It's very uncommon, but it is possible since having your period doesn’t predict when you will release an egg which has to be present for sperm to begin the process of conception. Additionally, since sperm can live inside your uterus for up to 5 days, if you release an egg during these 5 days you run the risk of getting pregnant. Due to the unpredictability of your cycle, if you want to avoid pregnancy it’s important to use contraception even when you are menstruating.
It's very uncommon, but it is possible since having your period doesn’t predict when you will release an egg which has to be present for sperm to begin the process of conception. Additionally, since sperm can live inside your uterus for up to 5 days, if you release an egg during these 5 days you run the risk of getting pregnant. Due to the unpredictability of your cycle, if you want to avoid pregnancy it’s important to use contraception even when you are menstruating.