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KMID : 0377619960610040291
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Korean Jungang Medical Journal
1996 Volume.61 No. 4 p.291 ~ p.297
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Prenatal Diagnosis of Genetic Disorders
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Cho Sechin
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Abstract
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Prenatal diagnosis of genetic disorder has been the most significant advancement in clinical medicine.
Major birth defects complicate and threaten the lives of 2.8 percent of newborn infants. Serious genetic disorders account for 20 percent of deaths during newborn and infancy.
The information gathered from prenatal diagnosis may be helpful to the obstetrician in the management of pregnancy, labor and delivery. The prenatal diagnosis may improve the outcome of pregnancy. The availability of prenatal diagnosis gives couples options that they might not otherwise have. This enables couples to have children, who, without this information, might have been unwilling to attempt the pregnancy.
Indications for Prenatal Diagnosis
The identification of a pregnancy in which there is an increased risk for a diagnosable fetal disorder involves searching for general and specific risk factors. It is standard practice to offer prenatal cytogenetic diagnosis to all women who will be 35 years of age or older at the time of delivery (Advanced Maternal Age). Maternal serum alpha fetoprotein or triple marker screening identifies patients at risk for certain cytogenetic and structural abnormalities. Open neural tube defects and ventral wall defects are associated with increased level of alpha fetoprotein in both amniotic fluid and maternal serum.
Specific risk factors may be identified in the family history, history of previous pregnancy or the mother´s medical history. Prenatal diagnosis is possible for many inborn metabolic disorders. Maternal diabetic mellitus and PKU are associated with certain fetal malformations. Known teratogens include ionizing radiation, therapeutic and illicit drugs and maternal infections. Finally, gene frequency differs among population groups depending on the basis of ethnic and racial background. As ultrasonography is more readily available, fetal abnormalities identified by this procedure may indicate further prenatal diagnosis.
Chromosomal Analysis
Fetal chromosomal analysis should be offered when any of the following apply
1. The mother is 35 years old or older at time of delivery.
2. There is a previous offspring with one of the trisomic syndromes or other chromosome
aberrations. potentially teratogenic agent ; (3) family history of congenital heart defects, particularly in a parent or sibling ; (4) suspected fetal chromosome abnormality or genetic disease associated with heart defects ; (5) maternal diseases associated with fetal structural heart defects, such as diabetes or PKU, or maternal diseases associated with fetal cardiac arrhythmia, particularly heart block, such as lupus or other immune disorders ; or (6) suspected cardiac defects based on the findings of routine ultrasound.
New Horizon
The Human Genome Project (HUGO) is expected to be completed in the year 2005. The cost effective screening is expected for many disorders which are not available currently. Preimplantation genetics are available in certain circumstances and may allow fetal treatment before organogenesis. Increasingly fluorescence in situ hybridization (FISH) for specific chromosomes is being used to define chromosomal rearrangement including deletion and microdeletions that may be below the sensitive detection by standard genetic analysis. FISH to interface nucleotides being investigated as a rapid screen method aneuploidy.
A promising new technique for fetal isolation from maternal blood is being studied. This technique one day will make non-invasive prenatal diagnosis a reality.
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