Tia most probably can't breast feed her baby because she herself is pretty weak physically. Actually for a first pregnancy and childbirth at such an young age ( I am assuming she is around 20 physically) in a particularly weak body, her simply surviving is nothing short of a miracle and given her age and body's condition I doubt she is actually producing my milk to breast feed. Women don't produce breast milk uniformly at their first pregnancy and it's especially true for young pregnancy, I have seen plenty of cases where very young mothers barely produce milk at all. I think Tia and Cedric are doing well enough for their period.
Also there is a proper reason for who gets their memories back in this world in the later arcs so it doesn't break suspension of disbelief.
Yeah, you are right. It's just something that's been bothering me in media generally. How detached childbirth is depicted. Obviously it makes sense why Tia cannot breastfeed but I still stand by my point that they kind of have nothing to do with the baby.
I'm looking forward to the reason being revealed now. Ty for telling me

Had to read 100+ chapters to catch up and fhew, idk if it was worth it.
I really like that Tia is actually kind of villainous. She really sacrifices people and is kind of a morally grey person. She was a victim of her family but she still killed dozens of people and continues on doing so in this timeline as well. It's kind of sad but I also like it.
The baby is cute but I personally hate how little they have to do with it. Tia, please breastfeed your baby and take care of it yourself. Ik this was not always the case in medieval high society but still. I always find it so unnerving when in media babies are taken away from the mother after being born.
Spoilers
I don't know what to think about Lisia and Cedric getting their memories back. That's always really icky cause... who else? Lawrence appears to have some memories as well, so why not the king? And so on and so forth. Suspension of disbelief only goes this far.
I also disliked the scene in which this is addressed. I was really shocked, it was impactful. But it also was too short. They didn't really talk about tias past deeds and why Cedric chose to be silent about it. He obviously knew she came from the past life. It was always so tragic and it was kind of a let down how easly they resolved it.
It just was not satisfying and I kind of wish he didn't remember and she got to tell him herself