Another interesting Mexican research paper: A. Halabe Bucay, Endorphins, personality, and inheritance: Establishing the biochemical bases of inheritance. The paper, published by Science Direct, is behind a paywall but it is explained in its basics at Science Daily.
No hard conclussions are provided, as the author claims his aim is more to promote discussion than to estabilish any dogma, but the proposal is that as emotional states appear to affect directly the sperm and egg cells, these could cause epigenetic alterations even before conception that could determine the the expression of the child's genes.
I would argue that as germ cells are rapidly produced and spent, I would actually expect the mother's emotional state to be most important after conception. My two cents anyhow.