So many women come to me when they are trying to become pregnant (we all agree, that 'fall' is such a dreadful term when you are doing everything you can and it's just not happening.)
But many women also come to me once the baby is born, and nothing is like they expected/ hoped for.
When we move from a dyad - two people forming a pair bonding - to a triad - three humans forming a bonding, all sorts of weird and wonderful things can happen.
Dyads are easier, because there is only you and one other to take into account. Threesomes (those kinds as well) are much harder. If we square 2, we get 4. But if we square 3 we get 9. Many more possibilities.
And if the new human is tiny and demanding and frankly unreasonable, it can upset the original dyad catastrophically.
So when you have a baby, lots of things change. Not only the obvious, but also the subtle interactions of the Dyad now rarely exist. The Triad now dominates even if only 2 of them are in the room. So the parent with the baby (most often the mother) can get resentful of the missing parent. And even if both parents are together and the infant is with a trusted sitter, the existence of the third, still impacts the pair, even when not present.
Sometimes just pointing this out can help. They can see the triangulations going on, can catch the dynamics before they start splintering things.
As always, a little self awareness can go a long way...