Data analysis
All relevant trials are merged, checked and screened to exclude unqualified items. Microsoft EXCEL was used for descriptive statistics of the data, and then the trials were classified according to the following specific therapeutic areas (rank by quantity): anesthesia/analgesia; anti-infectiousagents (including treatment and prevention); endocrine diseases (mainly gestational diabetes mellitus (GDM) and thyroid diseases); postpartum hemorrhage (PPH) (only include the trials where subjects took the investigational drugs before giving birth); inducers; premature delivery/delivery; preeclampsia and pregnancy-induced hypertension (PIH); miscarriage and recurrent miscarriage; dietary supplement to improve pregnancy outcome; vomiting. The total number of trials in each database was compared with the number of trials relevant to pregnancy, and the comparison was expressed in percentage and original number. Analysis by region includes the location of the initiator and study sites. If the trial was conducted by different sites in the same region, it falls in the cumulative calculation for that region. Our analysis focused on three aspects of pregnancy trials: the overall finding of initial trials conducted between 2013 and 2020 (number, drug type, and study design); the therapeutic areas; and the geographical distribution of all clinical trial institutes and industry funds.