the benefit of vaginal (micronised) progesterone to prevent PTB in women with a shortened cervix (< 25 mm). Given the low incidence of a short cervix at mid-gestation in high-risk populations further evidence is required. The objective of this review is to determine if vaginal progesterone reduces spontaneous preterm birth (sPTB) before 37 weeks in asymptomatic high-risk women with a singleton pregnancy with a normal mid-gestation cervical length.

METHODS

Studies will be sourced from MEDLINE, Embase and Cochrane Register of Trials (CENTRAL) from their inception onwards with the search terms 'progesterone' and 'preterm birth'. Studies will be screened and included if they assess vaginal progesterone compared to placebo in women with a normal cervical length. The primary outcome will be sPTB < 37 weeks, with secondary outcomes of sPTB < 34 weeks. Two independent reviewers will conduct study screening at abstract and full text level, data extraction and risk of bias assessment with disagreements resolved by an experienced researcher. The Mantel-Haenszel statistical method and random effects analysis model will be used to produce treatment effect odds ratios and corresponding 95% confidence intervals.

DISCUSSION

This review will assess the current body of evidence and provide clarity regarding the potential benefits and best practice of use of vaginal progesterone in asymptomatic women with high-risk singleton pregnancies and normal cervical length.

TRIAL REGISTRATION

PROSPERO CRD42020152051.

The Feasibility of Cervical Elastography in Predicting Preterm Delivery in Singleton Pregnancy with Short Cervix Following Progesterone Treatment

Previous studies demonstrated an association between cervical strain and risk of spontaneous preterm delivery (sPTD). The present study aimed to assess the efficacy of elastography in predicting sPTD at <32 weeks of gestation in women with singleton pregnancies receiving progesterone for short cervix (≤2.5 cm) diagnosed between 16 and 28 weeks of gestation Among 115 participants eligible for analysis, nine had sPTD at <32 weeks. Preprogesterone (PP0) mean internal os strain (IOS), elasticity contrast index (ECI), hardness ratio (HR), one-week postprogesterone (PP1) IOS, mean external os strain (EOS), ECI, and HR were significantly different between groups. Higher PP0 IOS, PP1 IOS, and PP1 EOS were associated with a 2.92, 4.39 and 3.65-fold increase in the risk of sPTD at <32 weeks, respectively (adjusted for cervical length (CL) at diagnosis; p = 0.04, 0.012 and 0.026, respectively). A combination of CL at diagnosis, PP0 IOS and PP1 EOS showed a significantly higher area under the receiver operating characteristic curve (0.858) than that of CL alone (p = 0.041). In women with singleton pregnancies receiving progesterone for short cervix, cervical elastography performed before and one week after progesterone treatment may be useful in predicting sPTD at <32 weeks of gestation.

Progesterone-induced blocking factor improves blood pressure, inflammation, and pup weight in response to reduced uterine perfusion pressure (RUPP)

Preeclampsia (PE) is characterized by new-onset hypertension in association with elevated natural killer (NK) cells and inflammatory cytokines, which are likely culprits for decreased fetal weight during PE pregnancies. As progesterone increases during normal pregnancy, it stimulates progesterone-induced blocking factor (PIBF). PIBF has been shown to decrease inflammation and cytolytic NK cells, both of which are increased during PE. We hypothesized that PIBF reduces inflammation as a mechanism to improve hypertension in the preclinical reduced uterine perfusion pressure (RUPP) rat model of PE. PIBF (2.0 µg/mL) was administered intraperitoneally on gestational day 15 to either RUPP or normal pregnant (NP) rats. On day 18, carotid catheters were inserted. Mean arterial blood pressure (MAP) and samples were collected on day 19. MAP in NP rats (n = 11) was 100 ± 2 mmHg and 105 ± 3 mmHg in NP + PIBF rats (n = 8) and 122 ± 1 mmHg in RUPP rats (n = 10), which improved to 110 ± 2 mmHg in RUPP + PIBF rats (n = 11), P < 0.05. Pup weight was 2.4 ± 0.1 g in NP, 2.5 ± 0.1 g in NP + PIBF, 1.9 ± 0.1 g in RUPP, and improved to 2.1 ± 0.1 g in RUPP + PIBF rats. Circulating and placental cytolytic NK cells, IL-17, and IL-6 were significantly reduced while IL-4 and T helper (TH) 2 cells were significantly increased in RUPP rats after PIBF administration. Importantly, vasoactive pathways preproendothelin-1, nitric oxide, and soluble fms-Like tyrosine Kinase-1 (sFlt-1) were normalized in RUPP + PIBF rats compared with RUPP rats, P < 0.05. Our findings suggest that PIBF normalized IL-4/TH2 cells, which was associated with improved inflammation, fetal growth restriction, and blood pressure in the RUPP rat model of PE.

Occupational exposure to whole body vibrations and birth outcomes - A nationwide cohort study of Swedish women

BACKGROUND

More women in reproductive ages are entering occupations where exposure to whole body vibrations (WBV) is common (e.g. in transportation and construction). Previous studies based on self-assessed exposure suggest increased risks of adverse birth outcomes, but it is unclear at what exposure levels and if the current exposure guidelines are appropriate during pregnancy.

OBJECTIVES

To investigate whether occupational WBV-exposure increases the risk of preterm birth, low birth weight, and/or small-for-gestational age, in a large, nationwide, prospective, cohort study.

DESIGN

The Fetal Air Pollution Exposure cohort (FAIR) was formed by merging data from multiple, national registers, and the present study includes singletons born 1994-2014 to working women in Sweden (n = 1,091,080 births). WBV-exposure was assessed quantitatively using a job-exposure matrix based on measurements, and calculated odds ratios were adjusted for potential confounders such as smoking and BMI, and other occupational exposures like noise, combustion particles, and physically and psychologically strenuous work. Data on absence from work (full-/part time, sick leave, parental leave, etc.) was also used.

RESULTS

Exposure to WBV during pregnancy, among women with low absence from work (n = 476,419), was associated with an increased risk of preterm birth, below the occupational exposure limit (1.15 m/s²). Compared to unexposed mothers, the OR was 1.38 (95% CI: 1.05, 1.83) for exposure ≥0.5 m/s², corresponding to an increase from 47/1000 cases to 65/1000 cases. No increased risk was found for small-for-gestational age.

CONCLUSIONS

Exposure to WBV was associated with an increased risk of preterm birth. The results suggest that the current permissible exposure and action levels for WBV-exposure do not adequately protect pregnant women with continuous exposure.

17-Hydroxyprogesterone caproate improves hypertension and renal endothelin-1 in response to sFlt-1 induced hypertension in pregnant rats

Preeclampsia (PE) is characterized by new onset hypertension in association with elevated soluble fms-like tyrosine kinase-1 (sFlt-1) and preproendothelin-1 (PPET-1) levels. Currently there is no effective treatment for PE except for early delivery of the fetal placental unit, making PE a leading cause for premature births worldwide. Administration of 17-hydroxyprogesterone caproate (17-OHPC) is used for prevention of recurrent preterm birth. This study was designed to test the hypothesis that 17-OHPC improves hypertension and ET-1 in response to elevated sFlt-1 in pregnant rats. sFlt-1 was infused into normal pregnant (NP) Sprague-Dawley rats (3.7 μg·kg^-1·day^-1 for 6 days, gestation days 13-19) in the presence or absence of 17-OHPC (3.32 mg/kg) administered via intraperitoneal injection on gestational days 15 and 18. Mean arterial blood pressure (MAP), pup and placenta weights, renal cortex PPET-1 mRNA levels and nitrate-nitrite levels were measured on GD 19. Infusion of sFlt-1 into NP rats elevated mean arterial pressure (MAP) compared with control NP rats: 115 ± 1 (n = 13) vs. 99 ± 2 mmHg (n = 12, p < 0.05). 17-OHPC attenuated this hypertension reducing MAP to 102 ± 3 mmHg in sFlt-1 treated pregnant rats (n = 8). Neither pup nor placental weight was affected by sFlt-1 or 17-OHPC. Importantly, renal cortex PPET-1 mRNA levels were elevated 3 fold in NP + sFlt-1 rats compare to NP rats, which decreased with 17-OHPC administration. Plasma nitrate-nitrite levels were 44 ± 9 µM in NP rats (n = 9), 20 ± 3 µM in NP + sFlt-1 (n = 7), which increased to 42 ± 11 µM NP + sFlt-1 + 17OHPC (n = 6). Administration of 17-OHPC improves clinical characteristics of preeclampsia in response to elevated sFlt-1 during pregnancy.

Prenatal Maternal Stress Causes Preterm Birth and Affects Neonatal Adaptive Immunity in Mice

Maternal stress is a well-established risk factor for preterm birth and has been associated with adverse neonatal outcomes in the first and subsequent generations, including increased susceptibility to disease and lasting immunological changes. However, a causal link between prenatal maternal stress and preterm birth, as well as compromised neonatal immunity, has yet to be established. To fill this gap in knowledge, we used a murine model of prenatal maternal stress across three generations and high-dimensional flow cytometry to evaluate neonatal adaptive immunity. We report that recurrent prenatal maternal stress induced preterm birth in the first and second filial generations and negatively impacted early neonatal growth. Strikingly, prenatal maternal stress induced a systematic reduction in T cells and B cells, the former including regulatory CD4+ T cells as well as IL-4- and IL-17A-producing T cells, in the second generation. Yet, neonatal adaptive immunity gained resilience against prenatal maternal stress by the third generation. We also show that the rate of prenatal maternal stress-induced preterm birth can be reduced upon cessation of stress, though neonatal growth impairments persisted. These findings provide evidence that prenatal maternal stress causes preterm birth and affects neonatal immunity across generations, adverse effects that can be ameliorated upon cessation.

Retrospective study of the recurrence risk of preterm birth in Japan

Background: A history of preterm birth is a risk factor for preterm birth in a future pregnancy, and there are some reports of prevention methods, such as the administration of progesterone. However, the rate of recurrence of preterm birth in Japan has not been clarified, and there is no data for judging whether these preventive methods are effective.Objective: To clarify the risk of recurrence of preterm birth and preterm prelabor rupture of membranes (pPROM) in Japan.Materials and methods: A retrospective study was conducted using the perinatal registration database of the Japan Obstetrics and Gynecology Society for the Perinatal Center from 2014 to 2016. There were 704,418 subjects, of which 190,990 were excluded those with unknown maternal information, those under the age of 20 years, those with perinatal disease related to preterm birth, and first-time mothers.Results: Logistic model unavailable and multivariate analysis were performed. An analysis of the preterm birth history indicated the risk of preterm birth in the current pregnancy, and the odds ratio for preterm birth recurrence once, twice, and three times or more was 3.3, 6.6, and 7.8, respectively. As a secondary analysis, we analyzed whether the history of pPROM is a risk factor of recurrence of pPROM and found a significant association with an odds ratio of 3.4.Conclusion: Having a preterm birth history increases the risk of recurrence of preterm birth, and the risk of recurrent preterm birth increases as the number of preterm births increases. Although this report is intended for high-risk pregnancies wherein the rate of preterm birth is high, as previously reported, our data indicate that in Japan, preterm birth is a risk factor of recurrent preterm birth.

17-Hydroxyprogesterone caproate improves T cells and NK cells in response to placental ischemia; new mechanisms of action for an old drug

Preeclampsia (PE) is new onset hypertension during pregnancy associated with increased uterine artery resistance (UARI) and an imbalance among CD4 + T lymphocytes and natural killer (NK) cells. We have shown an important role for 17-hydroxyprogesterone caproate (17-OHPC) to improve hypertension and fetal demise in the RUPP rat model of PE. However we have not examined a role for 17-OHPC to improve NK cells and CD4⁺TH2 cells as possible mechanisms for improved fetal weight and hypertension. Therefore, we hypothesized that 17-OHPC lowers NK cells while improving the T cell ratio in the RUPP rat. RUPP was surgically induced on gestational day 14 in pregnant rats. 17-OHPC (3.32 mg/kg) was administered intraperitoneal on day 15, UARI was measured on day 18. Blood pressure (MAP), blood and tissues were collected on GD 19. MAP in NP rats (n = 9) was 100 ± 2, 104 ± 6 in Sham rats (n = 8), 128 ± 2 in RUPP (n = 11) and 115 ± 3 mmHg in RUPP + 17-OHPC (n = 10), p < 0.05. Pup weight and UARI were improved after 17-OHPC. Total and cytolytic placental NK cells were 38 ± 5, and 12 ± 2% gate in RUPP rats which decreased to 1.6 ± 0.5 and 0.4 ± 0.2% gate in RUPP + 17OHPC rats. CD4⁺ T cells were 40 ± 3 in RUPP rats, which significantly decreased to 7 ± 1 RUPP + 17-OHPC rats. Circulating and placental TH2 cells were 6.0 ± 1, 0.3 ± 0.1% gate in RUPP rats and 12 ± 1%, 2 ± 0.5% gate in RUPP + 17-OHPC rats, p < 0.05 This study identifies new mechanisms whereby 17-OHPC improves outcomes in response to placental ischemia.

Should phenotype of previous preterm birth influence management of women with short cervix in subsequent pregnancy? Comparison of vaginal progesterone and Arabin pessary

OBJECTIVE

To investigate whether the classification of a previous spontaneous preterm birth (sPTB) as preterm labor (PTL) with intact membranes (IM) or as preterm prelabor rupture of membranes (PPROM) impacts the efficacy of cervical pessary or vaginal progesterone for prevention of sPTB in pregnant women with short cervix on transvaginal ultrasound.

METHODS

This was a retrospective cohort study of asymptomatic high-risk singleton pregnancies with a short cervix and history of sPTB, treated using Arabin pessary or vaginal progesterone for primary PTB prevention, conducted at four European hospitals. A log-rank test on Kaplan-Meier curves was used to assess the difference in performance of pessary and progesterone, according to history of PTL-IM or PPROM. Linear regression analysis was used to evaluate significant predictors of gestational age at delivery.

RESULTS

Between 2008 and 2015, 170 women were treated with a pessary and 88 with vaginal progesterone. In women treated with a pessary, rate of sPTB < 34 weeks was 16% in those with a history of PTL-IM and 55% in those with a history of PPROM. In women treated with progesterone, rate of sPTB < 34 weeks was 13% in those with a history of PTL-IM and 21% in those with a history of PPROM. Treatment with a pessary resulted in earlier delivery in women with previous PPROM than in any other subgroup (P < 0.0001). Linear regression analysis showed a clear effect of PPROM history (P < 0.0001), combination of PPROM history and treatment (P = 0.0003) and cervical length (P = 0.0004) on gestational age at birth.

CONCLUSIONS

Cervical pessary may be a less efficacious treatment option for women with previous PPROM; however, these results require prospective validation before change in practice is recommended. Phenotype of previous preterm birth may be an important risk predictor and treatment effect modifier; this information should be reported in future clinical trials. © 2018 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Physiology and Pathophysiology of Steroid Biosynthesis, Transport and Metabolism in the Human Placenta

The steroid hormones progestagens, estrogens, androgens, and glucocorticoids as well as their precursor cholesterol are required for successful establishment and maintenance of pregnancy and proper development of the fetus. The human placenta forms at the interface of maternal and fetal circulation. It participates in biosynthesis and metabolism of steroids as well as their regulated exchange between maternal and fetal compartment. This review outlines the mechanisms of human placental handling of steroid compounds. Cholesterol is transported from mother to offspring involving lipoprotein receptors such as low-density lipoprotein receptor (LDLR) and scavenger receptor class B type I (SRB1) as well as ATP-binding cassette (ABC)-transporters, ABCA1 and ABCG1. Additionally, cholesterol is also a precursor for placental progesterone and estrogen synthesis. Hormone synthesis is predominantly performed by members of the cytochrome P-450 (CYP) enzyme family including CYP11A1 or CYP19A1 and hydroxysteroid dehydrogenases (HSDs) such as 3β-HSD and 17β-HSD. Placental estrogen synthesis requires delivery of sulfate-conjugated precursor molecules from fetal and maternal serum. Placental uptake of these precursors is mediated by members of the solute carrier (SLC) family including sodium-dependent organic anion transporter (SOAT), organic anion transporter 4 (OAT4), and organic anion transporting polypeptide 2B1 (OATP2B1). Maternal-fetal glucocorticoid transport has to be tightly regulated in order to ensure healthy fetal growth and development. For that purpose, the placenta expresses the enzymes 11β-HSD 1 and 2 as well as the transporter ABCB1. This article also summarizes the impact of diverse compounds and diseases on the expression level and activity of the involved transporters, receptors, and metabolizing enzymes and concludes that the regulatory mechanisms changing the physiological to a pathophysiological state are barely explored. The structure and the cellular composition of the human placental barrier are introduced. While steroid production, metabolism and transport in the placental syncytiotrophoblast have been explored for decades, few information is available for the role of placental-fetal endothelial cells in these processes. With regard to placental structure and function, significant differences exist between species. To further decipher physiologic pathways and their pathologic alterations in placental steroid handling, proper model systems are mandatory.

Vaginal progesterone for preventing preterm birth and adverse perinatal outcomes in singleton gestations with a short cervix: a meta-analysis of individual patient data

BACKGROUND

The efficacy of vaginal progesterone for preventing preterm birth and adverse perinatal outcomes in singleton gestations with a short cervix has been questioned after publication of the OPPTIMUM study.

OBJECTIVE

To determine whether vaginal progesterone prevents preterm birth and improves perinatal outcomes in asymptomatic women with a singleton gestation and a midtrimester sonographic short cervix.

STUDY DESIGN

We searched MEDLINE, EMBASE, LILACS, and CINAHL (from their inception to September 2017); Cochrane databases; bibliographies; and conference proceedings for randomized controlled trials comparing vaginal progesterone vs placebo/no treatment in women with a singleton gestation and a midtrimester sonographic cervical length ≤25 mm. This was a systematic review and meta-analysis of individual patient data. The primary outcome was preterm birth <33 weeks of gestation. Secondary outcomes included adverse perinatal outcomes and neurodevelopmental and health outcomes at 2 years of age. Individual patient data were analyzed using a 2-stage approach. Pooled relative risks with 95% confidence intervals were calculated. Quality of evidence was assessed using the GRADE methodology.

RESULTS

Data were available from 974 women (498 allocated to vaginal progesterone, 476 allocated to placebo) with a cervical length ≤25 mm participating in 5 high-quality trials. Vaginal progesterone was associated with a significant reduction in the risk of preterm birth <33 weeks of gestation (relative risk, 0.62; 95% confidence interval, 0.47-0.81; P = .0006; high-quality evidence). Moreover, vaginal progesterone significantly decreased the risk of preterm birth <36, <35, <34, <32, <30, and <28 weeks of gestation; spontaneous preterm birth <33 and <34 weeks of gestation; respiratory distress syndrome; composite neonatal morbidity and mortality; birthweight <1500 and <2500 g; and admission to the neonatal intensive care unit (relative risks from 0.47-0.82; high-quality evidence for all). There were 7 (1.4%) neonatal deaths in the vaginal progesterone group and 15 (3.2%) in the placebo group (relative risk, 0.44; 95% confidence interval, 0.18-1.07; P = .07; low-quality evidence). Maternal adverse events, congenital anomalies, and adverse neurodevelopmental and health outcomes at 2 years of age did not differ between groups.

CONCLUSION

Vaginal progesterone decreases the risk of preterm birth and improves perinatal outcomes in singleton gestations with a midtrimester sonographic short cervix, without any demonstrable deleterious effects on childhood neurodevelopment.

Progesterone inhibits contraction and increases TREK-1 potassium channel expression in late pregnant rat uterus

OBJECTIVE

The aim of this study was to investigate the effect and mechanism by which progesterone regulates uterine contraction in late pregnant rats.

RESULTS

Progesterone caused concentration-dependent relaxation of uterine strips that was enhanced compared with control nontreated uterine strips. Uterine strips incubated with progesterone showed a significant increase in TREK-1 mRNA expression and protein level. TREK-1 inhibitor L-methionine partly reversed uterine relaxation caused by the progesterone, while TREK-1 activator arachidonic acid did not cause significant change in progesterone-induced relaxation.

CONCLUSIONS

Progesterone inhibits uterine contraction and induces uterine relaxation in late pregnancy. The progesterone-induced inhibition of uterine contraction appears to partly involve increased potassium channel TREK-1 expression/activity.

MATERIALS AND METHODS

Uterus from late-pregnant rats (gestational day 19) was isolated, and uterine strips were prepared for isometric contraction measurement. Oxytocin-induced contraction was compared in uterine strips pretreated with different concentration of progesterone. TREK-1 potassium channel inhibitor L-methionine and TREK-1 agonist arachidonic acid were used to determine whether the changes caused by progesterone involve changes in TREK-1 activity. The mRNA and protein expression of TREK-1 in uterine tissues were measured using qPCR and Western blot.

17-alpha hydroxyprogesterone caproate for preterm birth prevention: Where have we been, how did we get here, and where are we going?

Prematurity is a major public health problem in the United States and worldwide. Women with a history of a previous preterm birth are at high risk for recurrence. Progesterone is a key hormone involved in pregnancy maintenance. In general, progesterone is thought to maintain pregnancy through several closely linked mechanisms: (1) promotion of uterine quiescence, (2) inhibition of pro-inflammatory cells, and (3) immunosuppressive action. 17-Alpha hydroxyprogesterone caproate is currently the only medication approved to prevent recurrent preterm birth. The purpose of this review is to discuss the history of 17-alpha hydroxyprogesterone caproate use for recurrent preterm birth prevention, the rationale behind 17-alpha hydroxyprogesterone caproate administration, and current evidence-based indications for 17-alpha hydroxyprogesterone caproate use.

Current concepts in maternal-fetal immunology: Recognition and response to microbial pathogens by decidual stromal cells

Chorioamnionitis is an acute inflammation of the gestational (extraplacental) membranes, most commonly caused by ascending microbial infection. It is associated with adverse neonatal outcomes including preterm birth, neonatal sepsis, and cerebral palsy. The decidua is the outermost layer of the gestational membranes and is likely an important initial site of contact with microbes during ascending infection. However, little is known about how decidual stromal cells (DSCs) respond to microbial threat. Defining the contributions of individual cell types to the complex medley of inflammatory signals during chorioamnionitis could lead to improved interventions aimed at halting this disease. We review available published data supporting the role for DSCs in responding to microbial infection, with a special focus on their expression of pattern recognition receptors and evidence of their responsiveness to pathogen sensing. While DSCs likely play an important role in sensing and responding to infection during the pathogenesis of chorioamnionitis, important knowledge gaps and areas for future research are highlighted.

Prevention of preterm birth with vaginal progesterone or 17-alpha-hydroxyprogesterone caproate: a critical examination of efficacy and safety

Progestogens are the first drugs to demonstrate reproducibly a reduction in the rate of early preterm birth. The efficacy and safety of progestogens are related to individual pharmacologic properties of each drug within this class of medication and characteristics of the population that is treated. The synthetic 17-hydroxyprogesterone caproate and natural progesterone have been studied with the use of a prophylactic strategy in women with a history of preterm birth and in women with a multiple gestation. Evidence from a single large comparative efficacy trial suggests that vaginal natural progesterone is superior to 17-hydroxyprogesterone caproate as a prophylactic treatment in women with a history of mid-trimester preterm birth. Progestogen therapy is indicated for women with this highest risk profile based on evidence from 2 trials. A therapeutic approach based on the identification of a sonographic short cervix has been studied in several phase III trials. Independent phase III trials and an individual patient metaanalysis suggest that vaginal progesterone is efficacious and safe in women with a singleton and a short cervix. Two trials that tested 17-hydroxyprogesterone caproate in women with a short cervix showed no benefit. No consistent benefit for the prophylactic or therapeutic use of progestogens has been demonstrated in larger trials of women whose pregnancies were complicated by a multiple gestation (twins or triplets), preterm labor, or preterm rupture of membranes. Unfortunately, several large randomized trials in multiple gestations have identified harm related to 17-hydroxyprogesterone caproate exposure, and the synthetic drug is contraindicated in this population. The current body of evidence is evaluated by the Grading of Recommendations Assessment, Development, and Evaluation guidelines to derive the strength of recommendation in each of these populations. A large confirmatory trial that is testing 17-hydroxyprogesterone caproate exposure in women with a singleton pregnancy and a history of preterm birth is near completion. Additional study of the efficacy and safety of progestogens is suggested in well-selected populations based on the presence of biomarkers.

Bridging progestogens in pregnancy and pregnancy prevention

Steroid hormones have been in use for more than a half a century as contraceptive agents, and only now are researchers elucidating the biochemical mechanisms of action and non-target effects. Progesterone and synthetic progestins, critical for women's health in the US and internationally, appear to have important effects on immune functioning and other diverse systems. Apart from the contraceptive world is a separate field that is devoted to understanding progesterone in other contexts. Based on research following a development timeline parallel to hormonal contraception, progesterone and 17-hydroxyprogesterone caproate are now administered to prevent preterm birth in high-risk pregnant women. Preterm birth researchers are similarly working to determine the precise biochemical actions and immunological effects of progesterone. Progesterone research in both areas could benefit from increased collaboration and bringing these two bodies of literature together. Progesterone, through actions on various hormone receptors, has lifelong importance in different organ systems and researchers have much to learn about this molecule from the combination of existing literatures, and from future studies that build on this combined knowledge base.

Parturition failure in mice lacking Mamld1

In mice, the onset of parturition is triggered by a rapid decline in circulating progesterone. Progesterone withdrawal occurs as a result of functional luteolysis, which is characterized by an increase in the enzymatic activity of 20α-hydroxysteroid dehydrogenase (20α-HSD) in the corpus luteum and is mediated by the prostaglandin F2α (PGF_2α) signaling. Here, we report that the genetic knockout (KO) of Mamld1, which encodes a putative non-DNA-binding regulator of testicular steroidogenesis, caused defective functional luteolysis and subsequent parturition failure and neonatal deaths. Progesterone receptor inhibition induced the onset of parturition in pregnant KO mice, and MAMLD1 regulated the expression of Akr1c18, the gene encoding 20α-HSD, in cultured cells. Ovaries of KO mice at late gestation were morphologically unremarkable; however, Akr1c18 expression was reduced and expression of its suppressor Stat5b was markedly increased. Several other genes including Prlr, Cyp19a1, Oxtr, and Lgals3 were also dysregulated in the KO ovaries, whereas PGF_2α signaling genes remained unaffected. These results highlight the role of MAMLD1 in labour initiation. MAMLD1 likely participates in functional luteolysis by regulating Stat5b and other genes, independent of the PGF_2α signaling pathway.

Association of 17α-Hydroxyprogesterone Caproate and Risk of Infection

OBJECTIVE

To evaluate whether exposure to 17α-hydroxyprogesterone caproate is associated with the rate of peripartum infection in women who deliver preterm and their neonates.

METHODS

This is a retrospective cohort study of patients who delivered before 37 weeks of gestation at a tertiary care hospital between July 1, 2005, and December 31, 2012. Women in the case group (women exposed to 17α-hydroxyprogesterone caproate) were matched to women in a control group (unexposed patients) by gestational age and delivery date. The primary outcome was a composite infection rate comprising histologic or clinical chorioamnionitis, endometritis, or early-onset neonatal sepsis. To detect a 15% difference in composite infection rate between women exposed to 17α-hydroxyprogesterone caproate and those unexposed (two-tailed α=0.05 and power=80%), 183 patients per group were required. Logistic regression was performed to control for a history of prior spontaneous preterm birth and exposure to betamethasone.

RESULTS

The primary outcome frequency for women exposed to 17α-hydroxyprogesterone caproate was 34.6% (64 patients) compared with 33% (61 patients) in those unexposed (P=.74). There was no significant difference between women exposed to 17α-hydroxyprogesterone caproate and those unexposed in frequency of clinical chorioamnionitis (1.9% compared with 1.1%, P=.66), histologic chorioamnionitis (39.4% compared with 40%, P=.92), or early-onset neonatal sepsis (2.7% compared with 1.1%, P=.28). A total of 7.1% of women exposed to 17α-hydroxyprogesterone caproate developed endometritis compared with 2.7% of those unexposed (P=.05). The adjusted odds ratio for the primary outcome in women exposed to 17α-hydroxyprogesterone caproate was 0.65 (95% confidence interval 0.31-1.38).

CONCLUSION

Exposure to 17α-hydroxyprogesterone caproate does not increase the risk of peripartum infection among women who deliver preterm or their neonates.

LEVEL OF EVIDENCE

II.

17-hydroxyprogesterone caproate significantly improves clinical characteristics of preeclampsia in the reduced uterine perfusion pressure rat model

Preeclampsia is characterized by increased uterine artery resistance index, chronic immune activation, and decreased circulating nitric oxide levels. 17-α-Hydroxyprogesterone caproate (17-OHPC) is a synthetic metabolite of progesterone used for the prevention of recurrent preterm birth. We hypothesized that 17-OHPC could reduce mean arterial pressure by decreasing inflammation, whereas improving vasodilation by increasing nitric oxide bioavailability and uterine artery resistance index during late gestation in the reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. 17-OHPC (3.32 mg/kg) was intraperitoneally administered on gestation day 18 into RUPP rats, carotid catheters inserted, and mean arterial pressure, blood, and tissues were collected on day 19. Mean arterial pressure in normal pregnant (NP; n=13) was 92±2.0 and increased to123±2.0 in RUPP (n=18; P<0.0001), which was improved to 116±1.5 mm Hg in RUPP+17-OHPC (n=10; P<0.05). Circulating CD4+ T cells were 1.19%±1.0% of gated cells in NP (n=7), which increased to 8.52%±2.4% in RUPP rats (n=10; P<0.05) but was reduced to 2.72%±0.87% (n=14; P<0.05) in RUPP+17-OHPC. Circulating nitrate/nitrite was 26.34±3.5 µmol/L in NP (n=12) but was reduced to14.58±3.1 in RUPP rats (n=8; P=0.03) and increased to 22.69±1.62 in RUPP+17-OHPC (n=7; P=0.05). Endothelial nitric oxide synthase expression was 0.65±0.11 AU in NP (n=4), which decreased to 0.33±0.01 in RUPP rats (n=4; P=0.05) but increased to 0.57±0.01 in RUPP+17-OHPC (n=5; P=0.03). Uterine artery resistance index was 0.54±0.02 in NP (n=3), 0.78±0.03 in RUPP (n=4), and 0.63±0.038 in RUPP+17-OHPC (n=8; both P<0.05). Our findings demonstrate that even though modest, lowering blood pressure with 17-OHPC could be a viable treatment option for suppressing inflammation, uterine artery vasoconstriction while improving litter size.

Progesterone supplementation attenuates hypertension and the autoantibody to the angiotensin II type I receptor in response to elevated interleukin-6 during pregnancy

OBJECTIVE

Preeclampsia is a multisystem disorder recognized as hypertension with proteinuria developing >20 weeks' gestation. Preeclampsia is associated with chronic immune activation characterized by increased T and B lymphocytes, cytokines, and antibodies activating the angiotensin II type I receptor (AT1-AA). Hypertension in response to elevated interleukin (IL)-6 during pregnancy occurs with increased renin activity and AT1-AA, and reduced kidney function.

STUDY DESIGN

We aim to determine whether 17-alpha-hydroxyprogesterone caproate (17-OHPC), progesterone, improved inflammatory pathways during elevated IL-6 in pregnant rats. IL-6 (5 ng/d) was infused via miniosmotic pumps into normal pregnant (NP) rats beginning on day 14 of gestation and 17-OHPC (3.32 mg/kg) was diluted in normal saline and injected on day 18. Blood pressure (mean arterial pressure [MAP]) determination and serum collection were performed on day 19 of gestation.

RESULTS

MAP in NP was 100 ± 3 mm Hg, which increased with IL-6 to 112 ± 4 mm Hg (P < .05). Pregnant rats given 17-OHPC alone had a MAP of 99 ± 3 mm Hg and MAP increased to 103 ± 2 mm Hg in IL-6+17-OHPC. AT1-AA was 1.2 ± 0.5 bpm in NP rats, increased to 17 ± 9 bpm with IL-6 infusion but administration of 17-OHPC significantly blunted AT1-AA to 4 ± 0.8 bpm in NP+IL-6+17-OHPC. Total circulating nitrate/nitrite was significantly decreased and placental Ser(1177)-phosporylated-eNOS/eNOS was lowered with IL-6 infusion. Supplementation of 17-OHPC significantly improved placental Ser(1177)-phosporylated-eNOS/eNOS however, circulating nitrate/nitrite was unchanged with 17-OHPC supplementation.

CONCLUSION

This study illustrates that 17-OHPC attenuated hypertension, decreased AT1-AA activity, and improved placental nitric oxide in response to elevated IL-6 during pregnancy and could lend hope to a new potential therapeutic for preeclampsia.

Reduced levels of maternal progesterone during pregnancy increase the risk for allergic airway diseases in females only

Observational as well as experimental studies support that prenatal challenges seemed to be associated with an increased risk for allergic airway diseases in the offspring. However, insights into biomarkers involved in mediating this risk are largely elusive. We here aimed to test the association between endogenous and exogenous factors documented in pregnant women, including psychosocial, endocrine, and life style parameters, and the risk for allergic airway diseases in the children later in life. We further pursued to functionally test identified factors in a mouse model of an allergic airway response. In a prospectively designed pregnancy cohort (n = 409 families), women were recruited between the 4th and 12th week of pregnancy. To investigate an association between exposures during pregnancy and the incidence of allergic airway disease in children between 3 and 5 years of age, multiple logistic regression analyses were applied. Further, in prenatally stressed adult offspring of BALB/c-mated BALB/c female mice, asthma was experimentally induced by ovalbumin (OVA) sensitization. In addition to the prenatal stress challenge, some pregnant females were treated with the progesterone derivative dihydrodydrogesterone (DHD). In humans, we observed that high levels of maternal progesterone in early human pregnancies were associated with a decreased risk for an allergic airway disease (asthma or allergic rhinitis) in daughters (adjusted OR 0.92; 95% confidence interval [CI] 0.84 to 1.00) but not sons (aOR 1.02, 95% CI 0.94-1.10). In mice, prenatal DHD supplementation of stress-challenged dams attenuated prenatal stress-induced airway hyperresponsiveness exclusively in female offspring. Reduced levels of maternal progesterone during pregnancy-which can result from high stress perception-increase the risk for allergic airway diseases in females but not in males. Key messages: Lower maternal progesterone during pregnancy increases the risk for allergic airway disease only in female offspring. Prenatal progesterone supplementation ameliorates airway hyperreactivity in prenatally stressed murine offspring.

Synergy and interactions among biological pathways leading to preterm premature rupture of membranes

Preterm premature rupture of membranes (PPROM) occurs in 1% to 2% of births. Impact of PPROM is greatest in low- and middle-income countries where prematurity-related deaths are most common. Recent investigations identify cytokine and matrix metalloproteinase activation, oxidative stress, and apoptosis as primary pathways to PPROM. These biological processes are initiated by heterogeneous etiologies including infection/inflammation, placental bleeding, uterine overdistention, and genetic polymorphisms. We hypothesize that pathways to PPROM overlap and act synergistically to weaken membranes. We focus our discussion on membrane composition and strength, pathways linking risk factors to membrane weakening, and future research directions to reduce the global burden of PPROM.

Regulation of progesterone signaling during pregnancy: implications for the use of progestins for the prevention of preterm birth

Preterm birth is a major cause of neonatal morbidity and mortality. Progesterone plays a critical role in suppressing the inflammatory signals that would induce parturition prior to term. Progesterone signaling is regulated in a variety of ways during pregnancy. Endocrine production of high levels of progesterone by the placenta ensures the availability of high levels of progesterone throughout pregnancy. Paracrine regulation of progesterone metabolism in target tissues, particularly the myometrium and cervix, also determines the amount of progesterone ligand available. Progesterone metabolism can also lead to the formation of metabolites that contribute to its effects. In particular, 5β-dihydroprogesterone formation by aldo-keto reductase 1D1 appears to play an important role in maintaining uterine quiescence. Progesterone signaling can also be regulated at the receptor level through changes in the relative expression of the nuclear progesterone receptor isoforms, reduced expression of membrane receptors, and changes in the expression levels of coactivators and/or corepressors, including nuclear factor κB. Progesterone and 17α-hydroxyprogesterone caproate (17OH-PC) have recently been shown to reduce preterm births in women with previous preterm birth or shortened cervix. It is important to realize that these two progestins are likely to act in significantly different ways, which will likely influence their efficacy. The structural differences and resistance to metabolism exhibited by 17OH-PC means that it will be unable to activate some of the pathways that progesterone activates, but that it also will not be subject to paracrine inactivation. The fact that progesterone therapy works for maintaining pregnancy in some women, indicates that for those women insufficient levels of progesterone ligand in target tissues is a determining factor in early parturition, despite high levels of circulating progesterone. This article is part of a Special Issue entitled 'Pregnancy and Steroids'.

Loss of progesterone receptor-mediated actions induce preterm cellular and structural remodeling of the cervix and premature birth

A decline in serum progesterone or antagonism of progesterone receptor function results in preterm labor and birth. Whether characteristics of premature remodeling of the cervix after antiprogestins or ovariectomy are similar to that at term was the focus of the present study. Groups of pregnant rats were treated with vehicle, a progesterone receptor antagonist (onapristone or mifepristone), or ovariectomized on day 17 postbreeding. As expected, controls given vehicle delivered at term while rats delivered preterm after progesterone receptor antagonist treatment or ovariectomy. Similar to the cervix before term, the preterm cervix of progesterone receptor antagonist-treated rats was characterized by reduced cell nuclei density, decreased collagen content and structure, as well as a greater presence of macrophages per unit area. Thus, loss of nuclear progesterone receptor-mediated actions promoted structural remodeling of the cervix, increased census of resident macrophages, and preterm birth much like that found in the cervix at term. In contrast to the progesterone receptor antagonist-induced advance in characteristics associated with remodeling, ovariectomy-induced loss of systemic progesterone did not affect hypertrophy, extracellular collagen, or macrophage numbers in the cervix. Thus, the structure and macrophage census in the cervix appear sufficient for premature ripening and birth to occur well before term. With progesterone receptors predominantly localized on cells other than macrophages, the findings suggest that interactions between cells may facilitate the loss of progesterone receptor-mediated actions as part of a final common mechanism that remodels the cervix in certain etiologies of preterm and with parturition at term.

Detection of anti-HLA antibodies in maternal blood in the second trimester to identify patients at risk of antibody-mediated maternal anti-fetal rejection and spontaneous preterm delivery

PROBLEM

Maternal anti-fetal rejection is a mechanism of disease in spontaneous preterm labor. The objective of this study was to determine whether the presence of human leukocyte antigen (HLA) panel-reactive antibodies (PRA) during the second trimester increases the risk of spontaneous preterm delivery.

METHODS OF STUDY

This longitudinal case-control study included pregnant women with spontaneous preterm deliveries (n = 310) and control patients with normal term pregnancies (n = 620), matched for maternal age and gravidity. Maternal plasma samples obtained at 14-16, 16-20, 20-24, and 24-28 weeks of gestation were analyzed for HLA class I and class II PRA positivity using flow cytometry. The fetal HLA genotype and maternal HLA alloantibody epitope were determined for a subset of patients with positive HLA PRA.

RESULTS

(i) Patients with spontaneous preterm delivery were more likely to exhibit HLA class I (adjusted OR = 2.54, P < 0.0001) and class II (adjusted OR = 1.98, P = 0.002) PRA positivity than those delivering at term; (ii) HLA class I PRA positivity for patients with spontaneous preterm delivery between 28 and 34 weeks (adjusted OR = 2.88; P = 0.001) and after 34 weeks of gestation (adjusted OR = 2.53; P < 0.0001) was higher than for those delivering at term; (iii) HLA class II PRA positivity for patients with spontaneous preterm delivery after 34 weeks of gestation was higher than for those delivering at term (adjusted OR = 2.04; P = 0.002); (iv) multiparous women were at a higher risk for HLA class I PRA positivity than nulliparous women (adjusted OR = 0.097, P < 0.0001 for nulliparity); (v) nulliparous women had a higher rate of HLA class I PRA positivity with advancing gestational age (P = 0.001); and (vi) 78% of women whose fetuses were genotyped had alloantibodies specific against fetal HLA class I antigens.

CONCLUSION

Pregnant women with positive HLA class I or class II PRA during the second trimester are at an increased risk of spontaneous preterm delivery due to antibody-mediated maternal anti-fetal rejection.

Progesterone blunts vascular endothelial cell secretion of endothelin-1 in response to placental ischemia

OBJECTIVE

Preeclampsia (PE) is associated with hypertension and elevated endothelin (ET-1), an indicator of endothelial cell activation and dysfunction. Reduction of uteroplacental perfusion (RUPP) in the pregnant rat model of PE is characterized by elevated mean arterial pressure, inflammatory cytokines, and activation of the ET-1 system. We aim to determine whether 17-alpha-hydroxyprogesterone caproate (17-OHPC) or progesterone suppresses these pathways.

STUDY DESIGN

Plasma progesterone was purified from normal pregnant (NP) and PE patients and measured via enzyme-linked immunosorbent assay. Human umbilical vein endothelial cells were exposed to the sera with or without progesterone added and ET-1 was measured. Pregnant rats underwent the RUPP procedure with or without intraperitoneal 17-OHPC. Mean arterial pressure was compared in RUPP vs NP rats. Human umbilical vein endothelial cells were exposed to NP or RUPP sera, with and without progesterone and ET-1 measured.

RESULTS

Progesterone was significantly decreased in PE women compared with NP women. In response to human sera, ET-1 was elevated in PE women compared to NP women, and decreased with addition of progesterone. Mean arterial pressure was significantly elevated in RUPP vs NP rats but was attenuated by 17-OHPC. ET-1 secretion was stimulated significantly by RUPP compared to NP rat sera, but attenuated by progesterone.

CONCLUSION

Circulating progesterone is significantly lower in PE women compared to controls. 17-OHPC attenuates hypertension in response to placental ischemia in RUPP rats. Progesterone blunts vascular ET-1 stimulated at cellular level by sera from PE women or RUPP rats. Decreased circulating progesterone is associated with stimulation of ET-1. 17-OHPC supplementation blunts hypertension and progesterone blunts endothelial cell ET-1 secretion in response to placental ischemia.

Polymorphisms in the fetal progesterone receptor and a calcium-activated potassium channel isoform are associated with preterm birth in an Argentinian population

OBJECTIVE

To investigate genetic etiologies of preterm birth (PTB) in Argentina through evaluation of single-nucleotide polymorphisms (SNPs) in candidate genes and population genetic admixture.

STUDY DESIGN

Genotyping was performed in 389 families. Maternal, paternal and fetal effects were studied separately. Mitochondrial DNA (mtDNA) was sequenced in 50 males and 50 females. Y-chromosome anthropological markers were evaluated in 50 males.

RESULT

Fetal association with PTB was found in the progesterone receptor (PGR, rs1942836; P=0.004). Maternal association with PTB was found in small conductance calcium activated potassium channel isoform 3 (KCNN3, rs883319; P=0.01). Gestational age associated with PTB in PGR rs1942836 at 32-36 weeks (P=0.0004). MtDNA sequencing determined 88 individuals had Amerindian consistent haplogroups. Two individuals had Amerindian Y-chromosome consistent haplotypes.

CONCLUSION

This study replicates single locus fetal associations with PTB in PGR, maternal association in KCNN3, and demonstrates possible effects for divergent racial admixture on PTB.

Residency and activation of myeloid cells during remodeling of the prepartum murine cervix

Remodeling of the cervix is a critical early component of parturition and resembles an inflammatory process. Infiltration and activation of myeloid immune cells along with production of proinflammatory mediators and proteolytic enzymes are hypothesized to regulate cervical remodeling as pregnancy nears term. The present study standardized an approach to assess resident populations of immune cells and phenotypic markers of functional activities related to the mechanism of extracellular matrix degradation in the cervix in preparation for birth. Analysis of cells from the dispersed cervix of mice that were nonpregnant or pregnant (Days 15 and 18 postbreeding) by multicolor flow cytometry indicated increased total cell numbers with pregnancy as well as increased numbers of macrophages, the predominant myeloid cell, by Day 18, the day before birth. The number of activated macrophages involved in matrix metalloproteinase induction (CD147) and signaling for matrix adhesion (CD169) significantly increased by the day before birth. Expression of the adhesion markers CD54 and CD11b by macrophages decreased in the cervix by Day 18 versus that on Day 15 or in nonpregnant mice. The census of cells that expressed the migration marker CD62L was unaffected by pregnancy. The data suggest that remodeling of the cervix at term in mice is associated with recruitment and selective activation of macrophages that promote extracellular matrix degradation. Indices of immigration and activities by macrophages may thus serve as markers for local immune cell activity that is critical for ripening of the cervix in the final common mechanism for parturition at term.

Vaginal progesterone in risk reduction of preterm birth in women with short cervix in the midtrimester of pregnancy

Preterm birth is a major health problem for the neonate, family, country, and society in general. Despite many risk factors being identified for women destined to deliver preterm, short cervical length detected on transvaginal ultrasound is the most plausible, practical and sensitive risk factor for prediction of spontaneous preterm birth. The definition of short cervix has varied in various studies, but most commonly accepted is ≤2.5 cm in the midtrimester of pregnancy, though risk of spontaneous preterm birth (sPTB) increases as the cervical length decreases. Vaginal progesterone, a naturally occurring steroid hormone, is the most bioavailable form of progesterone for uterine and cervical effects with the fewest side effects. Multiple prospective studies have consistently shown its benefits in decreasing sPTB rate in women with asymptomatic midtrimester short cervix. The safety for mother and fetus, and tolerability of vaginal progesterone, particularly the gel form, is also well established. Vaginal progesterone is a minimally invasive intervention that is not painful and is very safe, with reasonable cost where the benefits (even if argued to be small) clearly outweigh the risks. Thus there should be little hesitation for implementation of universal transvaginal cervical length screening and preventive vaginal progesterone treatment for women with short cervix.

Progesterone and preterm birth prevention: translating clinical trials data into clinical practice

OBJECTIVE

We sought to provide evidence-based guidelines for using progestogens for the prevention of preterm birth (PTB).

METHODS

Relevant documents, in particular randomized trials, were identified using PubMed (US National Library of Medicine, 1983 through February 2012) publications, written in English, which evaluate the effectiveness of progestogens for prevention of PTB. Progestogens evaluated were, in particular, vaginal progesterone and 17-alpha-hydroxy-progesterone caproate. Additionally, the Cochrane Library, organizational guidelines, and studies identified through review of the above were utilized to identify relevant articles. Data were evaluated according to population studied, with separate analyses for singleton vs multiple gestations, prior PTB, or short transvaginal ultrasound cervical length (CL), and combinations of these factors. Consistent with US Preventive Task Force suggestions, references were evaluated for quality based on the highest level of evidence, and recommendations were graded.

RESULTS AND RECOMMENDATIONS

Summary of randomized studies indicates that in women with singleton gestations, no prior PTB, and short CL ≤ 20 mm at ≤ 24 weeks, vaginal progesterone, either 90-mg gel or 200-mg suppository, is associated with reduction in PTB and perinatal morbidity and mortality, and can be offered in these cases. The issue of universal CL screening of singleton gestations without prior PTB for the prevention of PTB remains an object of debate. CL screening in singleton gestations without prior PTB cannot yet be universally mandated. Nonetheless, implementation of such a screening strategy can be viewed as reasonable, and can be considered by individual practitioners, following strict guidelines. In singleton gestations with prior PTB 20-36 6/7 weeks, 17-alpha-hydroxy-progesterone caproate 250 mg intramuscularly weekly, preferably starting at 16-20 weeks until 36 weeks, is recommended. In these women with prior PTB, if the transvaginal ultrasound CL shortens to < 25 mm at < 24 weeks, cervical cerclage may be offered. Progestogens have not been associated with prevention of PTB in women who have in the current pregnancy multiple gestations, preterm labor, or preterm premature rupture of membranes. There is insufficient evidence to recommend the use of progestogens in women with any of these risk factors, with or without a short CL.

Vaginal progesterone in women with an asymptomatic sonographic short cervix in the midtrimester decreases preterm delivery and neonatal morbidity: a systematic review and metaanalysis of individual patient data

OBJECTIVE

To determine whether the use of vaginal progesterone in asymptomatic women with a sonographic short cervix (≤ 25 mm) in the midtrimester reduces the risk of preterm birth and improves neonatal morbidity and mortality.

STUDY DESIGN

Individual patient data metaanalysis of randomized controlled trials.

RESULTS

Five trials of high quality were included with a total of 775 women and 827 infants. Treatment with vaginal progesterone was associated with a significant reduction in the rate of preterm birth <33 weeks (relative risk [RR], 0.58; 95% confidence interval [CI], 0.42-0.80), <35 weeks (RR, 0.69; 95% CI, 0.55-0.88), and <28 weeks (RR, 0.50; 95% CI, 0.30-0.81); respiratory distress syndrome (RR, 0.48; 95% CI, 0.30-0.76); composite neonatal morbidity and mortality (RR, 0.57; 95% CI, 0.40-0.81); birthweight <1500 g (RR, 0.55; 95% CI, 0.38-0.80); admission to neonatal intensive care unit (RR, 0.75; 95% CI, 0.59-0.94); and requirement for mechanical ventilation (RR, 0.66; 95% CI, 0.44-0.98). There were no significant differences between the vaginal progesterone and placebo groups in the rate of adverse maternal events or congenital anomalies.

CONCLUSION

Vaginal progesterone administration to asymptomatic women with a sonographic short cervix reduces the risk of preterm birth and neonatal morbidity and mortality.

Progesterone modulates the expression of interleukin-6 in cultured term human uterine cervical fibroblasts

PROBLEM

The preventative value of progesterone in preterm labor has been recently recognized, especially when it is administered via vaginal suppository. This study was undertaken to evaluate the effect of progesterone on interleukin-6 (IL-6) production in human uterine cervical fibroblasts (UCFs) treated with lipopolysaccharides (LPS).

METHOD OF STUDY

Human uterine cervical tissue was obtained at term, prior to the onset of labor, during the scheduled cesarean section or cesarean hysterectomy. Primary UCF cultures were established and confirmed by immunohistochemistry. IL-6 mRNA and protein expressions were examined by reverse-transcription polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.

RESULTS

Lipopolysaccharides stimulation induced a clear time- and dose-dependent increase in IL-6 mRNA and protein levels in UCFs (P < 0.05). Progesterone treatment significantly attenuated LPS-induced increases in IL-6 mRNA and protein expressions in UCFs (P < 0.05). Estrogen exposure had no effect on LPS-induced IL-6 up-regulation and did not modulate the effects of progesterone.

CONCLUSION

Our preliminary results suggest that vaginal progesterone might prevent spontaneous preterm labor through a mechanism involving anti-inflammatory effects on UCFs, particularly suppression of IL-6 production.

Immune stress in late pregnant rats decreases length of gestation and fecundity, and alters later cognitive and affective behaviour of surviving pre-adolescent offspring

Immune challenge during pregnancy is associated with preterm birth and poor perinatal development. The mechanisms of these effects are not known. 5α-Pregnan-3α-ol-20-one (3α,5α-THP), the neuroactive metabolite of progesterone, is critical for neurodevelopment and stress responses, and can influence cognition and affective behaviours. To develop an immune challenge model of preterm birth, pregnant Long-Evans rat dams were administered lipopolysaccharide [LPS; 30 μg/kg/ml, intraperitoneal (IP)], interleukin-1β (IL-1β; 1 μg/rat, IP) or vehicle (0.9% saline, IP) daily on gestational days 17-21. Compared to control treatment, prenatal LPS or IL-1β reduced gestational length and the number of viable pups born. At 28-30 days of age, male and female offspring of mothers exposed to prenatal IL-1β had reduced cognitive performance in the object recognition task compared to controls. In females, but not males, prenatal IL-1β reduced anxiety-like behaviour, indicated by entries to the centre of an open field. In the hippocampus, progesterone turnover to its 5α-reduced metabolites was lower in prenatally exposed IL-1β female, but not in male offspring. IL-1β-exposed males and females had reduced oestradiol content in hippocampus, medial prefrontal cortex and diencephalon compared to controls. Thus, immune stress during late pregnancy reduced gestational length and negatively impacted birth outcomes, hippocampal function and central neurosteroid formation in the offspring.

Progesterone receptor polymorphisms and clinical response to 17-alpha-hydroxyprogesterone caproate

OBJECTIVE

Seventeen-alpha-hydroxyprogesterone caproate (17-OHPC) reduces recurrent preterm birth (PTB). We hypothesized that single nucleotide polymorphisms in the human progesterone receptor (PGR) affect response to 17-OHPC in the prevention of recurrent PTB.

STUDY DESIGN

We conducted secondary analysis of a study of 17-OHPC vs placebo for recurrent PTB prevention. Twenty PGR gene single nucleotide polymorphisms were studied. Multivariable logistic regression assessed for an interaction between PGR genotype and treatment status in modulating the risk of recurrent PTB.

RESULTS

A total of 380 women were included; 253 (66.6%) received 17-OHPC and 127 (33.4%) received placebo. In all, 61.1% of women were African American. Multivariable logistic regression demonstrated significant treatment-genotype interactions (either a beneficial or harmful treatment response) for African Americans delivering<37 weeks' gestation for rs471767 and rs578029, and for Hispanics/Caucasians delivering<37 weeks' gestation for rs500760 and <32 weeks' gestation for rs578029, rs503362, and rs666553.

CONCLUSION

The clinical efficacy and safety of 17-OHPC for recurrent PTB prevention may be altered by PGR gene polymorphisms.