I would want to comment upon this question somewhat indirectly by focusing on one of the major symbols in this excellent play, which is Mama's plant. Mama is constantly taking care of the plant she has in their room, and admits that this plant does not receive sufficient water or light for its needs. However, crucially, it still flourishes, in spite of its lack of these things. Mama's care is shown to enable the plant to flourish. The parallel between the plant and the children in the play is obvious: Mama cares for them in just the same way, even though it is woefully evident that they are all lacking so much and are being brought up in an environment which makes it difficult for them to flourish.
The children in the play seem to function by making us think about hope and the desire for a better future, that Mama wants so she can plant this plant of hers and let it grow in a more suitable environment. Thus when Ruth talks about getting an abortion, Mama knows that she has to act, even though it might mean upsetting her son. Note what she says:
I--I just seen my family falling apart today... just falling to pieces in front of my eyes... We couldn't of gone on like we was today. We was going backwards 'stead of forwards--talking 'bout killing babies and wishing each other was dead... When it gets like that in life--you just got to do something different, push on out and do something bigger...
Hope is explicitly linked with the children in this play, and Ruth's talk of getting an abortion signals the absolute loss of hope. Mama's act in buying a house signals the return of hope to the family, as they can all begin to look forward to a brighter future where they, like Mama's plant, can finally receive the kind of environment they deserve in which to grow and flourish.