The sex ratio at birth is an issue that has been attracting the attention of demographers, policymakers, and mass media agencies. Therefore, research in this field is in line with societal expectations. The purpose of the study is to analyze changes in the sex ratio at birth in Vinh Long province and explain the causes leading to these changes. This is a qualitative study, so a structured questionnaire was used to interview respondents. The research sample includes 30 people, including 22 family heads, 4 health officials, and 4 population officials. The interview focused on the causes leading to the imbalance in the sex ratio at birth and measures to reduce the gender imbalance. Interview data were analyzed manually by theme. Research results show that from 2005 to 2016, Vinh Long province had a high sex ratio imbalance at birth. This is due to the impact of son preference, the two-child population policy and the advancement of science and technology. From 2017 to 2022, the sex ratio at birth in this locality has almost returned to normal and this thanks to the active implementation of many measures (developing and implementing intervention projects; propagandizing to raise people's awareness and medical staff; praising families who do not choose the sex of the fetus; inspecting and supervising the selection of fetal sex; integrating gender equality content into educational activities at schools; establishing models, clubs that protect/promote girls, etc.). The imbalance in the sex ratio at birth is due to the simultaneous impact of many factors and is created by many stakeholders. The strong involvement of the government, population officials and the correct awareness of people and health officials about gender equality and the consequences of imbalanced sex ratio at birth are the decisive foundation for bringing the sex ratio at birth back to normal.