Izuku has a secret quirk that can get him or other people pregnant. His quirk turn on without him knowing and like he didn't know he had it and he is the anyone there with denki and they are both in love. And yea that is how he got pregnant.
Also shoutout to
STAI LEGGENDO
Lost and found (kamideku)
Fanfictiondeku and kaminari are great friends until they meet someone who change their lives forever. First story there might be few mistake. Thank you for reading this . ( this doesn't happen in the anime and the art is not mine)