Strengths and Limitations
The advantage of this study is to survey the clinical trial data of pregnant women registered on the clinical trial information platform in China by a systematic, unbiased approach. However, there are three major limitations. First, new drug clinical trials were required by NMPA to register on the drug clinical trial registration and information disclosure platform from September 6, 2013. Therefore, previously registered trials may not be included in the analysis. Second, ChiCTR was established in 2005 by West China Hospital of Sichuan University. In 2007, it was designated by the Ministry of Health to take part on behalf of China in the WHO International Clinical Trials Registry Platform. It is a non-profit academic institution and not a mandatory registry database7. Although some pharmaceutical companies or clinical institutions have conducted clinical trials in pregnant women, they have not yet registered on this information platform. Finally, there are 28,400 trials registered on ChiCTR that are still under review by ethics committee. Some of them were registered even back to 2007, but the registration status has not yet been updated. These are not included in our study because they do not meet the inclusion criteria for our study.