My sister had a cryptic pregnancy back in 2016 where she had a regular period for 9 months and minimal weight gain (literally did not show because the baby was so far up her back and ribcage), went to the ER for severe abdominal pain, and then left the hospital with my niece a day later. She even took a pregnancy test ~5 months in when she had a bout of morning sickness that lasted, like, a week, and all 3 of them were negative.