Expert answer: David Geller, pediatrician

An occasional spot of blood in a newborn's diaper is nothing to be alarmed about. There are many possible causes.

• Your baby may have swallowed blood from a cracked nipple during breastfeeding. (The crack may not be obvious and it may take some searching to find it.) This won't hurt your baby and you can continue to breastfeed as your nipple heals.

• The blood may be from a scratch or crack in the skin of your baby's rectum if he or she has had dry, hard, or large bowel movements, but this is rarely a problem for newborns since they haven't started on solid foods and are unlikely to be constipated.

• A female infant may have a little bloody vaginal discharge in her diaper due to the withdrawal of maternal hormones after delivery. This usually stops as the hormones return to normal levels. A male infant may be bleeding a little from a healing circumcision. Finally, diaper rash can lead to some bleeding if it gets severe enough.

Blood in the diaper is a problem only if the bleeding becomes heavy or persistent, or if your baby appears ill, has a high fever, or bruises easily. If you do notice any blood in your baby's diaper, make sure you mention it to your pediatrician to be on the safe side.

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