“It is important to note that even if we on a group level can see a somewhat increased risk of infant mortality after in vitro fertilization (IVF), the absolute risk for each individual is still very small,” says Anastasia Nyman Iliadou, associate professor at the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet and senior lead author. “It is also reassuring to know that there is no increased risk of mortality in this group of children beyond the first year of life.”

More and more women seek help to become pregnant and the achieving of pregnancies made possible with assisted reproductive techniques have increased in recent years. In most cases, these pregnancies have a happy outcome with a healthy baby. 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.

Analyzed data on 2.8 million singletons

In the current study, the researchers selected only singleton children and compared mortality in children conceived through different types of assisted reproductive techniques with children who were conceived naturally. They analyzed data on 2.8 million 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 1 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 1 year of age 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. The risk gradually declined after the first weeks of life.

Type of assisted reproductive technique may be important

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 than the children conceived naturally. 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)—where a single sperm is injected into the egg—did not have a higher risk of death than naturally conceived children, irrespective of how many days had passed since birth.