Safety of Chinese herbal medicines during pregnancy

Miscarriage and infertility have long been public concerns due to the mental and physical suffering they bring to potential parents. There is a strong need for effective and affordable treatments. Chinese herbal medicines (CHMs) have been shown to be effective for preventing miscarriage and treating infertility; however, due to the limited knowledge of their pharmacological mechanisms and unknown potential toxicity, their use has been restricted. This paper reviews 24 clinical trials of CHMs to prevent miscarriage and treat infertility. Most of these studies did not meet the requirements of randomized controlled trials. Even when using quality assessments based on the Newcastle-Ottawa Scale to assess the quality of non-randomized studies, most studies did not meet the requirements. The reviewed papers were evaluated for maternal and embryonic adverse effects, including those in animal experiments. Slight maternal effects were noted, with some reports of severe toxic effects of CHMs for preventing miscarriage and severe adverse maternal effects of CHMs used for infertility. Owing to the poor quality of the randomized controlled clinical trials and the limited number of studies, it is not possible to draw a conclusion. From animal studies, for all three gestational periods, growth delay and congenital anomalies were the most commonly recorded adverse effects. However, baseline toxicological data and detailed mechanisms are still lacking. To gain a better understanding of the potential toxic effects of CHMs, additional high-quality randomized controlled trials should be conducted, and high-throughput in vitro screening method for baseline data should be considered.