sex took place the 25 and period usually starts after 1st of the month, whats the is the chance of pre?

Answer 1

Chances are low if your period is truly due on the 1st. You need a luteal phase (time between ovulation and your period) of at least 10 days to successully conceive. 5 days before your period was due, there would be no egg to fertilize, as they are only good for 24 hours, and you need to ovulate at least 10 days before a period is due, and have sex between 5 days before (since sperm can live 5 days) up until the day after to conceive.

Even when sex is timed perfectly, you only have a 25% chance of conceiving any given month if you are under 30.