A flat head in an infant shows up as a noticeably flattened area on the back or side of the skull, replacing the smooth, egg-shaped curve you’d expect when looking at a baby’s head from above. Nearly 47% of infants have some degree of head flattening at 3 months of age, so it’s one of the most common things parents notice during those early weeks. What it looks like depends on where the flattening is and how pronounced it’s become.
How to Spot It From Above
The easiest way to check your baby’s head shape is to look straight down from above while your baby is sitting upright or lying face-up. A typical infant head looks like an evenly rounded egg. Both ears should sit at the same height and the same distance from the front and back of the head. The forehead and cheekbones should look symmetrical, without one side appearing fuller or more pushed out than the other.
When a flat spot is present, you’ll see a break in that smooth oval shape. One area will look pressed in or squared off instead of gently curving. Depending on the type, the head may look lopsided from above (like a parallelogram) or unusually wide from front to back.
Flat on One Side: Plagiocephaly
The most recognizable type of flat head is plagiocephaly, where one side of the back of the skull is flatter than the other. From above, the head looks asymmetrical, almost like a parallelogram tilted to one side. The flattened side pushes other features slightly out of alignment. You may notice that one ear appears pushed forward compared to the other, or that the forehead, eye area, or cheek on the opposite side looks fuller or more prominent.
These facial changes happen because the skull is soft and interconnected. When pressure flattens one area at the back, the bones shift slightly, causing the forehead on the opposite side to bulge forward and one ear to drift out of position. In mild cases, you might only notice the flat spot itself. In moderate to severe cases, the ear misalignment and facial asymmetry become more obvious.
Flat Across the Back: Brachycephaly
Brachycephaly looks different. Instead of one side being flat, the entire back of the head is flattened evenly. From the side, the back of the skull appears unusually straight or vertical rather than gently rounded. From above, the head looks wider than expected, and the front of the head may bulge outward slightly. The overall shape is short from front to back and broad from side to side.
Because the flattening is symmetrical, you won’t see the ear misalignment or lopsided forehead that comes with plagiocephaly. The main visual cue is that the back of the head lacks the normal rounded curve, and the head appears disproportionately wide.
Other Clues Parents Notice
A bald patch or area of thinned hair on the back of the head often shows up right over the flat spot. This happens because friction from lying in the same position wears down the hair in that area. It’s not harmful on its own, but it’s a reliable indicator of where the most pressure has been.
Some babies with a flat spot also hold their head tilted to one side or strongly prefer looking in one direction. This can be a sign of torticollis, a condition where a neck muscle on one side is tight and shortened. About 75% of the time, it’s the right side that’s affected. You might notice your baby’s head tilting toward one shoulder while the chin points the opposite way, and the baby resists turning their head the other direction. That limited range of motion keeps the same part of the skull pressed against the mattress, creating or worsening a flat spot. In young babies with torticollis, a small, painless lump may be felt in the tight neck muscle during the first few weeks, though it typically disappears by 6 months.
Mild vs. Moderate vs. Severe
Doctors measure the severity of a flat head by comparing the diagonal distances across the skull. When the difference between the two diagonals is less than 5 millimeters, the head shape is considered normal. A difference of 5 to 10 millimeters is classified as mild. Moderate cases fall between 10 and 15 millimeters, and anything above 15 millimeters is severe.
In practical terms, a mild flat spot may only be visible when you’re specifically looking for it from above, and hair often conceals it entirely. Moderate flattening is noticeable to others and typically comes with visible ear misalignment or facial asymmetry. Severe cases are apparent even at a glance, with obvious differences between the two sides of the face.
Why It Happens
A baby’s skull is made of soft, flexible plates with spaces between them. This design allows the head to pass through the birth canal and gives the brain room to grow rapidly in the first year. But that same softness means the skull molds to whatever surface it rests against. When a baby consistently sleeps or lies with the same part of the head on a flat surface, that area gradually flattens.
The rise in flat head cases over the past few decades is directly linked to the safe sleep recommendation that babies sleep on their backs. Decades ago, the prevalence was estimated at roughly 1 in 300. Now, some degree of flattening appears in nearly half of all 3-month-olds. The good news is that rate drops sharply as babies gain head control and start spending more time upright. By age 2, only about 3.3% of children still show noticeable flattening.
What Helps It Improve
Most mild to moderate cases improve on their own as babies become more mobile and spend less time on their backs. The most effective thing you can do is supervised tummy time while your baby is awake. Starting with two or three short sessions of 3 to 5 minutes each day, you can build up to 15 to 30 minutes of total daily tummy time by around 2 months. As your baby gets older and stronger, sessions can be longer and more frequent. Tummy time takes pressure off the back of the skull, strengthens neck and shoulder muscles, and gives babies the strength to reposition their own heads.
Alternating which direction your baby faces in the crib, switching the arm you hold them with during feeding, and giving them reasons to turn toward the less-preferred side all help distribute pressure more evenly across the skull.
For moderate to severe cases that don’t respond to repositioning, a cranial remolding helmet may be recommended. These helmets work by leaving space where the skull needs to grow while gently guiding it away from the flattened areas. They’re most effective when started before 12 months of age, while the skull plates are still soft and actively growing. The earlier the helmet is fitted within that window, the shorter the treatment time tends to be.
If torticollis is contributing to the flat spot, stretching exercises or physical therapy to loosen the tight neck muscle are typically part of the treatment plan. Addressing the neck tightness is essential, since the flat spot will keep returning if the baby continues favoring one position.