This is amply supported by both statistical patterns, and clinical observation. With nighttime on-demand nursing, pregnancies average 2 1/2 ears apart. More or less.
O'course, I have my own anecdote to throw in, for what it's worth. We kept our newborn son is a blanket-lined Smithfield Ham basket next to the bed, and I could reach over easily and tuck him in next to me if he was restless with the Mama-milk munchies--- we always had a way for me to do nighttime nursing without getting out of bed.
Breast-fed into toddlerhood, and I never ovulated for 2 whole years.
Must have been those industrial-strength lactational hormones. :o)
Lucky you.
Some of us have industrial strength regular hormones.
I nursed each of mine as long as I could, and to the horror of the doctor’s staff, 4 months into the second and third pregnancy. It clearly had no effect in preventing another pregnancy.
I have many friends in the same boat.
Besides, the benefit is about the reduced breast cancer risk. If someone is banking on it as a form of birth control, they need to try something more reliable.