I'm sorry but where I grew up that breast feeding idea was an old wife's tale. That's why alot of children born there are about 12 to 24 months apart.
What's true about breast feeding is that it does help to loose weight and contract uterus into an almost pre pregnancy size.
I believe both of these statements are actually true
Many times breastfeeding delays the return of a menstrual cycle after birth- no ovulation=no pregnancies. But that varies from woman to woman I didn't get my period back until 6 months after birth and then was able to conceive again!