Parents find dead newborn in teenager's bed.

Police are investigating after the parents of a 17-year-old girl discovered the body of a newborn baby boy dead in the bed of their daughter.

The teenager from San Diego in California appears to have given birth to the baby  in the day  before he was found by her parents.

The San Diego Union Tribune reports that the teenager’s parents called emergency services on Monday evening around 8pm from their home after they found the infant’s body while making their daughter’s bed.

The girl’s parents reported a “non-breathing” baby to emergency dispatchers, police said.

“The child appeared to be have been born hours or days prior,” police said in a statement.

“The parents of that minor found that child deceased in the bed anywhere from 24 to 36 hours later and called us,” Chula Vista Police Lt. Fritz Reber told NBC. 

The baby was full term. Via IStock.

Police said the newborn baby boy appeared to be full-term and weighed 7 pounds, 8 ounces (3.4kg).

It is reported that the teenage girl told police she had been unaware she was pregnant until she gave birth while she was in bed.

An autopsy has been conducted but a cause and manner of death has not yet been released.

The teenager’s unknown pregnancy is just the latest in a  string of women who have said they gave birth after not realising they were pregnant.

It is reported that the teenage girl told police she had been unaware she was pregnant until she gave birth while she was in bed. Via IStock.

Writing for The Conversation Helen Cheyne, a Royal College of Midwives professor at the University of Stirling in Scotland said that “cryptic pregnancy” or “pregnancy denial,” is “not particularly rare.”

“In fact, they are estimated to occur in around one in 2,500 cases, suggesting around 320 cases in the UK annually, or a potential headline story almost every day.”

Cheyne said some women never experience the telltale symptoms of pregnancy — morning sickness and noticeable weight gain.

“The physiology and psychology of concealed and cryptic pregnancy are different and both are complex,” she wrote.

“However, they may be difficult to distinguish in these rare and tragic cases. There are many uncertainties surrounding childbirth and even today many, superficially straightforward aspects of pregnancy and birth remain poorly understood.

While we may continue to read these news reports with some disbelief, we must ensure that we respect and protect the women behind these tales of the unexpected.”

Authorities in San Diego are investigating to determine whether a crime occurred in the newborn’s baby’s death.