The Fourth Trimester. A new addition to the Merriam-Webster Dictionary!

LOS ANGELES, Nov. 15, 2021 /PRNewswire/ — About 20 years ago, pediatrician Dr. Harvey Karp wrote a parent guide, The Happiest Baby on the Block. In it, he shared his belief that one of the most important things for new parents to understand was a pretty unknown idea called the fourth trimester. Today, that obscure name has so thoroughly penetrated the minds of parents and doctors that the celebrated Merriam-Webster dictionary has included it in their newest edition. Inclusion in the dictionary acknowledges that fourth trimester is a part of a worldwide cultural awakening to the importance of this stage of life…not only for babies but for new parents, too.

What is the fourth trimester?
The fourth trimester is the first three to four months of a baby’s life after birth. The word "trimester" implies that the baby is still a fetus…and that’s on purpose! A newborn’s brain and nervous system are not fully developed at birth, making them more fetus-like than baby-like.

Where did the term "fourth trimester" come from?
Dr. Karp first heard the term in the late 1970s when he was working on the child abuse team at UCLA. At that time, he saw so many babies come in who were severely injured—even killed—for the simple offense of crying. He became deeply curious about what medical doctors had not been able to figure out—the cause of colic (severe persistent crying seen among babies 1-4 months of age).

He found that, thanks to evolutionary changes, human babies are born about three months before they’re technically "ready." In fact, they had to be born three months early because a baby’s developing brain and skull have gotten so big by the end of the third trimester that they can barely safely fit through the birth canal.

When did the "fourth trimester" become well-known?
In 2002 Karp used The Happiest Baby on the Block to share what he had learned from his research and in his practice as a pediatrician. He discovered that parents could best create that womb-like fourth trimester experience for their babies with what he called "The 5 S’s," which consists of swaddling, shushing, swaying, sucking, and holding babies in a side/stomach position (for soothing, not for sleep). In the book, he explained how the 5 S’s help trigger a baby’s calming reflex—a never-before recognized neurological response that develops deep in a baby’s brain months before they are born—basically nature’s "off switch" for fussing.

Since then, millions and millions of parents across the globe have turned to the 5 S’s to calm crying! So, while he did not coin the term "fourth trimester," Karp’s book helped to bring the notion of the fourth trimester into the consciousness of parents and physicians alike.

What do parents need to know about their baby’s fourth trimester?
It’s important to create a womb-like environment during a newborn’s fourth trimester. For instance, swaddling mimics the warm hug inside the womb, white noise stands in for the constant loud whooshing of blood pulsing through the uterine arteries, and swinging replicates the jiggling sensation of being inside Mom’s belly for every step she took. These are three of the 5 S’s…and they’re also the cornerstone of SNOO, the #1 safe baby bassinet created by Karp.  SNOO was specially designed to provide the fourth-trimester care that babies need by automatically responding to fussing with womb-like rocking, white noise, and the snug embrace of a safe swaddle.

Acknowledging this special period in a family’s life is a good first step. Karp is hopeful that it will help push more innovative solutions that will allow new parents and their babies to thrive in the fourth trimester…and beyond!

Dr. Harvey Karp is a world-renowned pediatrician and child development expert. His celebrated Happiest Baby/Happiest Toddler books and videos have guided millions of parents and are translated into 30 languages. In 2016, Dr. Karp debuted SNOO Smart Sleeper, a new class of responsive infant bed designed to add 1-2 hours to a baby’s sleep, quickly soothe crying and to improve safety by preventing dangerous rolling. SNOO won the National Sleep Foundation Innovation of the Year award as well as 20 other top national and international honors. Medical studies are underway to evaluate SNOO’s potential to reduce postpartum depression, infant sleep death and to improve the care of infants withdrawing from opiates.

Maury Rogoff

SOURCE Happiest Baby, Inc.