When your baby's too young to communicate, her stool can be one of the best indicators of what's going on in her body. It may be disarming to find gray stool in her diaper, particularly if it's light gray, but this symptom is not necessarily a cause for concern. In some cases, the problem will clear up on its own, although gray bowel movements are occasionally a sign of a more serious medical problem.
Gray stool can be caused by a few factors. In many cases, a baby's stool changes colors because of dyes in his food or a change in diet. Gray stool can occur if a baby begins eating more dairy products, such as when you wean him off of formula and onto dairy milk. This change in color can also be the result of taking antacids, which doctors sometimes prescribe for babies who suffer from severe heartburn, also known as gastroesophageal reflux disease or GERD.
In rare cases, gray stool is a sign that there's a problem with the baby's liver. For instance, this change in color may be caused by a serious childhood liver disease known as biliary atresia. Biliary atresia affects newborns and is usually evident by the second week of life. According to the National Digestive Diseases Information Clearinghouse, biliary atresia occurs in one out of every 10,000 babies. A baby who has this disease has bile ducts that don't work properly, so a dark pigment called bilirubin can't reach the intestines to darken the stool, causing it to be pale gray or even white.
When to Call the Doctor
If your baby has one instance of gray stool but seems otherwise fine, something in her previous meal may have simply caused the change. Call the doctor if her stools remain gray over the course of a day, or if the change in appearance begins just after she begins taking a new medication. Be on the lookout for any other strange symptoms as well. If your newborn appears jaundiced and has dark colored urine in addition to gray stool, these may be signs of a liver problem. Call the doctor immediately.
If your baby's gray stool is caused by diet or medication, her doctor may recommend that you back off on the dairy products for a bit or change her to a different medication, and her stools should soon return to normal. If her problem is caused by her liver, a battery of tests and biopsies may be required to determine the appropriate course of treatment. In the case of biliary atresia, the next step after testing is surgery to confirm the diagnosis and attempt to replace the damaged bile ducts.