The first stool a baby has is a thick, green, gooey mess called meconium. (For the record, meconium consists of all the stuff babies swallow during his fetal life: skin cells, hair, and other material floating around in the amniotic fluid.) After passing a handful of these sticky poops, a baby has something we refer to as “transition stools.” These poops are runny, green, and foamy. In fact, if your baby has a transitional stool when his diaper is off, you may see it shoot 12 inches through the air! But rest assured, they’re not dangerous and will fade into memory in a couple of days.
When a person’s stomach fills with food, it triggers a reflex that stimulates peristalsis. (Peristalsis is the name for the rhythmic contraction of muscles that push food from the beginning of the gastrointestinal tract to the end.) This explains why adults and older kids often have a bowel movement after eating. However, this reflex is much more active in babies, which is why they often poop while nursing. But the poop that comes out when your baby eats is waste from the feeding that went in hours ago.

It’s hard to see your baby cry, especially when she’s pooping. Parents often assume that babies are constipated if they strain or cry when they poop. Although this is true in older children, babies commonly grunt and strain with defecation because of a reflex that causes them to push when fecal material enters the rectum. However, if this behavior concerns you, be sure to mention it to the doctor at the baby’s next checkup. In rare cases, a baby’s anal opening may be too tight or her anus may be in the wrong position. Although rare, these anatomic variations can make it more difficult to pass stool.

Umbilical hernias are caused by a weakness in the ring of muscles that surround the belly button. Because of this weakness, abdominal fluid or intestinal contents can push on the skin covering the belly button causing a bulge. The bulge will be more noticeable if a baby is crying or if an older child is standing up.

Umbilical hernias are common and not serious. In the past, parents were told to bind the hernia so it would go away. This does not work and may create a rash on the baby’s abdomen. Fortunately, most resolve on their own by the time children start first grade. If they persist beyond this point, they may need to be repaired surgically.

Umbilical hernias rarely cause harm. Once in my 30-year career, a piece of intestinal fat got “stuck” in the hernia ring had to be fixed on an emergency basis. The way I knew something was wrong was because the area was red and the baby was crying. When I pressed on the hernia, instead of being easily pushed back in, it was hard and tender to touch.

One of the most common questions I get has to do with the color of a newborn’s bowel movements. The first stool that an infant has is a dark green, black substance called meconium. Babies pass meconium stools for a few days before they have something called transitional stools. Transitional stools are usually a medium green color and runny. In many cases, transitional stools can “shoot” out of a baby’s bottom like diarrhea.

Breastfed babies usually have loose, seedy or runny stools. They can be yellow, green or brownish in color. The reason parents worry about green stools in babies is because older children and adults only have green bowel movements when they are sick. There is a simple explanation for this.

The body uses bile acids to digest fats. Bile is pea green in color. In children and adults, waste moves through the large intestine slower than in newborns. This allows the “good” bacteria that live in the intestine to metabolize the bile, which converts it to a brownish color. Because fecal material moves through a newborn’s intestinal tract rapidly, there is less time for intestinal bacteria to convert the bile from green to brown. When children and adults have diarrhea, peristalsis is sped up causing green poops.