The socio-culture factors affecting birth rate with my explanation are:

1. Illiteracy: It is one of the most common problems from the time of our grandparents which is still prevalent to this day. This has led to the problem of people not understanding the difference between a large family and a small family. Remember if the people of the country are educated then only we can develop a country.
2. The importance of son: Well well, do I even need to say anything about this people have been sexist in our country for most of our time and this is also the reason they choose son over daughter which had led to the most couples trying for another baby until and unless a son is born which is affecting birth rate.
3. Family structure: Now when I say family structure most of you may not understand. But what I am trying to say here is that if you are from a joint family you are mostly expected to marry at a young age and have conception at an early age which also means they will have no idea about family planning which heavily affects the birth rate
4. Polygamy/Polyandry: When a man is married to one woman it is called polygamy and vice versa. First of all, this is a social evil and secondly, it's illegal (so don't do this kids). Also, this evil leads to an increase in population.
5. Poor status of women: We know that Nepal is a male-dominated society. Still, the condition of women is not good. They are doing all of the housework like cooking, cleaning, washing, rearing their children. Most of the women sit in their house and do all this work. So believe me this has led them to bear a child forcefully which also affects the birth rate.