This is not a simple issue.
I can tell you that personally, at this point in MY life, I shudder to think of myself ever being pregnant. It's not something that can happen for me anyway, but still...the thought of it ever happening, even when I was being sexually active with a man...gave me the creeps.
BUT
Not all ftms, androgynes, and other female-bodied folks feel this way. It is your body and your life. Personally, I'd sit down and think long and hard before committing to the idea of having a child, pre or post transition. If it is important that you have your own biological children, then perhaps you should consider delaying HRT or not doing that at all. There are guys who have kept their female organs and decided to carry their own children. Some are gay and conceive using their partner's sperm. Others are straight and use donor sperm. Some raise their offspring as daddies (Tom Beattie, for example). Others choose to take a more maternal or egalitarian approach (Milk Junkies, for example).
Both of them transitioned prior to getting pregnant and giving birth. Milk Junkies breastfed his son, for crying out loud. I'm positive that there are plenty of ftms and mtfs who have become parents after transition, during transition, prior to transition. Some have bio kids, some adopt, some raise their partner's children from prior relationships.
As for the whole "Men don't have babies" thing....well, typically, they don't. But let's not use that as a justification for why they shouldn't or can't or won't. I do believe that some guys would be willing to carry children if that were an option. I know that some mtfs would love to be able to carry and give birth to their own children as well. Just as many ftms would love to be able to father children. Life ain't fair, but we shouldn't let that limit us when it comes to living our lives.
Just my two cents.