Why Are The Sleeping Cycles Of Babies So ‘Messed Up’?

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Babies have small stomachs and therefore wake up for night feedings 2 to 3 times in the evening. Genes also play a role in deciding their sleeping pattern.

Sleepless nights are like a rite of passage for newbie parents. However, sleep deprivation is not a good look on anyone, especially first-time parents suddenly juggling the weight of the world. So, what is it that prevents a newborn—and thus their parents—from sleeping through the night?

Newborn baby crying on the bed, selective focus(06photo)s
Parents tending to a cranky baby (Photo Credit : 06photo/Shutterstock)

Most parents are initially clueless when their baby brings the whole house down in the middle of the night with their wailing. Sometimes they’re hungry, other times they’re too hot or cold. There are times when it seems like they just want to play or cry for the heck of it. But like most things in life, there is a reason for the haywire sleeping pattern of a newborn.


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Do Babies Sleep In The Womb?

Mothers are used to sleepless nights even before their baby is born. During gestation, babies are exposed to the cycle of day and night, rest and wake, through the mother alone. However, a study conducted on 274 pregnant women showed that fetuses have a diurnal pattern of their own. Most women reported moderate to strong fetal movements in the evening. The constant movement of the mother in the daytime is thought to lull the baby to sleep, whereas the relative peacefulness of the night prompts the baby to kick around and make its presence known!

Image of a yawning newborn baby like 3D ultrasound of baby in mother's womb(Valentina Razumova)s
Yawning baby captured on a 3D Ultrasound (Photo Credit : Valentina Razumova/Shutterstock)

Scientists have debated that this could also be attributed to the failure to register the baby’s movements when the mother is busy during the daytime. Ultrasound tests of fetal activity, however, have shown heightened fetal activity at night and an increased probability of fetal dormancy in the morning. That being said, such activity is welcome during pregnancy, as it reduces the chances of a stillbirth.

Also Read: What A Baby Learns While Still In The Womb?

What Is The Sleeping Pattern Of A Newborn?

Babies sleep during most of the day and night in the initial few weeks following their birth. However, a plea for food and attention is heard regularly every 2 to 3 hours, often making parents worry whether their baby is getting enough sleep. 

Smiling baby girl lying on a bed sleeping on blue sheets(javi_indy)S
A baby peacefully sleeping (Photo Credit : javi_indy/Shutterstock)

At birth, newborns have yet to develop a Circadian rhythm. The Circadian rhythm is our internal biological clock that controls when we get sleepy by secreting a cocktail of hormones into our system. The hormones cortisol and melatonin, along with the body temperature cycle, dictate when we should sleep and when we should be wide awake. Of these, melanin production is of the utmost importance, as its levels determine the sleep/wake cycle. A spike in melatonin levels induces sleep and is therefore known as the sleep hormone.

Since infants do not have a set circadian rhythm, they sleep in short bursts throughout the day and night, rather than go on a sleep marathon every night like adults.

During the initial years of life, sleep evolves rapidly and is a profoundly complicated process. At first, the baby sleeps for a total of 16 to 17 hours, distributed almost equally over day and night.  By 8 weeks of age, cortisol rhythm develops; the production of the sleep hormone melatonin in the evenings has been recorded as early as  9 weeks. Body temperature cycle and circadian genes develop at 11 weeks, paving the way for the establishment of a more traditional sleep-wake cycle by 10 to 12 weeks of age. This means that the baby now easily sleeps through the night, that is, for at least 5 hours without waking up.

The total sleep duration of babies changes and decreases down to 14 or 15 hours by 16 weeks of age, and by 6 months it is only 13 to 14 hours. Although the need for daytime naps drops, the length of a “full” night sleep rises over the first year, causing a transition to more nocturnal sleep patterns, and giving new parents a welcome chance to rest.

Babies have no fixed routine and are oblivious to the concept of day and night, which affect the behavior and mindset of older children and adults. Infants also have small stomachs, so they wake up multiple times for food. They typically wake or move approximately every 40 minutes and wake up about 2 to 3 times at night for feeds before these nocturnal patterns are established.

Also Read: Why Do We Wake Up At Roughly The Same Time Every Morning?

Do Genes Play A Role In Deciding The Sleep Pattern?

Like most of our activities, our genes play a pivotal role in deciding our sleeping pattern! Parents who have trouble getting their youngsters to sleep through the night can be (somewhat) reassured by a study revealing that a major determinant of a baby’s night-time routine is merely the luck of the genetic draw. 

Canadian scientists analyzed the sleep patterns of 995 fraternal and identical twins in Quebec. They discovered that genes primarily decide if children stay asleep through the night or not. The ability of children to rest during the daytime, however, was found to be influenced more notably by environmental factors.

The Canadian researchers, however, were not checking for particular genes correlated with sleep in the study. Instead, they were examining whether there was a higher probability of identical twins to share sleep habits than fraternal twins, which was found to be true. This further suggested the role that genes play in deciding the sleeping pattern of an infant.

Another study investigated the AA-NAT gene, which controls the oscillating levels of melatonin in the body. The study identified that a single change from the nucleotide (letters that make up our DNA) guanine (G) to cytosine (C) at the –263rd position was a crucial determinant of a short sleep cycle. This mutation was found in 4 out of 5 short sleepers, but in only 1 of 5 long sleepers.

Environmental factors include the presence of the mother, light, temperature, room-sharing, transitional objects, media usage, noise, etc. Studies show that bedtime rituals like bedtime stories or lullabies before sleeping can make children sleep longer, and sleeping with parents and using a toy or a blanket (transitional objects) might decrease anxiety and promote healthier sleep. The use of a night-light or media usage, however, is found to suppress melatonin production.

Does The Unique Sleeping Pattern Of A Baby Play A Significant Role In Its Development?

Babies have a relatively shorter sleep cycle and spend considerably more time in REM (rapid eye movement sleep). In fact, REM sleep was first identified in infants! REM sleep, as the full name suggests, is a light sleep when your eyes move back and forth rapidly. It is also the stage in which you dream! Older children and adults sleep for fewer hours as a whole, but sleep for most of the night, unlike newborns. As you get older, you spend fewer hours in REM sleep, meaning that we dream more often as babies than as adults!

A study has indicated the presence of salivary melatonin during the initial few weeks of life, and showcased its rapid increase in the first 6 months to levels greater than those recorded in adults!

Wonky sleep is normal for all newborns and is actually important, given that it has been linked with physical growth as well as cognition.

The sleep of a baby might indicate the child’s cognitive and motor functions. Cognition studies indicate that disparities in sleep quality and quantity between individuals are especially significant for the development of language,  executive functions and memory. Studies that measured the connection between the physical growth of a child and its sleep found that children with poorer sleep had a higher chance of obesity.

However, these observations should be considered with caution. The studies have only established a connection between sleep and the body, but not how the sleep affects these changes exactly. Furthermore, results from studies performed on animals, like mice, aren’t always applicable to humans.

A study showed that prolonged REM sleep deficiency may affect cognitive development in mice, but such occurrences have rarely been recorded in humans. In humans, it is uncertain if: (1) the quantity and quality of sleep determines cognitive capabilities; (2) cognition and sleep mirror the maturation status as a whole; or (3) there is some other connection.

Further studies should account for environmental (e.g., household sleeping provisions, socioeconomic background) and parental factors (e.g., postpartum depression, degree of knowledge) that may influence these sleep-development studies.

you get no sleep meme

Be it genes or the environment, babies are sure to keep their parents awake through the night at least till they reach the age of 1. After that, both the child and the parents are blessed with a good night’s sleep—most of the time. Later in life, these ‘messed up’ sleep patterns resurface for children once they enroll in a university or become parents themselves!

Also Read: Why Is Sleep Important?

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References (click to expand)
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About the Author

Saloni Hombalkar has earned her Bachelor’s degree in Biomedical Sciences from SDSOS, NMIMS-Mumbai. She is an enthusiastic science communicator and hopes to share her passion for biology with as many people as possible. Apart from Biology, she enjoys discussing Marvel, learning to code, reading YA fiction and dramatic karaoke sessions.

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