Miscarriage Preventing Herbal Medicines and the Risk of Birth Defects: a Population-based Cohort Study

Herbal medicines have a long history of use for pregnant women both in China and around the world. However, the safety of herbal medicines used at the early gestation is often questioned regarding their impact on offspring. Therefore, the aim of this study is to investigate whether miscarriage preventing herbal medicines associated with increased risk of birth defects.

A large medication use cohort will be developed by linking a population-based pregnancy registry (i.e., REPRESENT) and a population-based pharmacy database, which documented all prescriptions at both outpatients and inpatients from conception to delivery. This cohort will include herbal medicines formula which were granted approval by the Chinese National Medical Products Administration.

Using data from this cohort, the investigators will investigate the prevalence of the use of herbal medicine formulas and prescription patterns at the first trimester. This study will then investigate the association between miscarriage preventing herbal medicines and the risk of birth defects. A propensity score matching (PSM) based Poisson regression will be used to estimate the relative risk. To ensure the robustness of the results investigators will perform several sensitivity analyses and negative control analyses, such as restricting the population to women with singleton pregnancies, excluding individuals who had undergone in vitro fertilization (IVF), and considering those women who were prescribed herbal medicines during the middle and late stages of pregnancy as the negative exposure control group.