Using data from a population-based medicine use cohort in Xiamen, China, this retrospective cohort study will investigate whether herbal medicines used to prevent miscarriage are associated with increased risk of birth defects.

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.

Inclusion Criteria:

• Pregnancies registered at REPRESENT and underwent live births between January 2013 and December 2018 were included.

Exclusion Criteria:

• (1) those with the first antenatal visit occurring after 20 gestational weeks, (2) those without timing records of the last menstrual period or delivery dates, (3) those with known factors related to birth defects (e.g.,syphilis positive, epilepsy), (4) those prescribed known medications associated with birth defects (e.g.,dezocine, diazepam).

All pregnant women registered at the REPRESENT were enrolled.

Between January 2013 and December 2018, all pregnant women who registered at the REPRESENT in Xiamen was included in this cohort.

Following the policy of Xiamen Health Commission, research institutions could apply for data access by submitting a formal study protocol, subjected to approval by the Xiamen Health and Medical Big Data Center and the Chinese Evidence-based Medicine Center. Ethical review and research registration are mandatory for all studies.