A Cochrane review included 3 studies with a total of 312 subjects. There was no statistically significant difference in the incidence of miscarriage between human chorionic gonadotrophin hCG and 'no hCG' (placebo or no treatment) groups (RR 0.66, 95% CI 0.42 to 1.05; 3 trials, n=303). When hCG and bed rest alone were compared, there was a significant reduction in the risk of miscarriage (RR 0.47; 95% CI 0.27 to 0.82; 2 trials, n=108), however the other trials was of poor methodological quality. There was no report of adverse effects of hCG on mother or baby.
Comment: The quality of evidence is downgraded by study quality (inadequate intention-to-treat adherence in all trials and several shortcomings in one trial) and by imprecise results (limited study size for each comparison).