Edwards Syndrome is also known as Trisomy 18. Edwards Syndrome is a condition which is caused by an error in cell division, known as meiotic disjunction. When this happens, instead of the normal pair, an extra chromosome 18 results (a triple) in the developing baby and disrupts the normal pattern of development in significant ways that can be life-threatening, even before birth. A Trisomy 18 error occurs in about 1 out of every 2500 pregnancies and 1 in 6000 live births. The numbers of total births are much higher because it includes significant numbers of still births that occur in the 2nd and 3rd trimesters of pregnancy. Unlike Down syndrome, which also is caused by an extra chromosome, the developmental issues caused by Trisomy 18 are associated with more medical complications that are more potentially life-threatening in the early months and years of life. Babies who are carried to term will be born alive, and baby girls will have higher rates of live birth than baby boys.