Activation of the maternal Igf2 gene during egg formation or very early in development causes Beckwith-Wiedemann Syndrome (BWS). While children with BWS have a variety of symptoms, the most common and obvious feature is overgrowth. Babies with BWS are born larger than 95% of their peers. They also have an increased risk of cancer, especially during childhood. BWS occurs once in about 15,000 births. However, in babies that were conceived in the laboratory with the help of artificial reproductive technology (ART), the rate of BWS may be as high as 1 in 4,000. This and other evidence of imprinting errors is prompting some to call for further investigation into the safety of common ART laboratory procedures. (Source)