Anterior Fontanel (Soft Spot)

My son has the biggest anterior fontanel I have ever felt (I have felt thousands!!!!!). My pedi says he is not too concerned. I am not either, but my doctor does make me nervous by telling me he wants me to report ANY developmental lag to him right away. On one hand he is blasé, then he turns around and sounds alarmed. I am really confused. It measures 3 inches front to back, 2 5/8 inches across. My baby is 6 months old and his head is growing fine (75th percentile across the chart), he is starting to sit, rolls all over, reaches etc. Am I driving myself crazy worrying for nothing???
P.S. I chatted with you in chat the other day!
Alex Sweeney RNC – Pediatric Care Coordinator – Ormond Memorial Hospital – Ormond Beach, Florida

Anterior Fontanel (Soft Spot)

Dr. Greene’s Answer:

How crazy-making! The message you are left with is, “Don’t worry, but your son might be developmentally delayed — and it’s your responsibility to pick up on the clues.” No wonder you feel the way you do. Before I answer your question, Alex, I want to tell readers who don’t have your training a little about the anterior fontanel.

The anterior fontanel, or soft spot on a baby’s skull, is a cause of concern for many parents. Elsewhere, the baby’s brain is protected by a wall of bone; here only soft, squishy tissue separates the brain from the traumas of the outside world. The soft spot seems so vulnerable. I spoke with a mother today who had never touched her son’s soft spot — she was afraid she would put her finger through it.

In truth, the soft spot is another example of the amazing design of the human body. At birth there are six soft spots, but only two are noticeable (the largest, up on top, is the anterior fontanel). The loose connections of the skull bones that intersect in the soft spots make labor and delivery possible. Without this flexible anatomy, either human babies would have to have smaller brains or human mothers would have to have wider hips if any babies were to be born.

The value of the soft spot isn’t gone when you first hold your baby in your arms. Far from making the baby more vulnerable, the soft spot protects a baby from injury. True, it makes some uncommon accidents more dangerous (landing head first on top of a car’s radio antenna), but for the common falls experienced by all babies, the soft spot cushions and protects — making the skull function rather like a football helmet.

Every week, frantic parents rush into my office after their babies have fallen off a bed or table or highchair. It happens so quickly, babies can fall even with careful and attentive parents — it’s even happened to me, but don’t tell :^). When babies fall, they usually land head first, since their centers of gravity are in their heads (adults’ centers of gravity are in our bottoms). The head hits the floor with a terrible, ripe-melon-like “thwunk.” Thanks to the cushioning of the soft spot, most of these head injuries are quite minor. And by the way, although the spot is soft, it actually consists of a surprisingly tough fibrous membrane.

At birth, babies’ soft spots come in a very wide range of sizes. If the soft spot is small, it will usually enlarge over the first several months. Conversely, large ones tend to get smaller. By the time a baby is 2 months old, the anterior fontanel is usually about 1 and 1/4 inch across (actually one by one and a half inches), +/- 3/4 inch (Journal of Pediatrics, 80:749, 1972). A persistent, larger anterior fontanel is usually completely fine, but is sometimes associated with a variety of uncommon disorders (list adapted from Nelson Textbook of Pediatrics, Saunders, 2007):

  • Achondroplasia, or true dwarfism. You would already know, by size and appearance, if your son were a dwarf.
  • Apert syndrome. These babies have webbed digits, broad thumbs and big toes, and characteristic faces. Again, you would already know.
  • Cleidocranial dysostosis. These babies have tiny to absent collarbones, tiny chests, and abnormally shaped skulls. Again, evident before 6 months of age.
  • Congenital hypothyroidism. This condition might not be picked up, if it weren’t for the newborn screening blood test. Before newborn screening, large fontanels were a common way to diagnose hypothyroidism. If your son’s screening test was normal, no worry here.
  • Congenital rubella. This virus is mild in children, but devastating to unborn babies. Those who survive generally are blind, deaf, and with significant heart murmurs. These are not healthy appearing babies.
  • Hallerman-Streiff syndrome. Characterized by big foreheads, tiny eyes (with cataracts), and very tiny, underdeveloped noses, these babies are usually blind from birth and remain blind despite surgery. The diagnosis is usually made shortly after a baby is born.
  • Kenny-Caffey syndrome. An extremely rare inherited skeletal disorder associated with low blood calcium levels and short stature.
  • Hydrocephalus, or water-on-the-brain. In hydrocephalic babies, the fontanel is kept open by the pressure and by the rapidly increasing head size. I’m glad your son’s head is growing fine.
  • Hypophosphatasia. This inborn error of metabolism often is severe and lethal in newborns. There is a very mild form of the disease which can be diagnosed by x-ray (moth-eaten appearance of the bones) or blood or urine tests. These kids look like kids with rickets, and are not developmentally delayed.
  • Intrauterine growth retardation. Kids who don’t grow well in the uterus (for any reason) will often have persistent large fontanels. Once again, you would already know.
  • Osteogenesis imperfecta. This condition is characterized by fragile bones, hyperextensible joints, deep blue sclerae (the white part of the eyes), and unusual, translucent teeth. The diagnosis is sometimes missed in the mild forms of this disease, but it can be identified on x-ray. These babies all have multiple bone fractures, which lead to the x-rays.
  • Prematurity. The soft spots in premature babies are larger than average, but there is no known problem from this.
  • Pyknodysostosis. These children are short, with unusual jaws, underdeveloped or absent collarbones, and very wrinkled fingers. The diagnosis may be clinched by x-ray. Pyknodysostosis is most common in children whose parents are close relatives of each other. It has been suggested that the artist Toulouse-Lautrec had pyknodysostosis, but I don’t know anything about his parents.
  • Russell-Silver syndrome. These kids have congenital short stature, asymmetric limbs, and small incurved fifth fingers. This is usually identified at birth, or shortly thereafter.
  • Trisomy 13, 18, or 21. These unfortunate chromosomal problems are readily detectable at birth. I went to the grave of my niece today. It still hurts.
  • Vitamin D deficient rickets. This is rare in the United States, but could happen in exclusively breast-fed babies whose mothers do not take vitamins or go outside in the sunlight, at least briefly, each week. It is more common in dark-skinned individuals. Early on, rickets can be diagnosed by x-ray. Soon it is evident in curved limbs, potbellies, and a horizontal groove between the chest and the abdomen. In many kids, if you press on the skull, you feel a ping-pong-ball-like sensation.

Alex, when your pediatrician said everything was probably fine, he was right. He is also right to be vaguely concerned that large anterior fontanels are sometimes associated with certain syndromes, some of which (like the trisomies) involve developmental delay. Now you know what these syndromes are. The serious ones have already been ruled out. Even the mild ones are very unlikely in your thriving son. I would relax and enjoy your son, who is just starting to sit. Soon he’ll be moving across the floor. For most kids, the anterior fontanelle closes not long after they get steady on their feet (at 9 to 18 months). It stays open just long enough to protect them as they stumble their way toward walking on their own. How quickly it all goes!

Dr. Alan Greene

Dr. Greene is the founder of DrGreene.com (cited by the AMA as “the pioneer physician Web site”), a practicing pediatrician, father of four, & author of Raising Baby Green & Feeding Baby Green. He appears frequently in the media including such venues as the The New York Times, the TODAY Show, Good Morning America, & the Dr. Oz Show.

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  1. catherine

    Dr.Green,

    My daughter is 10 days old. When she was born she had a really bad cone shaped head. It had do to how long I was pushing. My concern is sense I gave birth my daughter has had this big soft lump on the left size of her head. It’s 2 inches front to back and 1 1/2 inches side to side. The nurse at the hospital said its from her hitting the bone as I was pushing her out and she said it would go away. It has not gone away nor has it gotten any smaller. My question is should I worry about this?

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  2. pat

    I do not feel the pulse on my daughter’s fontanelle. She is six months now and am worried.

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  3. James Wu

    Dear Dr. Greene, my son is 19 months old and his fontanel is still not closed yet. His height is also behind the average level. His mother and I are quite concerned and worry that the fontanel closure may affect his growth.
    In this case, doctors back in my country China generally will give some shots of Vitamin D3 to interfere. But here in US we went to a doctor and he told us we need no worry about that at all. Dear Dr., what shall we do now? Your help is highly appreciated.

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  4. Carla

    My 2 month old has a very small soft spot. It’s as small as the round tip of my index finger. I can’t say if it was like this since he was born because I don’t remember checking it. I notice it being relatively small when he had just turn 2 months.

    I have other kids and theirs I remember it being much bigger. I was able to feel and see it pulse, with him I don’t.

    I became concern when I had to have him seen when he developed a cough (he contracted a virus that caused bronchiolitis and he was hospitalized). His normal pediatrician wasn’t able to see him so another did. She couldn’t find his soft spot and became concerned and asked his pediatrician to take a quit look. She didn’t seem too concerned, in fact he was seen by her many times after birth and never seem concern about it, until now.

    When he was hospitalized none of the doctors seem concerned about it. After he was released from hospital I was asked to have him checked by his pediatrician asap to make sure he was doing fine. That’s when she asked me to bring him in in a month (when he turns 3m).

    Now I’m very scared. The anxiety is cutting my breastmilk supply and I have read many articles online, most seem scary. Now my question is, should I be this concerned? Could it be possible the size of his soft spot is normal? He has developed well, doesn’t seem to be delayed on his milestones, he makes eye contact with me, smiles at me and tries to use his vocal cord!

    Please help me. Give me hope all will be fine!

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  5. yaz

    Hello Dr Greene
    My baby is 2 months and I’ve been told his soft spot has closed. He has been referred to perform surgery on him can you give me some info please

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  6. Elizabeth

    I disagree with the congenital hypothyroidism comment — only because it took 30 years for my endocrine disorder to be correctly diagnosed. I was born with the large anterior fontanelle, which extended all the way down my face, to just above my hard palette (looked like my nose was splitting in half).

    This turned out to be due to in utero exposure to pesticides (endocrine interferons) — dioxin, in particular. The fontanelle has no cranial tissue above my hairline, is over 1/4″ deep and is nearly bald.

    I not only have been hypothyroid my entire life (rather serious, pensive and low energy), but I also have other HPTA Axis issues — which are all suspected to be caused by the dioxin exposure. The “normal” thyroid reference range is being disputed because it suggests that everyone in the sample had optimum levels — however, at the time the reference range was established, there was a measurable portion of our population that had already been exposed to endocrine interferon pesticides in food, water, soil, etc.

    I would suggest there’s nothing to worry about… UNLESS she lives anywhere near or down stream from any Dow chemical plant. If she has, I would suggest a sonogram of the thyroid to confirm if it is normal size (mine is the size of a lima bean). When I was finally put on thyroid medication (despite my TSH T4 being “normal”), I finally discovered what it felt to feel alive rather than half asleep.

    A simple sonogram would have literally changed the path of my life, and could potentially prevent lost years of someone else’s.

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  7. Rozanna

    my daughter is 42days old and still has the soft spot on top. I’m not the most gentle and careful parent in the world, so I would like to know, is small pressure on the soft spot dangerous? I worry cause I’ve bumped it a couple of times and am now a little reluctant to wear her since it’s always then that I accidentally bump her with my chin (she’s fussy most of the time after feedings, throws up easy, so holding her upright on my chest without it is tiring). what should I look out for if it happens to know if it is bad (apart from her crying from pain)? she usually only gets startled and just falls back asleep.

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  8. sweety

    Hello Dr Greene,
    My son is 6 months old n based on radiographs his size of anterior fontanelle is small & measures abt 5-6 mm so his doc’s says we have to do CT scan of the skull for better assessment of craniosynostosis n follow up as clinically warranted. So pls kindly give me ur opinion.

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  9. tyler

    my 2 month old has a soft spot like normal but then it feels like there is a like of softness running from his soft spot to his for head is this normal or is there something wrong its nore on the right side of his head?????

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  10. joanne

    My son had cranial surgery at a year old I noticed on top of his head a soft spot I’ve asked doctor said its normal second opinion please

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  11. nick

    Dr green, my son is 1 and 1/2 I brushed my hand over his head to move his hair and felt his soft spot had not gone. My other kids theirs went around 1 yrs of age. Is there any concern?

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  12. Mariska

    Thank you so much for such a good explanation. Also for listing all of the sicknesses. My little girls is 29 months and hers is not closed yet. The pediatrician sent her for thyroid tests, but it came back normal. She is a happy, healthy and very busy 2 year old. She is short and petite for her age, but other than that no sign of weird sicknesses. Just wondering what the procedure is now? Do we just wait until it closes, or should other tests be done?

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  13. clare

    My son is 4 and his soft spot hasnt closed or appeared to being to close it is 4cm by2cm this has got bigger if anything he is a healthy little boy so why would this be he has been referred but im worried sick

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  14. sir war

    Dr. Greene,
    thanks for your explanation on anterior fontalle. my son’s own worries me because his anterior frontalle extends to the forehead, slightly close to his nose, is it normal?

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