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Days around menstrual period are safe regarding pregnancy
. As her period was due on Saturday, and you had sex on sunday, thus chances of pregnancy were already very low.
As you have given unwanted-72 also within 2 hours, she shouldn't become pregnant due to sex you had on Sunday.
Due to hormonal
imbalance, period can get delayed some times.
Hope you found my response to your query informative and helpful.
With good wishes,
Dr.Chandra Shekhar Sharma