Down syndrome is a condition where the fetus has an extra 21st chromosome. Therefore, there are 47 chromosomes instead of the normal 46. The chromosomes contain the genetic material that determines our inherited characteristics. Down syndrome results in mental retardation and, sometimes, physical problems such as heart defects. The risk for Down syndrome is higher in older women, but it also occurs in young women. The AFP+ test is used to indicate whether a woman has an increased risk for Down syndrome. If the AFP+ test indicates that the chance is as high as that of a woman over 35 years of age, further testing may be recommended.