Socio-economic and cultural factors affected the acceptance of birth control and family planning of hilltribes. This was due to the fact that Lahu and Hmong ethnic groups largely depended on the semi-subsistence production system, and thus household labor was a vital factor for production increase. Furthermore, both ethnic groups put emphasis on the kinship system. The Hmong regard that having many children guarantees that parents are taken care of in their old age, even after death. The two ethnic groups place different value on children’s genders. As a matriarchal society, Lahu prefers daughters to sons because, after marriage, a husband must move in to live with his wife and becomes additional labor for her family. In contrast to the patriarchal society of the Hmong, sons are preferred to daughters because a son is required to look after his family and his aged parents. The more sons one has, the more secure life will become. In addition, a special aspect of Lahu society is that young men and women are relatively free to choose their partners, and getting married or divorced is easily conducted. As a consequence, Lahu women do not like to undergo permanent sterilization. From the investigation, it was revealed that most villagers had not had a correct understanding about birth control. It was also found that children population in every village in the study area outnumbered other age groups. This phenomenon might lead to several negative effects, e.g., the burden child-rearing. For instance, after completing a compulsory education, most children did not have an opportunity to pursue higher education to equip themselves with necessary skills for future vocations. Moreover, there were shortages of arable land to accommodate a population increase.