Vaginal progesterone as maintenance treatment after an episode of preterm labour (PROMISE) study: a multicentre, double-blind, randomised, placebo-controlled trial

Progestogen maintenance therapy for prolongation of pregnancy after an episode of preterm labour: A systematic review and meta-analysis

BACKGROUND

Evidence for progestogen maintenance therapy after an episode of preterm labour (PTL) is contradictory.

OBJECTIVES

To assess effectiveness of progestogen maintenance therapy after an episode of PTL.

SEARCH STRATEGY

An electronic search in Central Cochrane, Ovid Embase, Ovid Medline and clinical trial databases was performed.

SELECTION CRITERIA

Randomised controlled trials (RCT) investigating women between 16+0 and 37+0  weeks of gestation with an episode of PTL who were treated with progestogen maintenance therapy compared with a control group.

DATA COLLECTION AND ANALYSIS

Systematic review and meta-analysis were conducted. The primary outcome was latency time in days. Secondary neonatal and maternal outcomes are consistent with the core outcome set for preterm birth studies. Studies were extensively assessed for data trustworthiness (integrity) and risk of bias.

MAIN RESULTS

Thirteen RCT (1722 women) were included. Progestogen maintenance therapy demonstrated a longer latency time of 4.32 days compared with controls (mean difference [MD] 4.32, 95% CI 0.40-8.24) and neonates were born with a higher birthweight (MD 124.25 g, 95% CI 8.99-239.51). No differences were found for other perinatal outcomes. However, when analysing studies with low risk of bias only (five RCT, 591 women), a significantly longer latency time could not be shown (MD 2.44 days; 95% CI -4.55 to 9.42).

CONCLUSIONS

Progestogen maintenance therapy after PTL might have a modest effect on prolongation of latency time. When analysing low risk of bias studies only, this effect was not demonstrated. Validation through further research, preferably by an individual patient data meta-analysis is highly recommended.

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'.

Effectiveness of cervical pessary in women with arrested preterm labor compared to those with asymptomatic cervical shortening

OBJECTIVE

To determine whether the effectiveness of cervical pessary is different in women who experienced cervical shortening after a threatened preterm labor episode compared to those with asymptomatic short cervix.

METHODS

Retrospective study on singleton pregnancies at risk for preterm delivery (PTD) due to cervical length <25 mm before 28 weeks, who were treated with Arabin cervical pessary. Two groups of patients were compared: those who had contractions causing shortening of the cervix, prior to pessary placement, and those who had asymptomatic cervical shortening. Patients carrying a multiple pregnancy and those who underwent iatrogenic PTD were excluded. The primary outcome was the incidence of PTD at different gestational ages. Secondary outcome was the rate of preterm premature rupture of membrane (pPROM). The groups were compared using univariate and multivariate analyses.

RESULTS

115 patients that met the inclusion criteria were identified. Of these, 91 (79%) had asymptomatic cervical shortening, while 24 (21%) had an episode of threatened preterm labor that resolved, and the pessary was placed after the contractions had stopped. The two groups were similar for maternal characteristics, obstetric history, mean gestational age and length of the cervix at the time of pessary insertion. The median gestational age at delivery was significantly lower (36.4 vs 38.0 weeks, p = .02), and the incidence of PTD significantly higher (58.3% vs 30.8%, OR 4.69, 95% CI 1.68-13.1, p < .01) among women who had arrested preterm labor before the pessary was placed compared to the asymptomatic group, after controlling for confounders. The incidence of PTD before 34 and before 32 weeks was also significantly higher in the symptomatic group (p = .02 and p = .005, respectively). Women with asymptomatic cervical shortening had a longer interval between the placement of the pessary and delivery (median 15 weeks). pPROM occurred with a similar incidence in both groups.

CONCLUSIONS

Arabin cervical pessary to prevent preterm delivery seems be less effective in women with a short cervix following an episode of threatened preterm labor than in those with asymptomatic cervical shortening in the second trimester. This finding may help physicians to select patients in which cervical pessary is more likely to be effective, and to improve patient's counseling about this intervention.

Vaginal progesterone for preterm birth prevention in women with arrested preterm labor

OBJECTIVE

We tested the hypothesis that administration of vaginal progesterone in women with arrested preterm labor would result in lower rates of preterm birth <37 weeks compared to placebo.

STUDY DESIGN

We performed a randomized, placebo-controlled trial comparing vaginal progesterone to placebo in women with arrested preterm labor. Our trial included women with a singleton or twin gestation at 24^0/7-33^6/7 weeks' gestation who presented with preterm labor with cervical dilation ≥1 centimeter but remained undelivered. Participants were randomized to receive vaginal progesterone 200 mg daily or an identical placebo. The primary outcome was preterm birth <37 weeks. We performed an updated systematic review and meta-analysis of clinical trials, including our results. We searched MEDLINE, EMBASE, CINHAL, Scopus, the Cochrane Database of Systematic Reviews, and ClinicalTrials.gov using the key terms to identify relevant trials. The risk of bias was appraised using the Cochrane risk-of-bias tool. Data were synthesized using random-effects models. Heterogeneity was assessed using Higgins I².

RESULTS

The randomized trial was prematurely terminated due to slow recruitment. There were 18 women randomized to receive vaginal progesterone who had complete follow-up data and 18 women in the placebo group. The risk of preterm birth <37 weeks was not significantly different in the groups (RR 1.10, 95% CI 0.63-1.19). Secondary outcomes were also similar. Thirteen trials with 1658 women (835 in the vaginal progesterone and 823 in the control groups) were included in the meta-analysis. Risk of preterm birth <37 weeks was similar in women who received progesterone and those in the control group (pooled RR 1.06, 95% CI 0.83-1.35). Latency was significantly longer among women with arrested preterm labor who received vaginal progesterone (weighted mean difference: 9.2 d, 95% CI 3.2-15.1), but further analysis showed that prolonged latency was only observed in the subgroup of studies that were not placebo-controlled.

CONCLUSIONS

This randomized controlled trial and meta-analysis do not support the use of vaginal progesterone for the prevention of preterm birth in women who present in preterm labor.

Guideline No. 398: Progesterone for Prevention of Spontaneous Preterm Birth

OBJECTIVES

To assess the benefits and risks of progesterone therapy for women at increased risk of spontaneous preterm birth (SPB) and to make recommendations for the use of progesterone to reduce the risk of SPB and improve postnatal outcomes.

OPTIONS

To administer or withhold progesterone therapy for women deemed to be at high risk of SPB.

OUTCOMES

Preterm birth, neonatal morbidity and mortality, and postnatal outcomes including neurodevelopmental outcomes.

INTENDED USERS

Maternity care providers, including midwives, family physicians, and obstetricians.

TARGET POPULATION

Pregnant women at increased risk of SPB.

EVIDENCE

Medline, PubMed, EMBASE, and the Cochrane Library were searched from inception to October 2018 for medical subject heading (MeSH) terms and keywords related to pregnancy, preterm birth, previous preterm birth, short cervix, uterine anomalies, cervical conization, neonatal morbidity and mortality, and postnatal outcomes. This document represents an abstraction of the evidence rather than a methodological review.

VALIDATION METHODS

This guideline was reviewed by the Maternal-Fetal Medicine Committee of the Society of Obstetricians and Gynaecologists of Canada (SOGC) and approved by the SOGC Board of Directors.

BENEFITS, HARMS, AND/OR COSTS

Therapy with progesterone significantly reduces the risk of SPB in a subpopulation of women at increased risk. Although this therapy entails a cost to the woman in addition to the discomfort associated with its use, no other adverse effects to the mother or the baby have been identified.

SUMMARY STATEMENTS (GRADE RATINGS IN PARENTHESES)

RECOMMENDATIONS (GRADE RATINGS IN PARENTHESES).

Vaginal Progesterone Supplementation in the Management of Preterm Labor: A Randomized Controlled Trial

OBJECTIVES

The primary objective in this study was to evaluate the effects of vaginal progesterone supplementation for the prolongation of the latency period in preterm labor. The secondary objectives were to evaluate gestational age at delivery, rates of preterm birth less than 34 and 37 weeks, obstetric outcomes, maternal compliance with medication use, and side effects.

METHODS

A randomized controlled, unblinded trial was performed. Ninety women with preterm labor occurring at 24 to 34 weeks were either randomized to a vaginal progesterone group (44 women) receiving tocolytic and antenatal corticosteroids treatment combined with vaginal micronized progesterone (400 mg everyday) or to the no-progesterone group (46 women) receiving tocolytic and antenatal corticosteroids treatment only.

RESULTS

Latency periods were more prolonged in the vaginal progesterone group than in the no-progesterone group (32.8 ± 18.7 vs. 25.8 ± 22.7 days, p = 0.045). Gestational age at delivery in the vaginal progesterone group was also higher than in the no-progesterone group (37 vs. 35 weeks, p = 0.027). There were significant reduction rates of preterm birth less than 34 weeks (13.6% vs. 39.1%, p = 0.012), low birth weight (29.5% vs. 50%, p = 0.048), neonatal respiratory distress syndrome (13.6% vs. 37%, p = 0.021), and neonatal intensive care unit admission (6.8% vs. 28.3%, p = 0.017).

CONCLUSIONS

Combined treatment with vaginal progesterone 400 mg could prolong the latency period in preterm labor when compared with no progesterone.

Oral dydrogesterone as an adjunctive therapy in the management of preterm labor: a randomized, double blinded, placebo-controlled trial

BACKGROUND

Preterm birth is a major challenge in obstetric and perinatal care. It is the leading cause of neonatal death. The primary aim of this study was to evaluate the efficacy of oral dydrogesterone on latency period in managing preterm labor. The secondary aims were to evaluate the gestational age at delivery, percentage of preterm delivery before 34 weeks and 37 weeks, time to recurrent uterine contraction, pregnancy outcomes, neonatal outcomes, compliance and side effects.

METHODS

This was a randomized, double blinded, placebo-controlled trial. Forty-eight pregnant women with preterm labor, singleton pregnancy, and gestational age of 24-34 weeks were enrolled into the study. The study group received 10 mg of oral dydrogesterone three times per day and the control group received placebo. All pregnant women received standard treatment with tocolytic and antenatal corticosteroids.

RESULTS

The median latency periods were not significantly different between the dydrogesterone group (27.5 days) and placebo group (34 days, p = 0.45). Additionally, there were no differences in the gestational age at delivery, percentage of preterm delivery before 34 weeks and 37 weeks, pregnancy outcomes, neonatal outcomes, compliance and side effects. However, the time to the recurrence of uterine contractions in participants that had recurrent preterm labor was longer in the dydrogesterone group than in the placebo group (30.6 ± 12.3 vs 13.7 ± 5.0 days, p = 0.01).

CONCLUSIONS

Adjunctive treatment with 30 mg of oral dydrogesterone could not prolong latency period in preterm labor when compared to placebo.

TRIAL REGISTRATION

ClinicalTrials.gov (Clinical trials registration: NCT03935152 , registered on May 2,2019).

Maintenance tocolysis: a reappraisal of clinical evidence

INTRODUCTION

Maintenance tocolysis, mostly defined as the continuation of tocolytic treatment beyond 48 h, remains a matter of debate. There is no sufficient evidence from randomized controlled trials, that maintenance tocolysis is able to prolong pregnancy significantly and to reduce severe neonatal morbidity and mortality. Hence, it is not recommended in current guidelines. On the contrary, maintenance tocolysis is commonly used in clinical practice and subject of current clinical-scientific investigations.

TOCOLYTICS FOR MAINTENANCE TREATMENT

None of the conventional tocolytics (beta-sympathomimetics, calcium-channel blockers, magnesium, cyclooxygenase inhibitors, and oxytocin receptor antagonists) have proven to be appropriate for maintenance treatment. Progesterone and 17-α-hydroxyprogesterone caproate have shown promising results in low-quality randomized trials, but not in high-quality studies.

DISCUSSION

Basically, the value of studies regarding maintenance tocolysis is limited by a considerable heterogeneity, its mostly low quality, significant differences in methodology as well as the inadequate statistical power due to the small number of women studied. So far, maintenance tocolysis is a case-by-case decision outweighing the benefits and harms of tocolytic treatment.

Cervical pessary for preventing preterm birth in twin pregnancies with maternal short cervix after an episode of threatened preterm labor: randomised controlled trial

BACKGROUND

No intervention has proved effective to date in reducing the spontaneous preterm birth rate in twin pregnancies following an episode of threatened preterm labor and with a short cervix remaining. This study was designed to ascertain whether cervical pessaries are useful in preventing spontaneous preterm birth in women with twin pregnancies and a short cervix remaining after a threatened preterm labor episode.

STUDY DESIGN

This open, randomized, controlled trial was conducted in 132 pregnant women who had not delivered 48 hours after a threatened preterm labor episode and had a short cervix remaining (≤20 mm between 24⁰ and 29⁶ weeks and ≤10 mm between 30⁰ and 33⁶ weeks). Patients were randomly assigned to cervical pessary (n = 67) or routine management (n = 65). The primary outcome was the spontaneous preterm birth rate before 34 weeks. Spontaneous preterm birth before 28 and 37 weeks and neonatal morbidity and mortality were also evaluated in an intention-to-treat analysis.

RESULTS

Significant differences were observed in the spontaneous preterm birth rate before 34 weeks between the pessary and routine management groups (11 of 67 [16.4%] in the pessary group vs 21 of 65 [32.3%] in the control group; relative risk, 0.51 [confidence interval, 0.27-0.97]; P = .03). No significant differences were observed in the preterm birth rate < 28 weeks or < 37 weeks between groups. The pessary group less frequently required readmission for new threatened preterm labor episodes (4 of 67 [5.6%] vs 14 of 65 [21.5%]; relative risk, 0.28 [confidence interval, 0.10-0.80]; P = .009). Significant reduction was observed in the number of neonates weighing less than 2500 g (17.9% [24 of 134] vs 70.8% [92 of 130]; relative risk, 0.25 [confidence interval, 0.15-0.43]; P < .0001).

CONCLUSION

Pessary use did significantly lower the spontaneous preterm birth rate before 34 weeks in twin pregnancies with maternal short cervix remaining after a threatened preterm labor episode. Pessary use also reduced the threatened preterm labor recurrence and neonates' weight less than 2500 g.

Progesterone - Effective for Tocolysis and Maintenance Treatment After Arrested Preterm Labour?: Critical Analysis of the Evidence

Numerous experimental studies indicate that natural progesterone, through various mechanisms, exerts an inhibitory effect on uterine contractility and sensitises the myometrium for tocolytics. It was therefore appropriate to investigate the possible benefits of oral/vaginal progesterone and the synthetic progesterone derivative 17-α-hydroxyprogesterone caproate, applied intramuscularly, in clinical studies on primary tocolysis, additively to established tocolytics ("adjunctive tocolysis") and as maintenance treatment after successful tocolysis in cases of threatened preterm birth. Three studies with a small number of cases do not yield any sufficient evidence for recommending progesterone/17-α-hydroxyprogesterone caproate as primary tocolysis in women with preterm labour. There is also no evidence that progesterone or 17-α-hydroxyprogesterone caproate combined with commonly used tocolytics leads to a prolongation of pregnancy and a significant decrease in the rate of preterm birth. The data on the use of progesterone as maintenance treatment is controversial. While randomised, controlled studies with low quality showed promising results, studies with high quality did not reveal any significant differences with regard to the rate of preterm birth < 37 weeks of gestation, the latency period until delivery and in the neonatal outcome between progesterone/17-α-hydroxyprogesterone caproate and placebo or no treatment. Significant differences in the methodology, the inclusion and outcome criteria, the mode of application and the dosages of the substances as well as the inadequate statistical power as a result of low numbers of cases make interpretation and comparability of the studies difficult. Therefore, well-designed randomised, placebo-controlled, double-blind studies with uniform primary outcome criteria are needed in order to clarify whether progesterone and via which route of administration and at which dosage is of clinical benefit for patients with manifest preterm contractions and as maintenance treatment after arrested preterm labour.

Cervical pessary to reduce preterm birth <34 weeks of gestation after an episode of preterm labor and a short cervix: a randomized controlled trial

BACKGROUND

To date, no intervention has proved effective in reducing the spontaneous preterm birth rate in singleton pregnancies following an episode of threatened preterm labor and short cervix remaining.

OBJECTIVE

This study was designed to ascertain whether cervical pessaries could be useful in preventing spontaneous preterm birth in women with singleton pregnancies and a short cervix after a threatened preterm labor episode.

STUDY DESIGN

This open randomized controlled trial was conducted in 357 pregnant women (between 24⁰-33⁶ weeks) who had not delivered 48 hours after a threatened preterm labor episode and had a short cervix remaining (≤25 mm at 24⁰-29⁶ weeks; ≤15 mm at 30⁰-33⁶ weeks). Patients were randomly assigned to cervical pessary (179) or routine management (178). The primary outcome was the spontaneous preterm birth rate <34 weeks. Spontaneous preterm birth <28 and 37 weeks and neonatal morbidity and mortality were also evaluated in an intention-to-treat analysis.

RESULTS

No significant differences between the pessary and routine management groups were observed in the spontaneous preterm birth rate <34 weeks (19/177 [10.7%] in the pessary group vs 24/175 [13.7%] in the control group; relative risk, 0.78; 95% confidence interval, 0.45-1.38). Spontaneous preterm birth <37 weeks occurred less frequently in the pessary group (26/175 [14.7%] vs 44/175 [25.1%]; relative risk, 0.58; 95% confidence interval, 0.38-0.90; P = .01). Preterm premature rupture of membranes rate was significantly lower in pessary carriers (4/177 [2.3%] vs 14/175 [8.0%]; relative risk, 0.28; 95% confidence interval, 0.09-0.84; P = .01). The pessary group less frequently required readmission for new threatened preterm labor episodes (8/177 [4.5%] vs 35/175 [20.0%]; relative risk, 0.23; 95% confidence interval, 0.11-0.47; P < .0001). No serious adverse maternal events occurred; neonatal morbidity and mortality were similar in both groups.

CONCLUSION

Pessary use did not significantly lower the spontaneous preterm birth rate <34 weeks in women with a short cervix remaining after a threatened preterm labor episode but did significantly reduce the spontaneous preterm birth rate <37 weeks, threatened preterm labor recurrence, and the preterm premature rupture of membranes rate.

Progesterone as a tocolytic agent for preterm labor: a systematic review

PURPOSE OF REVIEW

Tocolytic agents have been used for over 60 years in the fight against preterm labor, which ultimately can lead to preterm birth. Currently, clinicians can choose from a variety of drug classes to achieve the primary goal of delaying delivery by 48 h, thereby allowing time for administration of corticosteroids for fetal lung maturity, and if appropriate, starting magnesium sulfate for fetal neuroprotection. However, there are currently no known therapies to maintain the tocolytic effect beyond those initial 48 h.

RECENT FINDINGS

Progesterone, which has been used in the prevention of preterm birth for over 10 years, has long been known to have the effect of uterine quiescence. It was first studied as a tocolytic agent in the 1960s. In the last several years, more studies have been done that suggest a potential use for maintenance tocolysis after the successful arrest of preterm labor. Although the studies are conflicting, the meta-analyses on progesterone show some promise in different outcomes of delayed delivery, reduced incidence of preterm birth, and reduced neonatal morbidity.

SUMMARY

Progesterone is currently the most promising agent for maintenance tocolysis. Although further trials are certainly needed, this is an exciting advancement in the realm of tocolysis.

Use of progesterone supplement therapy for prevention of preterm birth: review of literatures

Preterm birth (PTB) is one of the most common complications during pregnancy and it primarily accounts for neonatal mortality and numerous morbidities including long-term sequelae including cerebral palsy and developmental disability. The most effective treatment of PTB is prediction and prevention of its risks. Risk factors of PTB include history of PTB, short cervical length (CL), multiple pregnancies, ethnicity, smoking, uterine anomaly and history of curettage or cervical conization. Among these risk factors, history of PTB, and short CL are the most important predictive factors. Progesterone supplement therapy is one of the few proven effective methods to prevent PTB in women with history of spontaneous PTB and in women with short CL. There are 2 types of progesterone therapy currently used for prevention of PTB: weekly intramuscular injection of 17-alpha hydroxyprogesterone caproate and daily administration of natural micronized progesterone vaginal gel, vaginal suppository, or oral capsule. However, the efficacy of progesterone therapy to prevent PTB may vary depending on the administration route, form, dose of progesterone and indications for the treatment. This review aims to summarize the efficacy and safety of progesterone supplement therapy on prevention of PTB according to different indication, type, route, and dose of progesterone, based on the results of recent randomized trials and meta-analysis.

Progestogens for Maintenance Tocolysis in Women With a Short Cervix: A Randomized Controlled Trial

OBJECTIVE

To assess the efficacy of progestogens for maintenance tocolysis in women undelivered after their first preterm labor episode.

METHODS

Women with singleton pregnancies between 22 0/7 and 31 6/7 weeks of gestation with arrested preterm labor and a cervical length 25 mm or less at hospital discharge were eligible. Patients with a previous preterm birth were excluded. In a randomized controlled trial conducted in five university hospitals, women were randomized to receive vaginal progesterone (200 mg per day) or intramuscular 17α-hydroxyprogesterone caproate (341 mg per week) or to an observation groups (control group). The primary outcome was the proportion of women with preterm birth at less than 37 weeks of gestation. A sample size of 160 per group (n=480) was planned to compare vaginal progesterone and 17α-hydroxyprogesterone caproate groups with those in the control group. The sample size estimation was based on the hypothesis that the risk of experiencing preterm birth in the control group would be 30% and that 17α-hydroxyprogesterone caproate or progesterone would decrease this risk to 15%. A P value of <.025 was defined as statistically significant. At planned interim analysis (n=254), the trial was stopped for futility.

RESULTS

Between July 2010 and June 2015, 257 women were eligible and 254 were subsequently randomly assigned to vaginal progesterone (n=86), 17α-hydroxyprogesterone caproate (n=87), or observation (n=81). Nineteen (8%) were excluded from the analysis because they either dropped out or information was missing, leaving 235 women available for analysis. Demographic characteristics were similar across groups. The preterm birth rate did not differ significantly between groups: 23% in the 17α-hydroxyprogesterone caproate group, 39% in the vaginal progesterone group, and 22% in the women in the control group (P=.949 for 17α-hydroxyprogesterone caproate compared with the women in the control group and P=.027 for vaginal progesterone compared with women in the control group).

CONCLUSION

The use of progestogens for maintenance tocolysis in women with a short cervix did not reduce the rate of preterm birth.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT01178788.