Spacing the children too closely has a whole host of negative consequences, both physical and psychological, for a number of people involved - the child who was conceived too soon after the immediately preceding child was born (physical and psychological consequences), the mother (physical and psychological consequences), and all the older siblings (psychological consequences). Possibly, there are even negative consequences for the father if he gets overwhelmed with having children so frequently, and if his own needs end up being perpetually on the back burner.