Hepatitis B has been a serious public health problem in Hainan for a long time. In 1992, the Chinese national HBV seroprevalence survey found that the HBsAg seroprevalence of the population in Hainan was 16.54%, ranking first in China . The seroprevalence level of HBsAg of 9.51% in this study of the childbearing age women in Hainan is higher than the 7.18% found among the overall population of China ; it is also higher than those women of childbearing age in Jiangsu province, China (6.71%) , pregnant women in Catalonia, Spain (1.2%)  and in Greece (1.16%) ; but lower than women of childbearing age in Madagascar (13.6%) . Overall, the high positive rate of HBsAg among rural women of childbearing age in Hainan highlights the need for public health workers and government to come up with preventive measures of reducing the prevalence of HBsAg among women of childbearing age.
This study showed that HBsAg carrier rate was significantly related with age of the rural women. The highest prevalence of HBsAg is in the age group of 30 ~ 34 years, followed by the age group of 25 ~ 29 and 20~24 years, which are at the peak period of pregnancy. Similar results were found in other studies conducted in Turkey , Lorestan, West of Iran , Nicobarese tribe  and Mexico which was a country of low endemicity for HBV . Mother to child transmission is an important transmission route for HBV; 30% ~50% of chronic carriers of HBV in China can be attributed to maternal-infantile transmission . Furthermore, Ranger-Rogez S  pointed out that if the mother was HBsAg positive, plus HBeAg and DNA positive, the risk for the neonate to be infected was about 90%, and this child would become a chronic carrier in 80%~90% case. The prevention and control of HBV infection among women of childbearing age should therefore, be a priority of public health intervention in order to reduce the transmission of HBV from mother to child.
Our study found that the HBsAg positivity rate among women of Li ethnic group was higher than Han and other ethnic groups. Li people are the largest ethnic minorities in Hainan, with 14.73% of all Hainan population. Li people are the aboriginal peoples of Hainan, with a history of thousands of years. There are 1.25 million people of Li ethnic in China, and 1.11 million of them are from Hainan. However, epidemiological data on the different prevalence rate of HBsAg between Li women and women from the other ethnic background in China are limited, only a few studies have been conducted in counties and cities of Hainan province [27, 28]; and their results are consistent with this study. As regards to few epidemiological studies conducted on the subject among Li people, the cause of high prevalence rate of HBsAg among this group is still unknown. Despite this, there are two possible reasons. Firstly, Li people have a different dietary habit and lifestyle from Han people, for instance, communal eating and living together is commonly practiced among Li people . An experiment done by Bancroft WH et al., demonstrated that human saliva can serve as a vehicle for the transmission of hepatitis B virus. Another study has also shown that HBV may occur in households with a persistent carrier probably via saliva or open wounds, although it is less efficient than sexual or perinatal transmission . Secondly, there may be HBV susceptibility genes among Li people; for ethnicity might play a role in the different prevalence rates of the HBsAg . This calls for molecular epidemiological studies to verify this notion.
In this study, the HBsAg prevalence was strongly correlated with low education level and low family income. The prevalence of HBsAg in women with junior high or lower education level was higher than in those with higher level, which is consistent with previous studies conducted in general population samples [12, 23]. People with a higher level of education tend to efficiently utilize health services like vaccination, health education, high quality dentistry services, etc. The prevalence of HBsAg in individuals with a lower family monthly income (<2000RMB) was significantly higher than those with a higher income level (≥2000RMB). This result is similar to other studies’ reported that positive HBsAg status was less likely to occur among people with high socioeconomic status compared to those with low or middle socioeconomic status [32, 33]. Poor and crowded living conditions, which are common in rural areas, can facilitate horizontal transmission between siblings, especially with a high rate of HBsAg carriers, as described elsewhere . The finding of our study indicated that HBsAg positivity rate among rural women of childbearing age in Hainan province was geographically influenced. The positivity rate tended to be higher in the western region followed by the central and the east region, which was opposite to the economic level distribution pattern . This finding agrees with the finding in our study, that economic status was a major risk factor of HBsAg prevalence.
Another most common factor observed was having an HBsAg-positive family member. Previous researches found similar results deduced from the general population [13, 29, 35]. Our results demonstrated that no previous history of vaccination significantly increased risk of HBsAg infection. This illustrates the need and importance of expanding and re-intensifying immunization program with extension to adults.
Rural women of childbearing age with tattoo and body piercing were significantly higher than those with no tattoo or body piercing. In a study by Zhang et al. in Canada, tattooing and body piercing increased the risk of HBsAg significantly. In Mexico with low endemicity for HBV also have found tattooing was risk factor detected with a high frequency . But Komas et al. described that tattooing or body piercing did not increase the risk. This difference might be due to the different ethnic study population. In our study, all the subjects were female, which may be biased, as females were more likely to pierce than men. Having a vaginoscopy history and a history of induced abortion among women of childbearing age were two critical risk factors for HBsAg positivity which were different from other population. The prevalence of HBsAg among women with a history of vaginoscopy and induced abortion was significantly higher than those without. We do not know whether this results from confounding bias or other reasons, since there are no related studies to support these findings. However, this illustrates the need to pay seriously attention to promote safe sex behaviours among women of childbearing age to maintain good health of the reproductive system.
In this study, marital status was not a related factor to HBsAg, although some studies have shown marriage and heterosexual relationship to be related to HBsAg positivity [12, 38]. In a study by Roman et al. in Mexico illuminated that marital status had denoted an OR of 1.92 in single or divorced pregnant women and 7.4 in widows among general population. These differences are probably due to cultural differences in each population. Like many other studies [12, 24, 37, 39], this study showed that a history of blood transfusion, surgery, dental surgery and endoscopy was not a risk factor for HBsAg. Although a study by Zali et al. reported that a history of major surgery was associated to HBV. This probably indicates that there is a good surgery and nursing care environment in Hainan.
This study had three limitations. First, our study was a cross sectional design which was therefore, difficult to establish causal relations. Nevertheless, the findings provide important demographic insights on HBsAg positivity among rural women of childbearing age in Hainan province. Another limitation is that HBV infection can be transmitted efficiently through sexual intercourse and the role of sexual behavior in HBsAg seropositivity was not assessed. Thirdly, this study did not include urban women, who happen to have different economic levels, living surroundings, medical environment and conditions and etcetera from rural population which has impact on HBsAg seroprevalence. Therefore, we plan to conduct a sero-epidemiological survey of urban women in Hainan in the future.