For the previous generation, condom is not common for many couples. So the best
way for them to prevent pregant is to perform 人工輸卵管結紮手術 for the women. However, this is not a 100% safe method, cos the egg is very small and still have
chance to pass through the 結紮ovary tubes and reach the uterus, causing pregant after sex. So you can notice that many families unvoluntarily gave birth to around 3 to 4 childrens in the 70 and 80 generation. Part of the reason will be due to this fact.