Aims: To investigate the characteristics of prescriptions during pregnancy from Beijing Prescription Comment System from 2016 to 2018. Methods: Data was extracted and selected in the system with key words according to inclusion criteria. We examined patterns and assessed risks with FDA category categorization. Factors associated to D/X, C, N/A categories were explored through multivariate logistic regression. We re-classified the drugs with Briggs categorization of B, C, D, N/A categories. Results: From 5,446,561 prescriptions of Beijing Prescription Comment System, 647 varieties of chemical or biomedical drugs with 112,566 prescriptions were finally included. The prescriptions majorly distributed on patients from 25 to 35 years (68.17%), in 1st and 2nd trimesters (75.05%). Drugs in FDA category were followed by B (23.83%), C (13.37%), X (6.17%), A (3.26%), D (1.7%), while 51.68% not available. In D/X categories, estrogens, assisted reproductive drugs and imaging testing drugs were most. Within X category, prescriptions showed an increase in women under 25 years from 216 to 2018. In drugs of D/X categories, gestational week under 12 weeks (OR=3.259, 95%CI, 1.441-7.37) matters most among risk factors of specialized hospitals, gestational age between 30 and 35, and non-obstetrics and gynecology departments. Under Briggs categorization, FDA category C contains more risk drugs in animal or human tests (74.25%) according to Briggs categorization. Conclusions: This research explored exposure of pregnant women to potential risk drugs by FDA category and Briggs categorization. Main characteristics and risk factors revealed by this study should be monitored in the ongoing studies on pregnancy drug safety.