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Did You Know Babies Cry At Night To Delay Birth Of Siblings? And Other Reasons

Babies tend to wake at night, and that's something all new parents are used to. The reasons for this vary from sleep cycle to underlying health conditions. However, did you know that sometimes babies wake up at night to delay the birth of siblings? Shocking right!

A recent study looked more into this aspect and found that babies, in fact, wake at night to delay the possible addition of a new family member.

Read more on Babies Cry At Night To Delay Birth Of Siblings.

Is Your Baby Crying At Night?

If yes is your answer, it's time you know they are subtly (yet loudly) hinting they don't want a brother/sister. In a new study published in the journal Evolution, Medicine and Public Health, Harvard evolutionary biologist David Haig suggested that babies cry at night to delay the birth of another sibling [1].

Haig began the study in 2014, and more conclusive evidence was published recently.

Here are the observations that caused the researchers to reach their conclusion:

1. Link to evolution: Certainly, delaying the birth of a sibling would not be intentional on the part of the babies but simply a result of the fact that throughout our species' evolutionary history, babies with more time before their next sibling was born survived more often - all points to the Darwinian tactic, that a competitive environment or situation in which only the fittest persons or organizations prosper. This may be due to the increased amount of time, attention, and resources given to babies who have spaced further apart [2][3].

2. Ovulation period of the mother: You may be wondering now why crying at night would delay the birth of a sibling. The reason isn't that frustrated parents would be interrupted from having sex. Since mothers do not ovulate while nursing, the longer they nurse, the longer it will take them to have another child. Nursing at night and on-demand, rather than according to a schedule, seems to delay ovulation return - which in turn delays the possibility of conceiving [4].

3. Breastfed vs bottle-fed: It was also pointed out that babies fed from bottles wake up less often during the night than breastfed infants [5].

4. Mom and dad's genes: A baby with a genetic predisposition to waking at night is evolutionarily expensive for the mother - even though it increases their chances of surviving, it reduces the number of babies she can have overall. For a father, this is less of a problem - he can always reproduce with another woman. Accordingly, genes inherited from fathers should promote waking more than genes inherited from mothers [6][7].

"Natural selection will have preserved suckling and sleeping behaviours of infants that suppress ovarian function in mothers because infants have benefited from the delay of the next birth," the researchers said. They also added that "maternal fatigue can be an integral part of an infant's strategy to extend the inter-birth interval. More frequent and intense nursing, especially at night, is associated with prolonged infertility [8]."

Other Reasons Why Babies Wake At Night

When your baby wakes up in the middle of the night gurgling, cooing, and playing with her toes, it is one thing - but when she appears to be in distress, it is another. Cries are not always signs of discomfort; your baby may be dealing with temporary sleep disruptors like illness, teething, separation anxiety, or other age-appropriate fears [9][10].

Here are some of the other reasons why babies can wakeup at night:

  • Teething
  • Behavioural and developmental changes
  • Shifting from pacifiers or bottles
  • Infections (infants typically have an increased chance of infections after six months of age)

On A Final Note...

Babies don't know how to fall asleep when tired or wake up when well-rested - it is something they need to learn. All sleep disruptions and frequent night waking are completely normal and will change as she grows. However, if you feel something is wrong with your baby, go to the doctor as soon as possible.

Story first published: Saturday, July 9, 2022, 16:12 [IST]
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