OBJECTIVES: To determine the efficacy and the safety of progestogens in the treatment of threatened miscarriage.

SEARCH METHODS: We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (8 August 2017) and reference lists of retrieved trials.

SELECTION CRITERIA: Randomised, quasi-randomised or cluster-randomised controlled trials, that compared progestogen with placebo, no treatment or any other treatment for the treatment of threatened miscarriage in women carrying singleton pregnancy.

DATA COLLECTION AND ANALYSIS: At least two review authors assessed the trials for inclusion in the review, assessed trial quality and extracted the data and graded the body of evidence.

MAIN RESULTS: We included seven trials (involving 696 participants) in this update of the review. The included trials were conducted in different countries, covering the full spectrum of the World Bank's economic classification, which enhances the applicability of evidence drawn from this review. Two trials were conducted in Germany and Italy which are high-income countries, while four trials were conducted in upper-middle income countries; two in Iran, one in Malaysia and the fourth in Turkey, and the seventh trial was conducted in Jordan, which is a lower-middle income country. In six trials all the participants met the inclusion criteria and in the seventh study, we included in the meta-analysis only the subgroup of participants who met the inclusion criteria. We assessed the body of evidence for the main outcomes using the GRADE tool and the quality of the evidence ranged from very low to moderate. Downgrading of evidence was based on the high risk of bias in six of the seven included trials and a small number of events and wide confidence intervals for some outcomes.Treatment of miscarriage with progestogens compared to placebo or no treatment probably reduces the risk of miscarriage; (risk ratio (RR) 0.64, 95% confidence interval (CI) 0.47 to 0.87; 7 trials; 696 women; moderate-quality evidence). Treatment with oral progestogen compared to no treatment also probably reduces the miscarriage rate (RR 0.57, 95% CI 0.38 to 0.85; 3 trials; 408 women; moderate-quality evidence). However treatment with vaginal progesterone compared to placebo, probably has little or no effect in reducing the miscarriage rate (RR 0.75, 95% CI 0.47 to 1.21; 4 trials; 288 women; moderate-quality evidence). The subgroup interaction test indicated no difference according to route of administration between the oral and vaginal subgroups of progesterone.Treatment of preterm birth with the use of progestogens compared to placebo or no treatment may have little or no effect in reducing the rate of preterm birth (RR 0.86, 95% CI 0.52 to 1.44; 5 trials; 588 women; low-quality evidence).We are uncertain if treatment of threatened miscarriage with progestogens compared to placebo or no treatment has any effect on the rate of congenital abnormalities because the quality of the evidence is very low (RR 0.70, 95% CI 0.10 to 4.82; 2 trials; 337 infants; very-low quality evidence).

METHODS: This is a retrospective observational study involving 58 pregnancies from 1st January 2013 to 31st December 2019. Inclusion criteria were previous mid-trimester miscarriage and/or preterm birth, previous cervical surgery or short cervical length on routine sonogram. The demographic data, characteristics of each pregnancy and details of outcomes and management were described.

RESULTS: The majority of women were Malay with mean age and body mass index of 32.9 ± 4.2 years and 27.1 ± 6.3 kg/m2 respectively. The most frequent indications for Arabin pessary insertion were previous mid-trimester miscarriage (46.4%) and early preterm birth (17.2%). A total of 73.4% of these women had the pessary inserted electively at a mean cervical length of 31.6 ± 9.1 mm at median gestation of 15.0 weeks. They were managed as outpatient (56.9%), inpatient (24.1%) or mixed (19.0%) with combination of progestogen (81.0%) and 53.4% received antenatal corticosteroids. Spontaneous preterm birth at or more than 34 weeks gestation occurred in 74.1% with birthweight at or more than 2000 g (82.4%). Despite cervical funneling in 12 women (20.7%), 66.7% delivered at or later than 34 weeks gestation and 2 (16.7%) resulted in miscarriage.

CONCLUSIONS: Insertion of the Arabin pessary is beneficial to prevent spontaneous preterm birth in pregnant women who are at high risk. In particular, early insertion and close monitoring allows the best possible outcomes.