Most maternity hospitals really do only allow one person in the delivery room - it's not a whim, it's a safety rule for mom and baby. A husband in the delivery room won't get in the doctors' way if he just stands in the corner and stays out of it, but a lot of women in labor say that having a close person nearby calms them down. If you have to choose between your husband and your mom, husbands are more often the choice - he's more needed during the actual labor, while mom can help before and after. Try to work it out with the maternity hospital about your mom being there at least in the prenatal room, if it doesn't work out for the delivery room itself.