'Down's syndrome' is the name of a birth defect that occurs in about one in every 800 babies. It's caused by the presence of three chromosome-21s in the nucleus of the child's cells, rather than the normal two. It can result in a child having a number of external and internal physical abnormalities, as well as being mentally retarded. Women who already have had one Down's syndrome child, who become pregnant after age 35, or who have difficulty conceiving are among those most at risk to give birth to a child with Down's syndrome. Whether or not a child has developed Down's can be detected prior to birth by a procedure known as an 'amniocentesis' (am-nee-oh-sen-TEE-sis), in which a small amount of fluid is withdrawn from the sac that surrounds the fetus and examined under a microscope. The procedure is done by inserting a long needle through the pregnant woman's abdomen. Although the procedure is generally considered safe, there are some risks involved to both the mother and the fetus. There's currently no cure for Down's syndrome, but there are specially-designed therapies to help children who are affected make the most of their developmental and physical capabilities and lead a full life. For more information about this condition, contact a healthcare professional.