Adverse outcomes of Chinese medicines used for threatened miscarriage: a systematic review and meta-analysis.

BACKGROUND Threatened miscarriage is very common in early pregnancy. Chinese medicines have been widely used to prevent spontaneous pregnancy loss. However, the safety of Chinese medicines is still unknown. A systematic review was performed to identify and describe adverse events of Chinese medicines used for threatened miscarriage. METHODS Clinical studies of Chinese medicines for threatened miscarriage were selected. Primary outcomes were occurrence of adverse effects or toxicity of Chinese medicines. Secondary outcomes were failure of treatment and adverse pregnancy and perinatal outcomes. RESULTS Thirty-two relevant articles included 9 randomized controlled trials, 1 quasi-randomized controlled trial and 2 controlled trials comparing Chinese medicines alone or combined medicines with pharmaceuticals and 20 case series with no controls. Sample sizes of each study were generally small. There was variation in Chinese medicine formulation, dosage and duration of treatment. In the pooled randomized controlled trials, dry mouth, constipation and insomnia (2-10%) and intervention failure (3.1-22.3%), diabetic complications (3%), preterm delivery (5%) and neurodevelopmental morbidity (1.8%) were recorded. Meta-analysis demonstrated that intervention failure was significantly lower in the combined Chinese medicines groups than in the Western medicines controls (relative risk = 0.46; 95% confidence interval: 0.30-0.70, I(2)= 0%). No significant differences were found between these groups for adverse effects and toxicity or for adverse pregnancy and perinatal outcomes. CONCLUSIONS Studies varied considerably in design, interventions and outcome measures, therefore conclusive results remain elusive. In the absence of placebo-controlled trials, the safety of Chinese medicines for the treatment of threatened miscarriage is unknown. Rigorous scientific and clinical studies to assess the possible risks of Chinese medicines are needed.