Babies get hernias when a natural opening in the abdominal wall fails to close during development, leaving a gap where tissue or intestine can push through. This isn’t caused by anything a parent did or didn’t do. It’s a structural issue that happens before or shortly after birth, and it affects between 1% and 4% of full-term babies. In premature infants, the rate jumps to as high as 30%.
The Two Most Common Types in Babies
Nearly all hernias in infants fall into two categories: inguinal hernias (in the groin area) and umbilical hernias (at the belly button). Each one has a different cause, a different look, and a different outlook, but both come down to the same basic problem: a hole that should have closed on its own didn’t fully seal.
How Inguinal Hernias Form
During pregnancy, a small tunnel of tissue called the processus vaginalis extends from the abdomen into the groin. In boys, this tunnel allows the testicles to descend from the abdomen into the scrotum. Once the testicles are in place, the tunnel is supposed to close. When it doesn’t, a loop of intestine can slip down through that open passage, creating a visible bulge in the groin or scrotum.
Girls have a similar structure. The round ligament, which supports the uterus, travels through the inguinal canal into the outer tissue of the labia. If the tissue lining that canal stays open, intestine or an ovary can push through, causing a bulge near the groin or labia.
This explains why inguinal hernias are far more common in boys. Males make up roughly 88% of all infant inguinal hernia cases, with a male-to-female ratio of about 5 to 1. The anatomy involved in testicular descent simply creates more opportunity for the tunnel to remain open. Interestingly, the left side tends to close earlier during fetal development, which is why right-sided hernias are more common.
Premature babies face a much higher risk because the processus vaginalis normally closes during the final weeks of pregnancy. Babies born early miss that window. Among premature boys, inguinal hernia rates range from 7% to 30%. Premature girls also face elevated risk, with rates around 2%, and both prematurity and female sex are associated with higher odds of hernias appearing on both sides.
How Umbilical Hernias Form
Umbilical hernias happen at the belly button, where the umbilical cord connected during pregnancy. After birth, that opening in the abdominal wall muscle is supposed to close as the cord stump heals. In some babies, the closure is incomplete, leaving a gap where a small amount of intestine or abdominal fluid can bulge outward beneath the skin.
These hernias are common and usually harmless. You’ll typically see a soft bulge at or near the belly button that becomes more noticeable when your baby cries, strains, or coughs. It often flattens when the baby is calm or sleeping. Unlike inguinal hernias, most umbilical hernias resolve without any treatment. By age 3, about 82% have closed on their own. By age 5, that number reaches nearly 89%.
What a Hernia Looks and Feels Like
The hallmark sign is a bulge that comes and goes. You may only notice it when your baby is crying, coughing, or straining during a bowel movement. The bulge often gets larger with effort and smaller (or disappears entirely) when your baby relaxes or falls asleep. It’s usually soft to the touch and not painful in the early stages.
For inguinal hernias, the bulge appears in the groin, the scrotum in boys, or near the labia in girls. For umbilical hernias, it shows up right at the belly button. In either case, if you can gently push the bulge back in and it returns later, that’s a classic presentation of a reducible hernia.
When a Hernia Becomes Dangerous
Most hernias in babies are not emergencies, but they can become one quickly if the tissue gets trapped. This is called incarceration, and it happens when the intestine (or other tissue) pushes through the opening and can’t slide back. If blood flow to the trapped tissue gets cut off, it becomes a strangulated hernia, which requires emergency surgery.
Girls are actually more likely than boys to experience incarceration of an inguinal hernia: about 17% of girls compared to 12% of boys. Warning signs include a bulge that suddenly becomes hard, swollen, or won’t go back in when your baby is relaxed. Other red flags are severe or worsening pain (your baby may cry inconsolably), nausea and vomiting, and skin color changes around the bulge. The skin may turn reddish or darker than usual. If the skin becomes pale and then darkens, that suggests the blood supply is compromised.
How Hernias Are Treated
The treatment path depends entirely on the type. Inguinal hernias don’t close on their own and always require surgical repair. Current clinical guidelines recommend prompt surgery after diagnosis to prevent the risk of incarceration or strangulation. The procedure is straightforward: surgeons close the open passage, and recovery is fast. Most children return to normal activity within 48 hours, and recurrence is rare, happening in fewer than 1 in 100 children regardless of whether the repair is done with a traditional open incision or a laparoscopic approach.
Umbilical hernias, on the other hand, usually get a “wait and see” approach because the vast majority close on their own during the first few years of life. Even among children whose umbilical hernia is still present at age 3, about 35% will close by age 5. Surgery is typically only considered if the hernia persists beyond age 4 or 5, or if it causes symptoms.
Risk Factors That Increase the Odds
The single biggest risk factor is prematurity. The earlier a baby is born, the less time the abdominal wall and inguinal canal have had to complete their natural closure. Each additional week of gestation decreases the odds of a bilateral hernia by about 5%. Being male is the other major factor for inguinal hernias, driven by the anatomy of testicular descent. Family history also plays a role, as the tendency for the processus vaginalis to remain open can run in families. About 5% of all males will develop an inguinal hernia at some point in their lifetime, with many of those cases originating in infancy or early childhood.