I think you are lumping two different poll choices together.
Umah's is the one that advances the Orc questline while Tia's the one that adds her pregnancy as well as the rest of the tribe.
Yes and no as Tia will raise her children in Rumah Chyos said that dealing with the Orcs would have to come first.
I mean it wouldn't be the first time plans change, but setting an order like this would allow the prevention of further story branching, also per logic it would make a whole lot more sence since the Orcs are a threat to the village and providing for the villagers as is is quiet troublesome.
If there were children you'd have to account for main characters from Rumah to not be present dureing the final raid or force the player to take a break until the pregnancy and rest time had passed, you'd also need to setup guards to prevent stray Orcs from slaughtering or abducting the children, while the People are out dealing with the daily neccesarities or planning/conducting the final attack.
Deal with the Orcs first the people of Rumah can be a whole lot more at ease and the tribe would grow in number from liberating the current prisoners.
You also wouldn't have to account to whom has given birth yet dureing the aftermath, etc.