Blood in a Newborn's Stool: What Could It Mean?
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Seeing blood in your newborn's stool is alarming, but the cause is not always serious. A tiny streak of bright red blood may come from a small anal fissure or irritation around the anus. Other possibilities include swallowed maternal blood, cow's-milk protein–related inflammation, infection, or less common intestinal problems.
Because this is a newborn, however, blood in the stool deserves medical attention rather than simply watching it at home. Contact your pediatrician promptly so the cause can be assessed.
- Blood in a newborn's stool should be discussed promptly with the pediatrician.
- A small anal fissure can cause a few streaks of bright red blood.
- Cow's-milk protein–related colitis can cause blood or mucus in an infant's stool.
- Newborns can occasionally swallow maternal blood during delivery or breastfeeding from a bleeding nipple.
- Blood with diarrhea, vomiting, abdominal swelling, fever, poor feeding, or an ill-appearing baby is more concerning.
- Black, tar-like stool after the normal meconium period can represent digested blood and requires medical evaluation.
- Do not automatically change formula or eliminate foods from a breastfeeding parent's diet without discussing the situation with the baby's clinician.
Few diaper changes get a parent's attention faster than seeing something that looks like blood.
Sometimes it is only a thin bright-red streak. Other times blood may be mixed with mucus or loose stool.
There are several possible explanations, ranging from minor irritation to conditions that require prompt treatment.
In a newborn, the safest approach is not to guess. Blood in the stool deserves a call to your pediatrician so the baby's age, appearance, feeding, stool pattern, and examination can all be considered.
What Can Blood in a Newborn's Stool Look Like?
Blood does not always look the same.
A small amount of fresh blood from near the anus is often bright red and may appear as a streak on the outside of the stool or on the diaper.
Blood originating higher in the digestive tract may become darker as it passes through the intestines and can sometimes produce a black, tar-like appearance.
Blood may also appear mixed with mucus or diarrhea depending on the cause.
If possible, take a clear photograph of the diaper before discarding it. That can be very helpful when speaking with your pediatrician.
Could It Be an Anal Fissure?
Yes. A small crack in the skin at the anus is called an anal fissure.
A fissure can produce a few streaks or flecks of bright red blood on the outside of the stool.
The pediatrician may be able to see the small tear during an examination.
Although anal fissures are a common explanation for small amounts of bright red blood, newborn bleeding should still be discussed with the pediatrician rather than assumed to be a fissure.
Could the Blood Have Come From Mom?
Occasionally.
A newborn can swallow a small amount of maternal blood around the time of delivery.
A breastfed baby may also swallow blood if a breastfeeding parent's nipple is cracked and bleeding.
That swallowed blood can later appear in the baby's spit-up or stool.
If there is uncertainty about whether the blood belongs to the baby or was swallowed from the mother, the baby's clinician can help determine the likely source.
The pattern matters.
A tiny streak of bright red blood on an otherwise normal stool in a comfortable, feeding newborn is very different from repeated bloody stools in a baby who is vomiting, distended, lethargic, or feeding poorly.
But because newborns can become ill quickly, I would still want to know about either situation.
Could Cow's-Milk Protein Allergy Cause Blood in the Stool?
Yes. An immune reaction to cow's-milk protein can cause inflammation in an infant's intestinal tract.
One form may cause loose or mucousy stools with streaks of blood. Some babies may also have feeding discomfort, vomiting, eczema, diarrhea, or difficulty gaining weight.
Cow's-milk protein can reach a baby through cow's-milk-based formula. In some breastfed babies, dietary milk protein consumed by the breastfeeding parent may also contribute to symptoms.
However, blood in the stool does not automatically mean milk allergy. The pediatrician should consider the baby's complete history and other possible causes before recommending a major feeding change.
Does My Baby Need Hypoallergenic Formula?
Not necessarily.
If the pediatrician believes cow's-milk protein allergy is the likely cause, a formula-fed baby may be given a trial of an extensively hydrolyzed formula.
Some babies with more significant disease may require an amino-acid-based formula.
That is different from repeatedly changing among standard, “gentle,” or “sensitive” formulas.
Formula selection should be based on the suspected diagnosis rather than simply the presence of one unusual diaper.
Should a Breastfeeding Parent Stop Eating Dairy?
Not automatically.
Breast milk itself remains the preferred feeding for most breastfed babies, and routine maternal dietary restriction is not necessary simply because a baby has one suspicious stool.
If the pediatrician believes the baby has a cow's-milk protein–related condition, a supervised maternal elimination diet may sometimes be recommended.
Before eliminating major food groups, especially for an extended period, discuss the plan with the baby's clinician so both the diagnosis and maternal nutrition are considered.
Could an Infection Cause Bloody Stool?
Yes.
Certain intestinal infections can cause diarrhea containing blood or mucus.
A newborn with bloody diarrhea may also have poor feeding, vomiting, fever, unusual sleepiness, irritability, or other signs of illness.
Because newborns are particularly vulnerable to infection and dehydration, bloody diarrhea requires prompt medical evaluation.
What About Serious Intestinal Problems?
Less commonly, blood in a newborn's stool can occur with more serious intestinal disease.
The concern becomes greater when bleeding occurs along with symptoms such as abdominal swelling, repeated vomiting, green vomiting, significant feeding difficulty, lethargy, temperature abnormalities, or a baby who simply looks sick.
Premature or medically fragile newborns can also develop serious intestinal conditions such as necrotizing enterocolitis, which requires immediate medical care.
The goal is not to frighten parents, but to explain why bloody stool in a newborn should not automatically be dismissed as formula intolerance.
What About Black Stool?
The first stools after birth are normally very dark green to black and sticky. This is called meconium.
That is expected during the first days of life as the newborn transitions to regular stools.
Once meconium has passed and the stools have transitioned, however, a new black, tar-like stool can represent digested blood from higher in the gastrointestinal tract and should be evaluated promptly.
Dark green stool can sometimes look almost black, especially in poor lighting. If you are unsure, save the diaper or take a photograph and contact your pediatrician.
- Take a clear photograph of the diaper.
- If practical, save the diaper for your baby's clinician to inspect.
- Note whether the blood is bright red, dark, mixed throughout the stool, or only on the surface.
- Look for mucus or diarrhea.
- Pay attention to vomiting, especially green vomiting.
- Watch how well your baby is feeding.
- Keep track of wet diapers.
- Check your baby's temperature if the baby seems unwell.
- Contact your pediatrician promptly because the baby is a newborn.
When Should I Call My Pediatrician?
For a newborn, blood in the stool warrants medical guidance even if the amount is small and your baby otherwise seems well.
Be prepared to tell your pediatrician:
- Your baby's exact age.
- Whether your baby was born prematurely.
- How much blood you saw.
- Whether it was bright red, dark, or black.
- Whether the stool contained mucus or was unusually watery.
- Whether this has happened once or repeatedly.
- Whether your baby is breastfeeding, formula feeding, or both.
- Whether your baby is feeding and urinating normally.
- Whether there is vomiting, fever, abdominal swelling, or unusual behavior.
When Is Blood in the Stool an Emergency?
Seek immediate medical evaluation if your newborn has blood in the stool along with:
- A large amount of blood or ongoing bleeding.
- Black, tar-like stool after the meconium period.
- Repeated vomiting.
- Green or bile-stained vomiting.
- A swollen, firm, or unusually tender abdomen.
- Bloody diarrhea.
- Significant feeding difficulty or refusal to feed.
- Marked sleepiness, weakness, poor responsiveness, or difficulty waking.
- Pale, gray, blue, or otherwise abnormal color.
- Signs of significant dehydration.
- A rectal temperature of 100.4°F (38°C) or higher in a baby 3 months old or younger.
- A baby who appears seriously ill.
Do not assume these symptoms are simply caused by milk intolerance or a formula problem.
Frequently Asked Questions
Is a tiny streak of blood in newborn poop always serious?
No. A tiny bright-red streak can come from a minor source such as irritation or an anal fissure. However, because the baby is a newborn, contact your pediatrician rather than assuming the cause is harmless.
Can milk protein allergy cause blood in a newborn's stool?
Yes. Cow's-milk protein–related intestinal inflammation can cause blood or mucus in an infant's stool. Other causes are possible, so the diagnosis should be based on the baby's overall clinical picture rather than blood alone.
Should I immediately change my baby's formula?
No. Contact your pediatrician first. If cow's-milk protein allergy is suspected, your pediatrician can recommend the appropriate type of formula rather than having you repeatedly experiment with different products.
Can a breastfed baby have cow's-milk protein allergy?
Yes. In some infants, dietary cow's-milk protein consumed by the breastfeeding parent may contribute to symptoms. This does not mean the baby is allergic to breast milk itself.
Is black poop normal in a newborn?
Meconium—the first stool after birth—is normally very dark green or black and sticky. After the stools have transitioned away from meconium, a new black, tar-like stool should be evaluated because it can represent digested blood.
Could the red color actually be something other than blood?
Sometimes. Blood can also come from irritated skin around the anus or, in newborn girls, vaginal bleeding related to maternal hormones may appear in the diaper. Your pediatrician can help determine where the blood is actually coming from.
A few bright-red streaks in a diaper can look dramatic, and fortunately the explanation is sometimes minor.
But newborn medicine deserves a lower threshold for evaluation.
Take a picture of the diaper, look at the baby—not just the stool—and call your pediatrician. How your newborn is feeding, breathing, behaving, and looking helps determine how urgently the bleeding needs to be evaluated.
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Join the Parent Club →References & Medical Sources
- American Academy of Pediatrics, HealthyChildren.org. Stools — Blood In
- American Academy of Pediatrics, HealthyChildren.org. Common Conditions in Newborns
- American Academy of Pediatrics, HealthyChildren.org. Abdominal Pain in Infants
- American Academy of Pediatrics, HealthyChildren.org. Red Stools in Children: Common Causes
Related Parent Resources
Find more pediatric guidance about newborn stools, diapers, feeding, digestion, and other common concerns in our Newborn Care Library →
Medical Disclaimer
This article provides general educational information and is not a substitute for medical advice, diagnosis, or treatment from your child's pediatrician or another qualified healthcare professional. Blood in a newborn's stool can have several causes, and the appropriate evaluation depends on the baby's age, examination, feeding, stool pattern, medical history, and associated symptoms. Because newborns and young infants require a lower threshold for medical evaluation, contact your pediatrician promptly if you see blood in your baby's stool. Seek immediate medical care for significant or ongoing bleeding, black tar-like stool after the meconium period, green vomiting, repeated vomiting, abdominal swelling, bloody diarrhea, significant feeding difficulty, marked lethargy, dehydration, abnormal color, a seriously ill-appearing baby, or a rectal temperature of 100.4°F (38°C) or higher in a baby 3 months old or younger.