As Atom notes, discussion about periods, child birth and sex are very common among women and girls and being part of those conversations we might expect to have a response, including saying nothing at all. The latter answer doesn't do much for making better friends and reminds me of how I acted as a trans person in denial for so many years. I tried to blend in with the guys but didn't feel like one. When I could have told the truth I said stuff like "gee how about that hot car or those Mets or something I thought was manly or I said nothing at all. I had fewer friends, partly because I was hiding the truth; I am not one of you guys!
To me this is the crux of going stealth or focusing on passing, or blending in so no one will know our past. Very personal decisions I respect and sometimes a volatile conversation here.
It is my opinion that unless we have a perfect memory and a flawless presentation we may trip up and reveal our past. We can avoid those difficult questions, deflecting and distracting as we go. Another option is to consider being discreet but telling the truth while still sharing only as much as one is comfortable with.
I love being part of the girls club and talking about sex and reproductive health and never again want to hide who I am. I have found that other women now trust me more and I am not seen as some predatory male. I want those confidences to continue and believe having something to hide puts that at risk.
I recall being so elated, years ago, that I seemed to be passing and a guy was sort of hitting on me at a dinner. As we walked to the hotel we started talking about high school traumas and I talked about going to an all boys military high school. Game over because I told the truth or a lesson I learned about starting with the truth?
We do have and make choices that may even be life altering. How do we want to live?