Does having sex delays period? if yes then approx. by how many days?

If pregnant 9+ mos.: If you become pregnant then having sex will delay one's period for at least 9 months (usually longer as periods usually don't restart for a few months after delivery, esp. if one breasfeeds). If one does not become pregnant then their period should not be delayed at all. Having a delayed period does not mean one is pregnant but if having unprotected sex it would be a common result!