Curing Colic: The 4th Trimester

by Harvey Karp, M.D.

"Just put cotton in your ears and gin in your stomach!"
--19th Century colic advice

Infant crying has been attributed to everything from the evil eye to exercise for the lungs to brain immaturity to severe stomach pain. In fact, the very word "colic" comes from the ancient Greek word "kolikos" meaning crampy pain and shares its root with the word "colon". Yet, despite all these theories, this extremely common problem has remained one of the longest standing medical mysteries on record.

And, it's tough to be around these red-faced, screaming young babies. It makes your skin sweat, your blood pressure climb, and causes great frustration when nothing you do seems to calm them. No wonder, most of us who have ever had to care for a crying newborn have probably muttered to ourselves, "Why couldn't they just come with a crying off-switch?" Well, perhaps they do and we just overlooked it!

In 1980, as a fellow in Child Development at UCLA, I learned something that astounded me -- some cultures around the world are "colic-free". In other words, their babies usually calm in a minute or less. And, I began to wonder, "Had those parents discovered the 'off-switch'?"

This question lead me on a twenty-year study of infant crying and a search for ancient techniques to help the 20% of our young babies who fuss and scream for more than 3 hours a day." Now, I think I know what's going on with these babies and it's not gas.

Gas is mostly a lot of hot air

Gas seems a logical cause of a baby's crying. After all, fussy infants often double up, make a pained sounding cry, have rumbling stomach, and pass gas. It's no wonder generations of physicians have given newborns opium, antispasmodics and burp drops to settle them.

However, although it's clear that some babies cry from milk allergy (~10-15% of colic) and a few from acid reflux (~3% of colic), intestinal pain can't be the cause of most cases of colic because:

  1. Colic starts at 2 weeks, ends at 3 months and peaks in the evening, yet gas starts at birth and lasts long after the 3-month birthday and occurs all day long.
  2. Fussy babies often calm in cars and with rocking…yet these don't stop pain.
  3. X-rays of infants show more gas after they stop crying then before they begin.
  4. Colic is totally absent from some cultures around the world…but gas isn't.
  5. Antispasmodic drugs may work because they are also highly sedating.
  6. Two double-blind studies have shown that simethicone is no more effective for crying than water.

As odd as it sounds, I think the real reason our babies get colic is because, in a certain respect, they're born 3 months too soon!

The Missing "4th Trimester"

Baby horses can walk and even run on their very first day of life. They are truly ready to be born when they leave their mother's womb. By comparison, our newborns are more like fetuses than infants. They have irregular breathing, tremors…and even need help to burp. It is only after 2-3 months that they smile, coo and finally seem ready to be here.

Our babies don't have big strong bodies, like horses, but they do have big brains. In fact, they are so big, at 9 months giving birth is an almost impossible squeeze. A dilated cervix is 10 centimeters in diameter (31.4 cm circumference) while a newborn's head has a circumference of 34-35 cm. Our big-brained babies have to come out after 9 months gestation; however, in many ways, they could really use a few more months of the stimulation of the uterus.

Yes, I did say stimulation. In the womb, fetuses are constantly massaged by the muscular walls of the uterus, frequently jiggled and 24/7 they are surrounded by the crash of blood whooshing through the placental arteries (a noise that is louder than a vacuum cleaner!).

Most parents around the world intuitively mimic the rocking, holding and shushing of the uterus, but in our culture, we are mistakenly taught to whisper and tiptoe around our babies, believing that they need a quiet and still environment. Nothing could be further from the truth! Rather than being over-stimulated, most of our babies are seriously under-stimulated.

Recreating the sensory milieu of the womb is so important for newborns, not because they are nostalgic for the "good life" they had inside, but because it actually triggers an important, but previously unappreciated neonatal reflex, I call the calming reflex.

The Calming Reflex

The calming reflex is a "primitive" reflex (or, group of reflexes) that is almost an automatic off-switch for a baby's crying. I believe it evolved over the millennia not as a way to calm fussy babies, but as a way to calm fussy fetuses. During the last months of pregnancy, this inborn response virtually entrances fetuses, thus lessening the chance they'll move around too much and accidentally kink the cord or get stuck in a position that would make delivery impossible.

The 5 S's

Unlike the knee reflex, which has only one way of being triggered, there are 5 things a parent can do to activate their baby's calming reflex -- the 5 S's:

  1. Swaddling -- tightly, with the arms down
  2. Side/stomach position -- while the back is safest for sleeping it is least effective for calming crying
  3. Shushing -- loud, continuous white noise
  4. Swinging -- rhythmic movement
  5. Sucking -- the icing on the cake

(Dr. Karp's approach is discussed in his new book and video, The Happiest Baby on the Block. For more information, see his website.)


  • Konner MJ, Ethological Studies of Child Behavior, Cambridge Press, 1972
  • Brazelton TB, Crying in infancy, Pediatrics 4:579-588, 1962
  • Forsythe BW, Colic and the effect of changing formulas, J Pediatrics 115:521-526, 1989
  • Poole S, The infant with acute, unexplained, excessive crying, Pediatrics 88:450-455, 1991
  • Lester B, Barr R, eds, Colic and Excessive Crying, Report of the 105th Ross Conference on Pediatric Research, 1997
  • Illingsworth R, The 3-months colic, Arch Dis Child 29:165, 1954
  • Danielsson B, Hwang CP, Treatment of infantile colic with surface active substance (simethicone), ACTA Ped Scan 74:446-450, 1985
  • Metcalf T et al, Simethicone in the treatment of infantile colic, Pediatrics, 94:29-34, 1994

Harvey Karp, M.D., author of The Happiest Baby on the Block, is an assistant professor of pediatrics at UCLA School of Medicine, with a private practice in Santa Monica, California. He was trained by some of America's top pediatricians, including Dr. T. Berry Brazelton, and in 1981, Dr. Karp received the prestigious Ehrmann Fellowship to study crying and colic. Dr. Karp is a nationally renowned expert on children's health and the environment, and an authority on breastfeeding, appearing on ABC News' "World News Tonight," CNN, Lifetime Channel and numerous national radio programs.

Copyrighted &copy Harvey Karp. Permission to republish granted to, LLC.