Cách tính chu kỳ kinh nguyệt để tránh thai là biện pháp cổ điển và đã được nhiều người áp dụng từ rất lâu, có hiệu quả khá cao nếu thực hiện đúng cách.
How to calculate the menstrual cycle to avoid pregnancy is the classic measures and has been widely applied for a long time, relatively high effective if done properly.
The way of calculating the menstrual cycle for contraception is classical and has been adopted by many people for a long time, having a fairly high effect if done properly.
The periodic period of cycle to avoid pregnancy is classic measures and a lot of people have been applied for a long time, which is highly effective if doing the right thing.<br>