It is not possible to get pregnant before ovulation begins, according to the National Health Service in England. Ovulation occurs when eggs are released from an ovary. After release, conception is feasible for up to 24 hours. Before ovulation, there is no egg available for fertilization, so pregnancy cannot occur.
On the other hand, sperm can live in the fallopian tubes for up to five days, and if intercourse takes place within five days before ovulation, it is possible for the sperm to survive and fertilize the egg once it is released, explains the American Pregnancy Association. Since every menstrual cycle is unique to the woman, it can be very difficult to predict exactly when ovulation occurs. This makes it difficult for some women to become pregnant, while making it difficult for others to avoid pregnancy.