I read with interest the article by Niu et al  and I wish to make the following comments. First, the overall knowledge of enrolled cases regarding measures of hepatitis B virus (HBV) is shown to be low, which may be related to the study methodology; however, the main limitation in this study was a low response rate that prevents drawing any conclusions.
Second, the global distribution of HBV infection varies significantly between countries, being low in the USA, Western Europe and Canada and high in some parts of Asia and Africa, with higher rates of vertical transmission in these regions. Socioeconomic and political factors, as well as internal wars in some parts of Asia and Africa, have lead to massive migration to areas in the world with low endemicity for HBV . This event has significantly changed the burden of HBV in the USA and other countries with a low prevalence of HBV infection. Therefore, physicians should have knowledge of enrolled cases, including higher-risk and pregnant patients, and in particular people who have immigrated from countries with a high prevalence of HBV infection. Finally, there were no data regarding HBV vaccination in the enrolled cases; if the patients’ HBV vaccination history and their ant-HBs antibody title had been reported, it would have been easy to predict their health precaution in practice and their knowledge regarding hepatitis B in pregnancy .