Some women use a method of lactational amenorrhea (LAM) as a means of birth control. (verywellfamily.com)
The Bellagio Consensus provided the scientific basis for defining the conditions under which breastfeeding can be used safely and effectively for birth - spacing purposes, and programmatic guidelines were developed for use of lactational amenorrhea in family planning (1,2). (cdc.gov)
Lactational amenorrhoea method: The evidence is there, why aren't we using it? (babycenter.com)