Third birth intention of the childbearing-age population in mainland China and sociodemographic differences: a cross-sectional survey

BACKGROUND: Global fertility declines have become an inevitable trend, and many countries are adopting policies to drive fertility increases. Fertility intention plays an important role in predicting fertility behavior. The Chinese government has recently issued the ‘three-child’ policy, and there is still little research on the third birth intention of the childbearing-age population. Therefore, the aim of this study is to investigate the prevalence and related reasons of third birth intention in the childbearing-age population in mainland China, and analyze the sociodemographic differences. METHOD: A cross-sectional survey was conducted in mainland China from June to July 2021. A total of 15,332 childbearing-age participants responded and completed the Fertility Intention Questionnaire online through the Wenjuanxing Platform. Data were explored and analyzed by SPSS (version 22.0) software. Descriptive statistics were used to describe the current situation and reasons of third birth intention. Binary logistic regression analysis was applied to assess the influencing factors in the sociodemographic level. RESULTS: The mean age of the participants was 32.9 ± 5.94 years. Only 12.2% of participants reported having third birth intention. The subjective norm of having both son and daughter (22.0%) and busy at work (29.2%) accounted for the largest proportion in the reasons of acceptance and rejection, respectively. Age has negative impact on third birth intention (OR = 0.960). Men were 2.209 times more likely to have three children than women (P < 0.001). With the improvement of education and family monthly income, the birth intention shows a downward trend. Compared with Han nationalities, first marriage and city residents, the ethnic minorities, remarriage and rural residents have stronger birth intention (all P < 0.05). And individuals with two existing children are inclined to have the third child (OR = 1.839). CONCLUSION: The third birth intention in the childbearing-age population in China is still low after the announcement of the three-child policy. It is necessary to create a favorable fertility context for childbearing-age group with high level of third birth intention, like younger, male, minority, remarriage, with lower education and family monthly income, living in rural and two existing children. Furthermore, removing barriers for those unintended is also prominent to ensure the impetus of policy. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12889-021-12338-8.