The long-term effects of in vitro fertilization (IVF) on the mother and on the child have always been a topic of speculation. Louise Joy Brown, the first person born who was conceived via IVF (used to be called the “first test tube baby”) turned 32 last July and she herself is a mother to a 3-year old who was conceived naturally. Researchers could only monitor and record what they observe and know about Louise and thousands, maybe millions of IVF babies like her as they grow, reproduce and eventually die. Only time can tell whether there are long-term health effects associated with this type of assisted reproduction.
One of the first results on the ongoing observation of IVF children are out – coming from Sweden.
Swedish researchers at the University of Lund followed-up 26,692 children born after conception via IVF between 1982 and 2005. Cancer data were extracted from Swedish Cancer Register and comparison was made between cancer patients who were born after IVF and those were not. The results indicate an increased risk for cancer among those conceived by IVF.
The expected number of cancer cases in the general population is 38. Among the IVF children of the same age, 53 were diagnosed with cancer, equivalent to a 1.42 total cancer risk estimate. The most common forms of cancer diagnosed among IVF children were:
- 18 of them with hematologic cancer (15 of them acute lymphoblastic leukemia)
- 17 with eye or central nervous system tumors
- 12 with other solid cancers
In addition, 6 cases of Langerhans histiocytosis were reported where 1 case is expected.
The researchers ruled out maternal age, number of previous babies delivered, smoking, subfertility, previous miscarriages, body weight and multiple births as the cause of the increased cancer risk. Although, it can be speculated that the mode of conception might play a role, the researchers think this may not be the case.
Instead, factors that should be considered are genetic traits from the parents, many of whom may have had health problems that manifested in the infertility that made use IVF in the first place.
Another factor is the fact that IVF resulted in many multiple births that in return led to preterm delivery. Premature babies have higher risks for health problems than babies born at full term.
In addition, the study only looked at Swedish children, and the Swedish population has relatively lower biodiversity compared to say, the UK or the US where IVF is commonly used as assisted reproduction technique. Thus, findings in these children might not be true in IVF children elsewhere.
The authors are quick to reassure parents of IVF children that although they found “a moderately increased risk for cancer in children who were conceived by IVF”, absolute risks are still very low – less than 1%.