Whether you can get pregnant or not if you have intercourse just once a month depends mainly on what time of the day the intercourse takes place. If you have intercourse right after your period has cleared, you are not likely to get pregnant. If you have intercourse in the middle of your period, that is, during ovulation, the chances of getting pregnant are very high and it is very easy to get pregnant. If you have intercourse before you are about to have your period, the chances of getting pregnant are very low. Depending on when you have intercourse, having intercourse on any day of the entire ovulation period can lead to pregnancy, although having intercourse once is likely to result in pregnancy if it happens to coincide with ovulation, and it is not likely to result in pregnancy if you have intercourse during a non-ovulatory period.