Down's syndrome, also known as Trisomy 21, is a genetic disorder caused by the appearance of an extra (third) chromosome 21 instead of just two chromosomes. Normally, each person has 23 pairs of chromosomes with each chromosome in a pair coming from each parent. Fertilization between an affected egg and sperm leads to an abnormal division of chromosomes resulting in a fertilized embryo with 47 chromosomes (46 plus the extra copy of chromosome 21). In the majority of cases, the abnormal cell division affects all the tissues in the body. When the trisomy 21 is present in some but not all cell lines, the variant is called 'Mosaic Down Syndrome' which is associated with less developmental delay than a full trisomy 21.
Down's syndrome is a relatively common birth defect. It occurs in approximately 1 in 150 conceptions. Rates of Down's syndrome increase with maternal age. Accepted incidence of 1 in 1,250 at age 25, increases to 1 in 1,000 at age 30, to 1 in 400 at age 35, to 1 in 100 at age 40 and 1 in 35 at age 45. Diagnosis of Down's syndrome can be made early during a pregnancy to allow the parents to determine whether would prefer to carry the pregnancy to term. Down's syndrome is associated with a number of major disorders which include:
Individuals with Down's syndrome have some characteristic which include:
Flattened facial profile
Low nasal bridge
Mild to moderate mental retardation
Historically, screening for Down's syndrome was reserved for women age 35 or older at the time of birth. In reality, because younger women have more babies, 80% of babies born with Down's syndrome are born to mothers younger than 35 yeas of age at birth. The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women, regardless of their age, be offered screening for Down's syndrome. Prenatal screening for Down's syndrome include:
Ultrasound (nuchal translucency)
Tests of serum markers (blood tests)
Screening ultrasound evaluation of a fetus for physical traits of Down's syndrome is performed during the first trimester of pregnancy. A sonolucent area in the back of the neck is usually present in the third trimester of pregnancy. Measurement of this clear fold of tissue behind the baby's neck by ultrasound between 11 and 14 weeks of gestation should be less than 3 mm. Any increase in nuchal translucency greater than 3 mm indicates that the risk of some genetic disorder, including down's syndrome, is increased.
Another screening test involves the measurement of some substances in the maternal blood along with maternal age and gestational age. These tests have to be performed between 15 and 22 weeks of gestation to increase the validity of the results. Measurement of alpha fetoprotein (AFP), human chorionic gonadotropin (hCG) and unconjugated estriol (uE3) is known as 'Triple marker'; the addition of the measurement of inhibin A increased the accuracy of the results and is called "Quadruple marker'.
Like all screening tests, results must be cautiously interpreted and confirmed by additional diagnostic testing. A diagnostic tests are used to confirm or rule out a chromosomal abnormality, including Down's syndrome. Diagnostic tests include:
Chorionic villus sampling (CVS)
Percutaneous umbilical blood sampling (PUBS)
Chorionic villus sampling (CVS) is performed between 8 and 12 weeks of gestation. Amniocentesis is performed between 16 and 20 weeks of gestation. Percutaneous umbilical blood sampling (PUBS) is performed after 20 weeks of gestation. The American College of Obstetricians and Gynecologists (ACOG) also recommends that women of all ages have the option to bypass screening and choose a diagnostic test for Down's syndrome.
If your child suffers from Down's syndrome (trisomy 21) and you were not given the option to undergo screening, genetic counseling and/or genetic testing, Dr. Borten and the Boston area medical malpractice attorneys at Gorovitz & Borten can help you assert your rights and get the compensation you deserve.
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