Things can go wrong unexpectedly during pregnancy. For example I just hosted a party on the weekend after Halloween and one of my friends was totally fine and having a good time, then suddenly in the middle of the night after the party she woke up in excruciating pain and bleeding heavily so went to the ER. It turns out she had an ectopic pregnancy, and was able to get the treatment she needed and is still alive instead of bleeding to death in the parking lot of the hospital.