Mental Floss has a breezy article about how a mother's actions can affect her baby, before birth and afterward.
The article says,
Just because you’ve exited the womb doesn’t mean your mother stops having power over your DNA expression. ... if a female baby rat didn’t get licked enough then her body turned off a series of genes that should have produced certain “mothering” and “love” hormones, like estrogen and oxytocin. Deprived of those, the female rat grew up to exhibit the exact same insufficiently nurturing behavior her mother had shown her—thus continuing on the cycle for another generation. On the other hand, when a baby girl rat got an extraordinary amount of lick-based attention from her mommy, she went on to actually have higher-than-average levels of estrogen and oxytocin.
She's referencing work done by Frances Champagne, Josie Diorio, Shakti Sharma, and Michael J. Meaney showing that how a mother rat treats her babies may directly -- and permanently -- influence the receptivity of oxytocin receptors in their brains.
The researchers said,
"These findings suggest that maternal licking/grooming influences the development of estrogen sensitivity in brain regions that regulate maternal behavior, providing a potential mechanism for the intergenerational transmission of individual differences in maternal behavior."
That's in rats, of course. Oxytocin researchers are still way leery of saying the same thing goes on in humans.