Babies wake up at night to delay birth of sibling

Washington, April 10: Here is an interesting finding by the

University which suggests that babies aren't as innocent as they seem - Infants who wake up during the night to be fed are really trying to delay the birth of a younger brother or sister !

The study says that shorter delays between the birth of siblings is linked to higher mortality rates. This means that a Darwinian tactic has developed in breast feeding children, in an attempt to reduce competition to improve their survival, the paper claims.

The instinct likely developed over thousands of years, the paper suggests.

During the first six months after birth, breast feeding acts as a natural contraceptive.

The study explains what could be the reason for babies waking up often in the night at around six months after their birth. It is around the time when mothers are becoming fertile again, said professor David Haigh, who led the study.

The research paper was published on Thursday in the journal Evolution, Medicine and Public Health. David said: "Natural selection will have preserved suckling and sleeping behaviours of infants that suppress ovarian function in mothers, because infants have benefited from delay of the next birth."

"Maternal fatigue can be seen as an integral part of an infant's strategy to extend the inter-birth interval."

He added: "More frequent and more intense nursing, especially at night, is associated with prolonged infertility."

Evidence from babies with Angelman syndrome suggests it may be fathers' genes that are responsible, he said.