Before the woman can become pregnant, she needs to ovulate and after ovulation the egg meets a sperm cell which fertilizes the egg. It also means that there are actually quite a few days during a cycle when the woman can get pregnant.
Sex before ovulation
Sperm cells can live for 5-6 days in the woman's fallopian tubes, and therefore it increases the chance of pregnancy if you have sex already before ovulation. When you know you are ovulating - For example, because you have a positive ovulation test. Read more about when to start testing for ovulation here: When to test for ovulation? – Gravidtid Or because the temperature method has shown it. Read more about the temperature method here: What is the temperature method BBT and how does it work? – Gravidtid Then it is recommended to have sex on the same day and the following day to increase the chance of pregnancy. Before the test becomes completely positive, it is also good to have sex, as the sperm cells can live inside the woman for up to 5 days, and thereby increases the chance that the egg will be able to meet a sperm cell before it perishes after approx. 24 hours.
If you don't like using ovulation tests, then having sex 2-3 times a week is also a good rule of thumb. Then you can almost be sure to hit ovulation and then just cross your fingers and hope that one of the sperm succeeds in fertilizing the egg.