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It is very less likely to get pregnant by this. So you need not worry about it. Pregnancy occurs after a repeated intercourse; the sperm and egg must meet, fertilise and travel down the Fallopian tubes to implant on the wall of the woman's uterus. Without the introduction of sperm into a woman's vagina, a natural pregnancy cannot be achieved. However, The hands should be thoroughly washed with soap and warm water before and after it Because your finger could be carrying germs like bacteria which can infect your vagina and vice versa if there is infection of vagina you will be carrying it in your hand and spreading it.it is also advisable to use latex gloves which will prevent from infection and contamination.
Hope this helps. Please feel free to ask if you have further queries.