NTD Laboratories, Inc.
403 Oakwood Road
Huntington Station, NY 11746
Phone: 1.888.NTDLABS (683.5227)
ntdlabs@perkinelmer.com
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NTD Laboratories, Inc.
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Pregnant women are advised that the information provided here is of a general nature and is intended to provide a better understanding of the prenatal screening process. All medical decisions should be made in consultation with a licensed physician or other professional healthcare provider. For more information, click on one of the subject headings on the left.
Down Syndrome, also known as Trisomy 21, is a genetic disorder resulting when the 21st pair of chromosomes in the body's cells has an extra, or third chromosome, instead of the usual two chromosomes. Having an extra chromosome is called a "trisomy". This condition affects development, causing birth defects.
Most individuals have a total of 46 chromosomes arranged in 23 pairs. These 23 pairs are numbered 1-22 and the 23rd pair, designated as XY determines the sex of the baby. Chromosomes control growth and development and are considered as transmitters of genetic material. Chromosomal imbalance, as in trisomies results in problems with developmental growth.
The degree of physical and mental retardation for individuals affected by Down Syndrome varies greatly. For some it is minimal; for others it is substantial. Chromosomal imbalance often leads to a combination of malformations, which may include flattened facial features and retardation of both physical and mental growth. All Down Syndrome individuals have some degree of mental impairment. Congenital heart disease, a major cause of early death frequently associated with Down Syndrome, may be corrected by surgery. Recently advances have been made in improved education for Down Syndrome children. Down Syndrome occurs in about 1 in 800 births, however the incidence rate varies significantly by age.
Trisomy 18 is another type of chromosomal abnormality in which the 18th pair of chromosomes has an extra or third chromosome instead of the usual two chromosomes. Trisomy 18 is a more severe disorder than Down Syndrome. Approximately 30% of babies die within the 1st month of birth, 50% by 2 months, 70% by 3 months, 90% by 1 year of age and 99% by age 10. The survivors are profoundly retarded in both physical and mental growth. None have been able to walk, or talk. Trisomy 18 occurs in 1 out of every 6,600 births.
Open neural tube defects are birth defects which affect the head and spine of the baby. They occur when the neural tube (the structure that later develops into the brain and spinal cord) remains open instead of closed during embryonic growth in the first month of pregnancy.
Anencephaly (an-en-sef-a-lee) is a disorder in which much of the brain and head are underdeveloped. Newborns usually do not survive after birth. Anencephaly occurs in 1 out of 1,500 pregnancies but incidence rates vary by geography and ethnicity.
Open spina bifida involves an opening in the spine (backbone) of the baby. Open spina bifida is often accompanied by several handicaps with varying degrees of severity including paralysis of the legs, lack of bowel or bladder control and an accumulation of excess fluid in the brain. In a small percentage of open spina bifida newborns, the birth defect is minor. Open spina bifida occurs in about 1 out of 2,000 pregnancies but incidence rates vary by geography and ethnicity.
Closed spina bifida is a defect of the spine which is covered by skin or membranous tissue. The closed form of spina bifida may lead to handicaps and is rarely detectable by prenatal screening.
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