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Background Miscarriage, defined as the spontaneous loss of a pregnancy before 24 weeks' gestation, is common with approximately 25% of women experiencing a miscarriage in their lifetime. An estimated 15% of pregnancies end in miscarriage. Miscarriage can lead to serious morbidity, including haemorrhage, infection, and even death, particularly in settings without adequate healthcare provision. Early miscarriages occur during the first 14 weeks of pregnancy, and can be managed expectantly, medically or surgically. However, there is uncertainty about the relative effectiveness and risks of each option. Objectives To estimate the relative effectiveness and safety profiles for the different management methods for early miscarriage, and to provide rankings of the available methods according to their effectiveness, safety, and side-effect profile using a network meta-analysis. Search methods We searched the Cochrane Pregnancy and Childbirth's Trials Register (9 February 2021), ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (12 February 2021), and reference lists of retrieved studies. Selection criteria We included all randomised controlled trials assessing the effectiveness or safety of methods for miscarriage management. Early miscarriage was defined as less than or equal to 14 weeks of gestation, and included missed and incomplete miscarriage. Management of late miscarriages after 14 weeks of gestation (often referred to as intrauterine fetal deaths) was not eligible for inclusion in the review. Cluster- and quasi-randomised trials were eligible for inclusion. Randomised trials published only as abstracts were eligible if sufficient information could be retrieved. We excluded non-randomised trials. Data collection and analysis At least three review authors independently assessed the trials for inclusion and risk of bias, extracted data and checked them for accuracy. We estimated the relative effects and rankings for the primary outcomes of complete miscarriage and composite outcome of death or serious complications. The certainty of evidence was assessed using GRADE. Relative effects for the primary outcomes are reported subgrouped by the type of miscarriage (incomplete and missed miscarriage). We also performed pairwise meta-analyses and network meta-analysis to determine the relative effects and rankings of all available methods. Main results Our network meta-analysis included 78 randomised trials involving 17,795 women from 37 countries. Most trials (71/78) were conducted in hospital settings and included women with missed or incomplete miscarriage. Across 158 trial arms, the following methods were used: 51 trial arms (33%) used misoprostol; 50 (32%) used suction aspiration; 26 (16%) used expectant management or placebo; 17 (11%) used dilatation and curettage; 11 (6%) used mifepristone plus misoprostol; and three (2%) used suction aspiration plus cervical preparation. Of these 78 studies, 71 (90%) contributed data in a usable form for meta-analysis. Complete miscarriage Based on the relative effects from the network meta-analysis of 59 trials (12,591 women), we found that five methods may be more effective than expectant management or placebo for achieving a complete miscarriage: · suction aspiration after cervical preparation (risk ratio (RR) 2.12, 95% confidence interval (CI) 1.41 to 3.20, low-certainty evidence), · dilatation and curettage (RR 1.49, 95% CI 1.26 to 1.75, low-certainty evidence), · suction aspiration (RR 1.44, 95% CI 1.29 to 1.62, low-certainty evidence), · mifepristone plus misoprostol (RR 1.42, 95% CI 1.22 to 1.66, moderate-certainty evidence), · misoprostol (RR 1.30, 95% CI 1.16 to 1.46, low-certainty evidence). The highest ranked surgical method was suction aspiration after cervical preparation. The highest ranked non-surgical treatment was mifepristone plus misoprostol. All surgical methods were ranked higher than medical methods, which in turn ranked above expectant management or placebo. Composite outcome of death and serious complications Based on the relative effects from the network meta-analysis of 35 trials (8161 women), we found that four methods with available data were compatible with a wide range of treatment effects compared with expectant management or placebo: · dilatation and curettage (RR 0.43, 95% CI 0.17 to 1.06, low-certainty evidence), · suction aspiration (RR 0.55, 95% CI 0.23 to 1.32, low-certainty evidence), · misoprostol (RR 0.50, 95% CI 0.22 to 1.15, low-certainty evidence), · mifepristone plus misoprostol (RR 0.76, 95% CI 0.31 to 1.84, low-certainty evidence). Importantly, no deaths were reported in these studies, thus this composite outcome was entirely composed of serious complications, including blood transfusions, uterine perforations, hysterectomies, and intensive care unit admissions. Expectant management and placebo ranked the lowest when compared with alternative treatment interventions. Subgroup analyses by type of miscarriage (missed or incomplete) agreed with the overall analysis in that surgical methods were the most effective treatment, followed by medical methods and then expectant management or placebo, but there are possible subgroup differences in the effectiveness of the available methods. AUTHORS' CONCLUSIONS: Based on relative effects from the network meta-analysis, all surgical and medical methods for managing a miscarriage may be more effective than expectant management or placebo. Surgical methods were ranked highest for managing a miscarriage, followed by medical methods, which in turn ranked above expectant management or placebo. Expectant management or placebo had the highest chance of serious complications, including the need for unplanned or emergency surgery. A subgroup analysis showed that surgical and medical methods may be more beneficial in women with missed miscarriage compared to women with incomplete miscarriage. Since type of miscarriage (missed and incomplete) appears to be a source of inconsistency and heterogeneity within these data, we acknowledge that the main network meta-analysis may be unreliable. However, we plan to explore this further in future updates and consider the primary analysis as separate networks for missed and incomplete miscarriage.

BACKGROUND: Miscarriage, defined as the spontaneous loss of a pregnancy before 24 weeks’ gestation, is common with approximately 25% of women experiencing a miscarriage in their lifetime, and 15% to 20% of pregnancies ending in a miscarriage. Progesterone has an important role in maintaining a pregnancy, and supplementation with different progestogens in early pregnancy has been attempted to rescue a pregnancy in women with early pregnancy bleeding (threatened miscarriage), and to prevent miscarriages in asymptomatic women who have a history of three or more previous miscarriages (recurrent miscarriage). OBJECTIVES: To estimate the relative effectiveness and safety profiles for the different progestogen treatments for threatened and recurrent miscarriage, and provide rankings of the available treatments according to their effectiveness, safety, and side‐effect profile. SEARCH METHODS: We searched the following databases up to 15 December 2020: Cochrane Central Register of Controlled Trials, Ovid MEDLINE(R), ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP), and reference lists of retrieved studies. SELECTION CRITERIA: We included all randomised controlled trials assessing the effectiveness or safety of progestogen treatment for the prevention of miscarriage. Cluster‐randomised trials were eligible for inclusion. Randomised trials published only as abstracts were eligible if sufficient information could be retrieved. We excluded quasi‐ and non‐randomised trials. DATA COLLECTION AND ANALYSIS: At least two review authors independently assessed the trials for inclusion and risk of bias, extracted data and checked them for accuracy. We performed pairwise meta‐analyses and indirect comparisons, where possible, to determine the relative effects of all available treatments, but due to the limited number of included studies only direct or indirect comparisons were possible. We estimated the relative effects for the primary outcome of live birth and the secondary outcomes including miscarriage (< 24 weeks of gestation), preterm birth (< 37 weeks of gestation), stillbirth, ectopic pregnancy, congenital abnormalities, and adverse drug events. Relative effects for all outcomes are reported separately by the type of miscarriage (threatened and recurrent miscarriage). We used the GRADE approach to assess the certainty of evidence. MAIN RESULTS: Our meta‐analysis included seven randomised trials involving 5,682 women, and all provided data for meta‐analysis. All trials were conducted in hospital settings. Across seven trials (14 treatment arms), the following treatments were used: three arms (21%) used vaginal micronized progesterone; three arms (21%) used dydrogesterone; one arm (7%) used oral micronized progesterone; one arm (7%) used 17‐α‐hydroxyprogesterone, and six arms (43%) used placebo. Women with threatened miscarriage Based on the relative effects from the pairwise meta‐analysis, vaginal micronized progesterone (two trials, 4090 women, risk ratio (RR) 1.03, 95% confidence interval (CI) 1.00 to 1.07, high‐certainty evidence), and dydrogesterone (one trial, 406 women, RR 0.98, 95% CI 0.89 to 1.07, moderate‐certainty evidence) probably make little or no difference to the live birth rate when compared with placebo for women with threatened miscarriage. No data are available to assess the effectiveness of 17‐α‐hydroxyprogesterone or oral micronized progesterone for the outcome of live birth in women with threatened miscarriage. The pre‐specified subgroup analysis by number of previous miscarriages is only possible for vaginal micronized progesterone in women with threatened miscarriage. In women with no previous miscarriages and early pregnancy bleeding, there is probably little or no improvement in the live birth rate (RR 0.99, 95% CI 0.95 to 1.04, high‐certainty evidence) when treated with vaginal micronized progesterone compared to placebo. However, for women with one or more previous miscarriages and early pregnancy bleeding, vaginal micronized progesterone increases the live birth rate compared to placebo (RR 1.08, 95% CI 1.02 to 1.15, high‐certainty evidence). Women with recurrent miscarriage Based on the results from one trial (826 women) vaginal micronized progesterone (RR 1.04, 95% CI 0.95 to 1.15, high‐certainty evidence) probably makes little or no difference to the live birth rate when compared with placebo for women with recurrent miscarriage. The evidence for dydrogesterone compared with placebo for women with recurrent miscarriage is of very low‐certainty evidence, therefore the effects remain unclear. No data are available to assess the effectiveness of 17‐α‐hydroxyprogesterone or oral micronized progesterone for the outcome of live birth in women with recurrent miscarriage. Additional outcomes All progestogen treatments have a wide range of effects on the other pre‐specified outcomes (miscarriage (< 24 weeks of gestation), preterm birth (< 37 weeks of gestation), stillbirth, ectopic pregnancy) in comparison to placebo for both threatened and recurrent miscarriage. Moderate‐ and low‐certainty evidence with a wide range of effects suggests that there is probably no difference in congenital abnormalities and adverse drug events with vaginal micronized progesterone for threatened (congenital abnormalities RR 1.00, 95% CI 0.68 to 1.46, moderate‐certainty evidence; adverse drug events RR 1.07 95% CI 0.81 to 1.39, moderate‐certainty evidence) or recurrent miscarriage (congenital abnormalities 0.75, 95% CI 0.31 to 1.85, low‐certainty evidence; adverse drug events RR 1.46, 95% CI 0.93 to 2.29, moderate‐certainty evidence) compared with placebo. There are limited data and very low‐certainty evidence on congenital abnormalities and adverse drug events for the other progestogens. AUTHORS' CONCLUSIONS: The overall available evidence suggests that progestogens probably make little or no difference to live birth rate for women with threatened or recurrent miscarriage. However, vaginal micronized progesterone may increase the live birth rate for women with a history of one or more previous miscarriages and early pregnancy bleeding, with likely no difference in adverse events. There is still uncertainty over the effectiveness and safety of alternative progestogen treatments for threatened and recurrent miscarriage.