For the first time, Scot researchers claim to have disclosed the medical vagueness that has left scientists scratching their heads for nearly 50 years: why thalidomide, a drug used to treat as an ideal for morning sickness in pregnant women, caused severe birth defects in the late Fifties and early Sixties. Dr. Neil Vargesson, of Aberdeen University, accords the motive to a constituent of the drug that prohibited the growth of new blood vessels, and subsequently caused limb defects in the developing embryo. “We have put to rest a 50-year puzzle, in finally deducing how thalidomide triggers limb defects and why it appears to target limbs preferentially.

This is an important discovery. Many models have been suggested as to how these defects were caused but now we know how it worked,” the Scotsman quoted the lecturer in Developmental Biology as saying. “This is the first paper to conclusively show that it is the anti-angiogenic property of the drug - that element that inhibits new blood vessel formation - that is to blame for the defects. The drug prevented early blood vessels going into the limb,” Vargesson added.  Importantly, Thalidomide was put up for sale in a number of countries around the world from 1957 until 1961, as soon as it was withdrawn from the market after being found to be the origin of what has been called "the biggest medical tragedy of modern times”. It is not recognized precisely how many global victims of the drug there have been, even though estimates range from 10,000 to 20,000.  Although it was not permitted in the United States for the reason that Dr. Frances Kelsey from the Food and Drug Administration (FDA) affirmed there was inadequate proof of the drug’s wellbeing in humans. After that thalidomide was almost immediately banned worldwide when it was exposed that it caused disastrous birth defects. According to the March of Dimes (MOD, November 1998), "More than 10,000 children around the world were born with major malformations, many missing arms and legs, because their mothers had taken the drug during early pregnancy. Mothers who had taken the drug when arms and legs were beginning to form had babies with a widely varying but recognizable pattern of limb deformities. The most well-known pattern, absence of most of the arm with the hands extending flipper-like from the shoulders, is called phocomelia. Another frequent arm malformation called radial aplasia was absence of the thumb and the adjoining bone in the lower arm. Similar limb malformations occurred in the lower extremities. The affected babies almost always had both sides affected and often had both the arms and the legs malformed.

In addition to the limbs, the drug caused malformations of the eyes and ears, heart, genitals, kidneys, digestive tract (including the lips and mouth), and nervous system. Thalidomide was recognized as a powerful human teratogen (a drug or other agent that causes abnormal development in the embryo or fetus). Taking even a single dose of thalidomide during early pregnancy may cause major birth defects."