Babies with monosomy X are females who have one X chromosome instead of two. Unfortunately, a high proportion of pregnancies with monosomy X will result in a miscarriage in the first or second trimester of pregnancy. Babies with monosomy X that make it to term may have heart defects,learning difficulties, and infertility. In most cases, girls with monosomy X will need extra medical care including hormone therapies at various stages of life.

Boys with Klinefelter syndrome have an extra X chromosome (XXY). This condition can be associated with learning difficulties and behavioral problems. Men with Klinefelter syndrome may be infertile. About 1 in 1,000 babies will be born with Klinefelter syndrome.

Girls with Triple X syndrome have an extra X chromosome (XXX). Girls with this condition may be taller than average and may experience learning difficulties or behavioral problems. Approximately 1 in 800 girls will be born with an extra X chromosome.

Boys with Jacob’s syndrome have an extra Y chromosome (XYY). Most babies with XYY syndrome do not have any birth defects. Boys with XYY may be taller than average and have an increased risk for learning, speech, and behavioral problems. Approximately 1 in 650 boys will be born with an extra Y chromosome.