The way that the mother was flirting with her son seemed a bit like an incest wish at times. But she didn't seem jealous of Helen sexually. I found it difficult to figure out whether the mother was encouraging her son to start a family with Helen or not. Or whether she was playing it cool after the relationship had already started. And trying to get the best out of the developing situation in a sly way.

i think the american society is sick in how they treat mothers and fathers and grand parents. how could he drop his mother and grandmother like this and leave, madness.
i mostly will not be able to answer your reply, since marissa mayer hacked my email, no notification

I'm thinking it was pretty obvious.
Swing away, Merrill.Merrill, swing away

I thought the same thing - that mom had a kind of sick love for her son - kissing him on the mouth, being jealous of his girlfriend, and watching his son & girlfriend screw on New Year's.there was a total vibe there besides all that anyway, I thought. I too, was afraid of the baby being a girl & Martha getting rid of it. Like the above poster, I think a baby girl would've just been more competition to Martha, and that is why she was hell-bent on having a grandson - b/c she knew how to make males love her.
"Are you going to your grave with unlived lives in your veins?" ~ The Good Girl

I think alike you, the mother wanted to "breed" a family with her own son!
The first time I watched the movie I was afraid the same thing about the baby being a girl in that case, the newborn had been a new "competitor" to Martha, and she would have rid of the baby and the Paltrow character.
Maybe Martha (in her sick unconscious) wanted some kind of male harem, from a strictly Freudian point of view.