IVF babies are 45 per cent more likely to die before their first birthday, a study of almost three million children has found.
Researchers in Sweden compared the outcomes of babies conceived naturally and through assisted reproductive techniques.
Babies from a frozen embryo had a more than two-fold higher risk of death than babies conceived naturally in the first few weeks of life.
It may be because so-called 'test tube babies' are often born premature, the team said. This can make their immune system weaker.
They emphasised the risk of death was still very small for babies across all groups.
IVF babies are 45 per cent more likely to die before their first birthday, a study of almost three million children has found. Stock photo of an IVF embryo
One in seven couples struggle with infertility, and assisted reproductive techniques (ART) have helped millions of people have healthy babies in recent years.
More than 75,000 IVF treatment cycles were carried out across the UK in 2017, according to the fertility watchdog, the Human Fertilisation and Embryology Authority (HFAE).
Prior studies show, however, that IVF-pregnancies come with an increased risk of low birth weight, prematurity and birth defects. These risks have partly been linked to the increased probability of twin-births after IVF-treatment.
In the current study, the researchers at Karolinska Institutet in Sweden analysed data on 2.8million children born in Sweden over a period of 30 years. Some 43,500 of these were the result of assisted reproduction.
In total, 7,236 children died before one year of age, of whom only 114 were conceived with assisted reproductive techniques.
After adjusting for confounding factors such as the mother's age and earlier infertility, the researchers found that the children conceived through IVF had a 45 percent higher risk of death before their first birthday than children conceived naturally.
The level of risk varied depending on which type of assisted reproductive technique was used, and how many days had passed since birth.
During the first week of life, the children conceived after transfer of a frozen embryo had a more than two-fold higher risk of death.
This was, however, based on only a small sample of children conceived with frozen embryos.
After one week, the risk dropped to about the same level as the naturally conceived children.
Infants conceived from transfer of a fresh embryo or with the help of an intracytoplasmic sperm injection (ICSI) did not have a higher risk of death.
The risk gradually declined after the first weeks of life. Beyond one year of age, the risk of mortality was similar for all children regardless of conception method.
'Our results indicate that the kind of assisted reproductive technique used may make a difference, and therefore it is important to further