Many pregnant women are nohagos to go to the mikvah when they enter their ninth month, as a segulah for an easier labor and delivery. There are also women who are trying to become pregnant (but so far not successful at reaching that aim), who go into the mikvah on their leil tevilah, as the next tvilah after a ninth month pregnant woman has gone in. It takes some coordination of mikvah nights with the pregnant woman making herself available bedavka on the other woman’s leil tevilah, but the ladies are very accommodating. I do not know the origins of these two segulos, but I can tell you for a fact that a woman went into the mikvah after my pregnant daughter-in-law, and she became pregnant with her first child almost immediately. Both of them had boys. Whether or not this has any validity, it is an accepted segulah in my neighborhood.
Another segulah in my neighborhood, is the collective baking of challah by 40 women, in order to be mafrish the challah and make the bracha in the zechus of a cholah.