When Louise Brown was born at Oldham General Hospital in 1978, her arrival brought even more excitement than your average infant. Her birth prompted a flurry of media attention, commentary from the man who would soon become Pope John Paul I, and a Nobel Prize for physiologist Sir Robert Edwards. Why all the fuss? Louise was the first child born as a result of in-vitro fertilization – the original “test-tube baby.”
The historical consequences of Louise Brown’s birth may be a matter of record, but the medical consequences of assisted conception remain somewhat uncertain. While most children born after assisted conception are healthy, there is an increased risk of low birth weight, prematurity, congenital malformations, and epigenetic defects (such as those that lead to Beckwith-Wiedemann syndrome, a pediatric overgrowth disorder associated with tumor development). In theory, epigenetic changes might increase the risk of childhood cancer, an association observed in prior studies.
With this in mind, Dr. Carrie L. Williams (University College London, England) and colleagues performed a large population-based study that sought to estimate the overall and type-specific risk of cancer among children born after assisted conception. To do so, the records of all children born after assisted conception in Great Britain between 1992 and 2008 were linked to a population-based registry of childhood tumors. The cancer risk among these children was then compared to that in the general population.
Of the 106,013 children born by assisted conception, 108 were identified as having developed cancer during an average follow up of 6.6 years. Compared to the general population, children born after assisted conception had no increase in cancer risk overall (108 cases observed vs. 110 expected; P=0.87) and no increase in risk for leukemia, neuroblastoma, retinoblastoma, central nervous system, and renal and germ cell tumors. However, there were significantly more hepatic tumors and sarcomas than expected (6 cases observed vs. 1.8 expected [P=0.03] and 20 cases observed vs. 8.6 expected [P=0.002], respectively). How are we to interpret these findings?
“These findings are generally reassuring,” says internist and NEJM Deputy Editor Dr. Mary Beth Hamel. “The increased risk of hepatic tumors and sarcomas raises important questions for the research community, but the absolute risks observed were small.” The authors point out in their discussion that there are a number of potential explanations for the observed increase in these tumors, including confounding by low birth weight or chance findings due to multiple hypothesis testing.
With a recent announcement estimating that five million children have been born using assisted reproductive technologies since 1978 (and about half of those since 2007), interest in the consequences of assisted conception is sure to remain strong for years to come.