Fertility Intention to Have a Third Child in China following the Three-Child Policy: A Cross-Sectional Study

China’s three-child policy was implemented in May 2021 to stimulate a rise in fertility levels. However, few previous studies have explored fertility intentions to have a third child and have only focused on childless or one-child populations, resulting in a gap in findings between fertility intention and fertility behavior. Thus, we conducted a nationwide cross-sectional study on 1308 participants with two children. Results showed that only 9.6% of participants reported planning to have a third child and 80.2% of the population had heard of the policy but had no idea of the detailed contents. Participants with two daughters (OR = 3.722, 95% CI = 2.304–6.013) were willing to have one more child. Instrumental values (OR = 1.184, 95% CI = 1.108–1.265) and policy support (OR = 1.190, 95% CI = 1.124–1.259) were the facilitators. Perceived risk (OR = 0.883, 95% CI = 0.839–0.930) and higher educational level (OR = 0.693, 95% CI = 0.533–0.900) were the leading barriers to having one more child. Therefore, the government should deepen parents’ understanding of the “three-child policy” and devise ways of reducing the negative impacts of having a third child to boost the intention to have more children. Our proposed approach can also be used to better understand the reasons for low fertility rates in other countries.