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Genetic Counseling & Testing Services
Genetic ScreeningScreening refers to various testing strategies used for the detection of babies at increased risk for a particular disorder. In pregnancy, screening is available for several genetic and chromosomal conditions, such as Cystic Fibrosis and Down syndrome, respectively. Traditionally, maternal age has been used as the primary screening tool in determining which babies were at increased risk for chromosomal abnormalities, such as Down syndrome. However, with new screening tools that have better detection rates and lower false positive rates, maternal age is no longer considered the “gold standard”. In January 2007, the American College of Obstetrics and Gynecologists (ACOG) released new guidelines recommending that all women, regardless of age, be offered screening as well as diagnostic testing options. Screening and diagnostic testing in pregnancy is always optional. Importantly, women must understand the differences between screening and diagnostic testing options in pregnancy. At MFMCP, the woman has a consultation prior to any screening or diagnostic test with a certified genetic counselor. During the brief consultation, the woman is informed of all her choices, the limitations and possible risks associated with various tests, and the possible outcomes of the test results. An informed decision is necessary, and the woman’s informed consent is required for screening and diagnostic testing at MFMCP. First Trimester Combined ScreeningBetween the 11th and 14th week of pregnancy (11wks 1day to 13wks 6days) a fetal ultrasound (nuchal translucency measurement) and maternal blood work can be performed to detect over 90% of babies with Down syndrome and Trisomy 18/13. MFMCP is one the few centers in central Pennsylvania certified to perform NT measurements. MFMCP Frist Trimester Screening BROCHURE Second Trimester Maternal Serum ScreeningTypically performed between 16 and 20 weeks of pregnancy, maternal serum screening detects about 70-80% of babies at risk for Down syndrome and Trisomy 18. Referred to as the triple screen or the quad screen, part of second trimester serum screening involves measurement of alpha fetoprotein (AFP) levels in maternal blood. This protein screens the pregnancy for spina bifida (an open defect in the development of the fetal spine). Women who undergo first trimester combined screening can also opt to pursue spina bifida screening in the second trimester. These women do not repeat screening for Down syndrome and Trisomy 18. Ultrasound Markers At around 20 weeks (5 months) of pregnancy, a fetal ultrasound is recommended to all Chorionic Villi Sampling (CVS)Procedure to obtain pieces of placental tissue that can be used for genetic testing and chromosomal analysis. This diagnostic test is performed between 10-13 weeks of pregnancy. At our office, CVS is performed by placing a small catheter through a woman’s abdomen under ultrasound guidance, and a small tissue sample of placenta is collected. The risk of complications after a CVS is less than 1 in 100 (1%). AmniocentesisProcedure to obtain amniotic fluid that can be used for genetic testing, analyzed for infection, or used to check baby’s lung maturity. Typically, this diagnostic test is performed between 15-21 weeks of pregnancy. In addition to third trimester amniocentesis to evaluate fetal lung maturity, we also perform third trimester amniocentesis for genetic diagnosis and chromosomal analysis. The risk of complications after an amniocentesis is less than 1 in 200 (o.5%). Percutaneous Umbilical Sampling (PUBS)
Sampling of the baby’s blood via the umbilical cord while still in utero that can be used for genetic testing and diagnosis of hematic diseases. In some cases, direct treatment of the baby for certain hematic diseases can be performed during pregnancy. Carrier Screening For Common Inherited DisordersIn certain ethnic backgrounds some inherited conditions are more common than others. A negative family history of the disease(s) does not mean there is no risk to the pregnancy. Most of these genetic conditions are inherited in an autosomal recessive manner, meaning that an affected individual inherited a copy of the disease-causing gene from both Mom and Dad. Parents are usually healthy and do not have the actual condition, rather they are referred to as “carriers”. Each child born to two carrier parents has a 1 in 4 (25%) chance to be affected with the disease. The American College of Obstetrics and Gynecologists (ACOG) recommends that individuals of certain ethnic groups be offered carrier screening for different genetic conditions.
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women to look at fetal anatomy. In addition to routine measurements, the internal structures of the baby (heart, brain, kidneys, etc) can be seen in detail to rule out most major physical defects. Some physical birth defects are associated with an increased risk for a chromosomal condition, such as Down syndrome. Furthermore, subtle changes or differences noted on ultrasound can also be associated with an increased risk for a chromosomal abnormality. These subtle physical changes or differences, referred to as minor markers, are usually only associated with an increased chromosome risk if other risk factors are also present. These other risk factors include maternal age over 35 years, abnormal screening, or other ultrasound findings. Examples of minor ultrasound markers are choroid plexus cysts (CPCs) and echogenic intracardiac foci (EIFs)
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