The biggest factor is whether or not you are
breastfeeding. You can get pregnant while
breastfeeding; however, if your baby is less than six months old, you have not had a period, and your baby is taking only breast milk and not other foods or formula, breastfeeding can be around 98% effective as birth control. After six months, or if you have had a period, or if your baby is eating other foods or formula, breastfeeding cannot be relied on as a method of birth control.