A hiatal hernia develops when part of your stomach pushes up through the opening in your diaphragm where your esophagus passes through. This opening, called the hiatus, is normally about 2 cm long and fits snugly around the esophagus. When the muscles and connective tissue around it weaken or stretch, the top of the stomach can slide upward into the chest cavity. Most hiatal hernias result from a combination of age-related tissue changes and repeated pressure on the abdomen, though some people are born with an unusually large hiatal opening.
What Happens Inside Your Body
Your diaphragm is a dome-shaped muscle that separates your chest from your abdomen. The esophagus passes through a small gap in this muscle before connecting to the stomach just below it. A band of elastic connective tissue called the phrenoesophageal ligament anchors the junction between your esophagus and stomach in place, keeping it firmly below the diaphragm.
A hiatal hernia forms when this anchoring system fails. The ligament loses its elasticity, the muscle fibers around the opening weaken, and the gap gradually widens. Once that happens, the top portion of your stomach can slip upward through the enlarged opening. In some cases, the tissue becomes so stretched that the stomach doesn’t slide back down to its normal position after you swallow, staying partially lodged in the chest.
The Main Causes
Repeated Abdominal Pressure
Anything that repeatedly pushes pressure upward against your diaphragm can stretch and weaken the hiatal opening over time. The most common sources of this pressure include chronic coughing or sneezing, chronic constipation and straining on the toilet, frequent vomiting, intense exercise or heavy lifting, and pregnancy and childbirth. Think of it like wearing out the elastic waistband on a pair of pants: no single moment of stretching causes the damage, but years of repeated force eventually loosen the tissue beyond its ability to snap back.
Aging
Age is one of the strongest predictors of hiatal hernia. The connective tissue holding everything in place naturally loses elasticity as you get older, and the muscles of the diaphragm lose tone. Data from the Multi-Ethnic Study of Atherosclerosis illustrates this clearly: hiatal hernia prevalence was just 2.4% among people in their 50s, rising to 7% in the 60s, 14% in the 70s, and nearly 17% in the 80s. The steady climb reflects decades of cumulative wear on tissue that simply doesn’t regenerate well.
Obesity
Carrying excess abdominal weight creates constant upward pressure on the diaphragm. A BMI over 30 is an established risk factor, and the relationship appears to be ongoing: research has shown that people whose hiatal hernia grew larger over time had a significantly higher average BMI (around 30) compared to those whose hernia shrank or resolved on its own (average BMI around 27). Losing weight won’t necessarily reverse an existing hernia, but it can slow progression and reduce symptoms.
Being Born With a Larger Opening
Some people are simply born with a wider-than-normal hiatal opening. When the diaphragm doesn’t fully form during fetal development, abdominal organs can shift upward into the chest cavity. Severe cases, known as congenital diaphragmatic hernias, are detected in infancy because they interfere with lung development. Milder cases may go unnoticed for years, only becoming apparent when age or weight gain tips the balance and the stomach begins to herniate through an opening that was always a little too large.
The Two Types
Not all hiatal hernias look the same. The two main types differ in which part of the stomach moves and where it ends up.
A sliding hiatal hernia is by far the more common variety. The junction where the esophagus meets the stomach slides upward through the hiatus, pulling the top of the stomach with it. These hernias often move up and down depending on your position and activity. Bending over, coughing, or lifting something heavy can push the stomach further into the chest, while standing upright may allow it to slip back down.
A paraesophageal hernia is less common but potentially more serious. In this type, the esophageal junction stays in its normal position, but a portion of the stomach squeezes up through the hiatus alongside the esophagus. Because the stomach folds up next to the esophagus rather than sliding along it, there’s a risk that the herniated portion can become trapped or have its blood supply pinched off.
How Pregnancy Contributes
Pregnancy creates a perfect storm of hiatal hernia risk factors. The growing uterus steadily increases pressure inside the abdomen, pushing upward against the diaphragm for months. Hormonal changes during pregnancy also soften connective tissue throughout the body, which can loosen the ligament that normally holds the stomach in place. On top of that, the nausea and vomiting common in early pregnancy add further episodes of abdominal pressure. Many pregnancy-related hiatal hernias resolve after delivery as abdominal pressure drops and tissues recover, but in some women the damage to the hiatal opening persists.
What It Feels Like
Small hiatal hernias often cause no symptoms at all. Many people have one and never know it, only discovering it incidentally during imaging for something else. When symptoms do appear, they usually relate to acid reflux: the displaced stomach allows stomach acid to flow more easily into the esophagus, causing heartburn, regurgitation, and a sour taste in the mouth.
Larger hernias can produce a feeling of fullness or pressure in the chest after eating, difficulty swallowing, or shortness of breath if the herniated stomach presses against the lungs. You’re more likely to notice symptoms during activities that compress the hernia, like bending forward, lying flat after a meal, or straining. A hernia over 2 cm is generally considered large enough to be clinically significant, though symptoms don’t always correlate neatly with size.
Who Is Most at Risk
The biggest risk factors are age, obesity, and anything that chronically raises abdominal pressure. Research identifies age, gender, ethnicity, and BMI as the top predictors. Women develop hiatal hernias more often than men, partly due to the added risk from pregnancy. People with chronic respiratory conditions that cause persistent coughing, those with long-standing constipation, and anyone who regularly performs heavy lifting are also at elevated risk.
There’s no single event that “gives” you a hiatal hernia in most cases. It’s the accumulation of years of pressure, tissue aging, and sometimes an anatomical predisposition that eventually allows the stomach to push through. Understanding these causes matters because some of them, particularly obesity, constipation, and heavy straining, are modifiable. Managing those factors won’t guarantee prevention, but it reduces the mechanical forces that drive the condition forward.