I really hate to see a post go unanswered so I'll try. If anyone knows more about this than I, please respond.
The post is confusing to me as I am not totally sure who is getting pregnant, who is transitioning and if they may be one in the same. I think it reads like the wife is currently male and is becoming female and the cis-female spouse is getting pregnant for the last time. I'm going with that one and if I missed, please correct me.
First, talk with a medical doctor.
My understanding is that there are no guarantees how long an individual sperm will remain viable once HRT for a male to female has started. There are no guarantees how long the numbers of viable sperm will remain high enough for a high probability of impregnation. It's all variable. It could be one month it could be ten months or even more. There are too many factors that can come into play for an accurate prediction.
Once pregnant, exposure to the HRT medicines should not happen. First, exposure could occur by direct contact: like touching an estrogen patch. Avoid that. Second, there could be very low level exposure via intercourse. (The T suppressor may be highly protein bound and therefore may bind to the proteins in the seminal fluid and then be transported into the cis-female during ejaculation. There would not be high levels in the fluid but there could be some. I do not know if E would be present in the seminal fluid either.) It is reasonable to avoid that particular exchange of fluid.
Make the baby, start HRT and use a condom.
