PDF Summary:The Happiest Baby on the Block, by Harvey Karp

Your baby won’t stop crying. The screams start up at any time of day or night and continue for hours, no matter what you do. The doctor says you just have to wait it out; your friends and family give conflicting advice, none of which works. You’re pretty sure you’re going to lose your mind. Luckily, you don’t have to: In The Happiest Baby on the Block, pediatrician Harvey Karp offers a solution to your problem.

In our guide, we’ll outline Karp’s theory about why babies develop colic—crying for hours a day multiple times per week—and how caregivers can manage it. Through our commentary, we’ll offer extra advice and research from parenting experts and pediatricians on how to keep your baby happy and healthy—and get some sleep for yourself in the process.

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3) Shushing

The third method Karp discusses is shushing, or providing some kind of white noise or ambient sound. This noise, he explains, helps simulate the relatively loud environment of the womb—namely the sound of blood rushing through arteries. (Shortform note: While in the womb, a fetus hears more than just the internal sounds of blood pumping and digestion—they also learn to recognize the voices of their parents by the third trimester. This is potentially why the sound of your speaking voice can soothe them as well.)

How to Shush Your Baby

Karp recommends using some form of white noise for all sleeping and crying periods. These noises should be moderately loud—your baby needs to be able to hear the shushing over their own crying, though you can reduce the volume when they start to relax. White noise also doesn’t help babies sleep until a volume of about 60 decibels, the equivalent of a shower or dishwasher running. As long as you keep the noise around this level, it won’t hurt your baby’s hearing.

In the moment, you can shush your baby by making a “shh” sound a few inches from their ear. For more extended periods, Karp recommends using continuous sounds (rather than something irregular or sporadic like ocean waves). He suggests using higher-pitched white noise to soothe crying and lower-pitched white noise to facilitate sleeping. You can keep using white noise throughout the first year, as your baby will likely continue to struggle with sleep as their calming response fades.

(Shortform note: In addition to using white noise, you can also help keep the noise in your baby’s room consistent through soundproofing—especially if you live in a high-traffic area, or somewhere else with lots of loud, sudden outside noise. You can soundproof your baby’s room with heavy blackout curtains, by closing doors and windows tightly, or even with soundproofing fabric or foam for walls and ceilings. However, Karp emphasizes that a too-quiet room can also contribute to colic, which suggests that you should pair soundproofing with white noise.)

4) Swinging

Karp’s fourth method is swinging, or rhythmically moving your baby. While inside the womb, fetuses are jiggled, bumped, and rocked nearly constantly whenever their mothers move. Swinging helps simulate this motion to trigger a calming response.

(Shortform note: After the book’s publication, Karp designed and promoted a robotic bassinet that automatically swings your baby. He suggests it’s a natural extension of his other techniques, allowing caregivers to rest while their baby is still soothed. Some pediatricians believe more research needs to be done to understand the effectiveness of mechanical versus caregiver swinging, though.)

How to Swing Your Baby

Karp recommends soothing your baby through small, fast movements focused on the head rather than large swings of their entire body—moving only a few inches side to side two to three times per second. Increase the amount of motion if your baby is fussy, and decrease it once they start to calm down. As you swing your baby, support their head and neck and keep them in line with their body to prevent injury and discomfort. In addition to cradling and moving your baby around, you can also generate the same kind of jiggling motion through rhythmic patting, car rides, or walks in a stroller or baby carrier.

Karp asserts that gentle swinging and jiggling won’t hurt your baby or make them nauseous—the motions necessary for shaken baby syndrome or intense dizziness are much larger and more forceful.

(Shortform note: You might feel worried that swaying your baby too quickly or jiggling motions will injure them. The National Center on Shaken Baby Syndrome elaborates on the difference between the type of movement Karp suggests and more violent shaking that can cause a baby harm. They explain that swaying or more vigorous motion like taking your baby on a jog, bike ride, or car trip won’t be enough to cause shaken baby syndrome, or SBS—even a sudden car stop or fall off of furniture isn’t forceful enough. SBS, they explain, requires several seconds of violent motion or impacts to the head and neck.)

5) Sucking

Finally, the fifth method Karp recommends is sucking—providing your baby with a pacifier to suck on. Babies tend to suck their own fingers frequently while in the womb, and so sucking activates the calming response. It’s also pleasant because your baby associates sucking with sating their hunger. Karp explains a pacifier is preferable to finger sucking, though, because it requires less coordination and is easier to wean your baby off of (since you can easily take it away).

(Shortform note: If your baby is in the habit of sucking on their thumb or fingers, don’t worry—most grow out of it by six months or two to four years of age. Pediatricians suggest that so long as they don’t continue sucking their fingers beyond the age of four, it’s not an issue and won’t impact your baby’s oral development.)

How to Use a Pacifier

Karp recommends using a silicone pacifier because silicone is sturdier than rubber. He explains that babies tend to have favorite shapes for pacifiers, so you’ll have to experiment to find their favorite. Pacifiers are best used after the other techniques to keep your baby calm, since it can be hard to get your baby to suck while upset.

(Shortform note: Other parenting experts agree with Karp that pacifiers are usually best used once your baby is already starting to calm down. They explain that a calm baby is more open to new things, while an upset baby is more likely to be annoyed by having an unfamiliar object put in their mouth. Your baby will also likely be more receptive to a pacifier after a feeding; if they’re hungry, they might be frustrated by sucking on a pacifier and not getting food.)

To teach your baby to keep the pacifier in their mouth, periodically pull it away. Your baby will respond by sucking harder to get it back and through this process learns how to keep it in their mouth. Karp recommends using a pacifier until your baby is around five to six months old, then weaning them off of it. This prevents them from forming an emotional attachment to the pacifier, which makes it harder to wean. (Shortform note: Don’t worry—pulling a pacifier away slightly doesn’t make your baby suck harder out of frustration. Instead, it triggers their automatic reflex to maintain their suck, keeping their pacifier in. This reflex naturally wears off at four to six months of age, so weaning after this point will be a process of managing your baby’s habits and emotional states rather than fighting against their natural reflexes.)

Part 2: Underlying Medical Conditions

While Karp argues a majority of colic cases are due to over- or understimulation—and therefore can be addressed through the five methods in the previous section—he acknowledges there are some instances where underlying medical issues are responsible for colic.

In Part 2, we’ll cover medical and health-related causes of colic and Karp’s recommendations for addressing them.

How Underlying Medical Conditions Cause Colic

Karp explains that while many people and even some doctors assume all colic has a medical cause, only 5-10% of colic cases have an underlying medical cause. In these cases, your baby’s cries are signs of discomfort due to physical symptoms. Karp notes the most common physical ailments that cause colic: allergies and constipation. Let’s explore how to manage each in more detail.

Allergies

Allergies are responsible for 90% of medically-caused colic. Babies can be exposed to common allergens—such as cow’s milk, eggs, peanuts, tree nuts, wheat, soy, and fish—through breast milk depending on the breastfeeding parent’s diet.

Karp explains that babies with allergies tend to cry throughout the day and night. They may also have diarrhea, indicated by mucus in their stools. If you suspect your breastfed baby has an allergy, start keeping track of how long and how often they cry. Then, have the breastfeeding parent cut the foods listed above out of their diet for a week. If your baby’s crying stays the same, they likely don’t have an allergy. If your baby starts crying less, reintroduce small amounts of these foods to the parent’s diet one at a time to see if one makes your baby cry more—if one does, it’s likely their allergen.

(Shortform note: If you’re hoping to avoid your child developing allergies altogether, breastfeeding may be the best preventive measure—research suggests breastfed babies tend to suffer fewer food allergies than their formula-fed counterparts. While scientists aren’t exactly sure why, some believe it has to do with certain molecules and microorganisms unique to breastmilk that provide genetic instructions to help protect babies from developing food allergies.)

Constipation

Karp explains that some cases of colic can be due to pain or discomfort from constipation. If your baby is bottle-fed, you can try improving their bowel movements by changing their formula mix or adding a tablespoon of water or prune juice to their formula once per day. Otherwise, you can try helping your baby coordinate their rectum by bicycling their legs, massaging their bottom, or inserting a greased thermometer about a half inch to an inch into their anus.

Signs of Constipation

Recognizing when your baby is constipated can be difficult, as babies naturally have fewer bowel movements than adults. But there are several signs pediatricians point to as indicators of constipation:

• Your baby passes harder, drier, or more pellet-like stools.

• Your baby seems to struggle with passing stools, arching their back or crying while doing so.

• Your baby’s general rhythm of bowel movements changes.

If you notice your baby showing any of the above symptoms, consider trying some of the above methods and seeing if they help.

When to See the Doctor

In addition to the more common medical causes of colic, Karp also notes several signs that indicate you should take your baby to the doctor. Note that while these signs may indicate more serious issues, said issues are responsible for less than one percent of medically-caused colic. Karp recommends seeing a doctor if:

• Your baby pees fewer than five times per day and/or has dark yellow urine.
• Your baby gains fewer than four to seven ounces of weight per week (about a pound every two weeks).
• Your baby cries all day long without any periods of calm, or has a particularly shrill, high-pitched, sharp cry.
• Your baby is lethargic—they sleep twice as long as usual or have a weak suck.
• Your baby cries during or right after feeding.
• Your baby’s temperature goes below 97.5° or above 100.4°.
• Your baby vomits more than an ounce at a time, more than five times a day, or has yellow or green vomit.

(Shortform note: While some of the symptoms listed above are easy to objectively recognize as serious—a high fever, frequent vomiting, or lack of weight gain, for example—others (like whether your baby is lethargic) are a bit more based on subjective observation. Ideally, you should have an easy-to-contact, reliable pediatrician to ask about both “objective” and “subjective” symptoms. Parenting experts note that a good pediatrician should not only recognize problems and provide treatment, but should also be available to answer your questions and provide reassurance. And whether or not your baby requires medical treatment for their symptoms, you’ll likely feel better for having asked.)

Part 3: Poor Sleep

Finally, Karp notes that irregular or insufficient sleep can contribute to colic. In Part 3, we’ll explain why this is the case and go through Karp’s advice for improving a baby’s sleep.

How Poor Sleep Causes Colic

Karp explains that newborns tend to sleep between 14 and 18 hours a day, usually for two to four hours with an hour of time awake in between. While asleep, babies tend to cycle between lighter and deeper forms of sleep every hour—if something wakes them up during a deeper sleep cycle, they tend to have an easier time getting back to sleep. During a lighter cycle, though, a baby who has trouble self-soothing may start crying because they’re unable to get back to sleep.

(Shortform note: Pediatricians explain that part of the reason why babies sleep so erratically is because they can’t tell the difference between day and night. The circadian rhythm, or “internal clock” that determines how our bodies respond to light and darkness, doesn’t develop until around three to six months of age. This is why babies so often don’t cooperate with the sleep schedules of their caregivers—they don’t know any better. And much like adults, babies are worse at emotional regulation while tired, meaning poor and disjointed sleep contributes to colic.)

Helping Your Baby Sleep Better

While the soothing techniques mentioned in Part 1—swaddling, holding on the side/stomach, shushing, swinging, and sucking—are often enough to help your baby sleep, Karp offers several additional tips for helping your baby get better, longer stretches of sleep:

1. Feed your baby at the right time: You can help your baby sleep for longer stretches by ensuring they aren’t hungry at night. If your baby still seems hungry after their last meal before sleeping, feel free to feed them a bit more. You can also wake them up between 10 PM and midnight for a feeding to help them sleep through more of the night.
2. Plan your baby’s naps: To help your baby sleep better, make sure to wake them up after they’ve napped for two hours—this ensures they’re awake for their next feeding cycle and will eat enough throughout the day. However, don’t let them stay awake too long during the day either. Otherwise, they’ll get used to only falling asleep when overtired. This will prevent them from learning how to sleep when they’re less exhausted.
3. Help your baby learn to self-soothe: After you put your sleeping baby in their crib, wake them up for a few seconds by jostling them or scratching the bottom of their feet. This will help them learn how to get back to sleep by making them practice it regularly.

Create a Sleep Routine

“Bedtime” techniques like the ones Karp offers are best used as part of a consistent routine, pediatricians explain. This is because consistently doing the same things before sleeping will help your baby associate the two, signaling to them when it's time to sleep. Here’s how you can incorporate Karp’s techniques into a sleep routine for your baby:

• Incorporate a “hunger check” or late feeding into your baby’s nighttime sleep routine, so they learn to associate nighttime feeding with sleep.

• Have your baby nap at around the same times every day for about the same length, so they associate these specific times of day with being asleep.

• Put your baby into their crib while they’re drowsy, but not asleep. Then, once they fall asleep, you can scratch the bottoms of their feet like Karp recommends. This way, your baby can practice self-soothing as well as actually having to fall asleep while in their crib.