Can one get pregnant after having unprotected sex on the last day of her period

Hello Anon

Thank you for writing.

There is no true "safe" time to have sex since a cycle can become unpredictable suddenly, even if a woman's cycle is generally very reliable.
If a woman has sex on the last day of her cycle, she may be at risk for pregnancy if she has a short cycle, because sperm can last in her body up to days.
We can't advise whether or not to take EC - that's up to the woman involved but we can say that there is a minor risk of pregnancy if she does not.
Best,
Susan