Forensic scientists in Norway have been perfoming research on the hearts and brains of an estimated 700 dead infants without parental consent, it has been revealed.

An investigation by the Norwegian newspaper VG revealed that, for three decades, researchers have been taking the essential organs of babies in connection with Sudden Infant Death Syndrome (SIDS) and other research.

Permission was not requested for the research, which was carried out on children between birth and three years old, as the country's Institute of Public Health (Folkehelseinstituttet) believed it would be too distressing for parents.

The practice began in the midst of a SIDS epidemic in the 1980s. Currently, Norwegian law only requires the consent of relatives for hospital autopsies, but there is no clear legislation regarding forestic autopsies.

"If you have heard the cries of the parents who lost their children, then you will understand," Professor Torleiv Ole Rognum, who was involved in the research, told VG.

"When we started the project we autopsied up to three toddlers a day, who had died of cot death. My driving force has always been to find the cause of SIDS."

It is unknown exactly what causes SIDS, but it is thought to be the result of a combination of factors.

Experts believe SIDS occurs at a particular stage in a baby's development and that babies who are vulnerable to certain environmental stresses may be affected.

The body parts were reportedly earmarked for studies until at least 2020, but Rognum added that current legislation regarding autopsies will likely soon be revised.

When questioned whether parents would now get the chance to opt out of the research, Rognum told newspaper the Local: "Yes, I have a great appreciation of for that. I do not want us to perform research on material where the parents don't want that themselves. But I have spoken with many parents who have lost their children, and none of them have been negative towards research.

"In 1984, it was much easier to take samples for research from forensic autopsies. These [the legislation] have been tightened, and that's fine. Now I hope that the research on material from right autopsies are regulated in line with hospital autopsies."

Rognum also claimed that he had advocated stricter regulations in the past.

According to VG, the children involved in the research had died as a result of disease, SIDS, accidents, mishandling of healthcare or murder. Police and prosecutors requested autopsies as their deaths were unexpected.

The body parts were removed, the cavities filled with silicone and the cadavers sewn up to look natural.

"We have launched a thorough investigation to clarify if some of the business is in violation of the law and what corrective measures eventually must be implemented," said Bjørn Magne Eggen, a director at the Institute of Public Health.

Five of Norway's largest hospitals performed the examinations for the Institute of Public Health.