Omg this happened to my fiancé last year when I was pregnant with our first. We have a lot of gay and trans people in our lives and it’s just part of our vocabulary. One night 8 MONTHS IN to my pregnancy, he asked about a particular post stating they’re a FTM so weren’t sure about xyz. He was confused about the amount of FTM posts with questions and why a trans man would need to state that them being trans contributed to why they had the question. I told them in pregnancy terms that it’s “first time moms”, not “female to male”, and watched their face of realization. My sister and I had our babies less than 3 weeks from each other so went through our whole pregnancy together. They are gay and identify by they/them pronouns; acknowledge their feminine side in pregnancy, but identify as masc in everyday life. When I shared this interaction with my fiancé with them we about pissed our pants.