Scientists estimate that 12 million babies have been born as a consequence of vitro fertilization (IVF) and other reproductive technologies. All over the world, IVF is an especially popular treatment for adults struggling to conceive naturally.

But stark new research has now warned of a dangerous potential consequence of the treatment. The study, led by Sweden's University of Gothenberg, claimed that babies born this way are 36% more likely to experience a major heart defect.

This threat is particularly increased in circumstances of of twin and triplet births which reportedly occur in 11% of IVF pregnancies compared with 1-2% of natural conceived pregnancies, according to Twins Trust.

Professor Ulla-Britt Wennerholm, who led the project, told ScienceDaily: "We already know that babies born after assisted reproductive technology have a higher risk of birth defects in general however, we have found a higher risk also in congenital heart defects, the most common major birth defect.

"The fact that the risk of heart defects is similar regardless of the type of assisted reproduction used may indicate that there is some common factor underlying infertility in parents and congenital heart disease in their babies."

Mayo Clinic explains that congenital heart defects occur due to a problem with 'the structure of the heart that a child is born with'. While some infants don't need treatment, others may experience more complicated or even life-threatening issues.

As part of the study, scientists analysed data from more than 7.7 million children born across Denmark, Finland, Norway and Sweden across a few different timeframes. Data was then compared among those conceived through different means including IVF, embryo freezing and naturally.

Among those born to assisted reproductive technology, the scientists now suggest there may be 'increases in cases of congenital heart defects worldwide'. Dr Nathalie Auger from University of Montreal Hospital Research Centre in Canada and colleagues, who also worked on the project, added: " Patients who use assisted reproductive technology tend to differ from the general population. These patients may have underlying morbidities that affect both fertility and the risk of heart defects."

For the latest health news, advice and symptoms to watch out for sign up to the Daily Express’ free health newsletter