Prenatal diagnosis

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Prenatal diagnosis

  1. 1. Prenatal Diagnosis Asheber Gaym M.D. January 2009
  2. 2. Outline • Definition of prenatal diagnosis • Indications of prenatal diagnosis • Methods of prenatal diagnosis • Interventions following prenatal diagnosis 2Asheber Gaym,2009
  3. 3. Definition of prenatal diagnosis • Prenatal diagnosis refers to procedures undertaken to diagnose genetic abnormalities and structural anomalies of the early embryo and fetus in order to undertake timely parental counseling and appropriate interventions • Prenatal diagnostic techniques allow early diagnosis of fatal genetic and structural anomalies for timely termination of pregnancy thereby preventing pregnancy wastage and perinatal mortality • Prenatal diagnostic techniques require the concerted efforts of the obstetrician, geneticist and genetic counselor to reach to the correct diagnosis and intervention 3Asheber Gaym,2009
  4. 4. Indications for prenatal diagnosis • Maternal age greater than 35 • Past history of delivery of a malformed fetus • Past history of delivery of a genetically abnormal fetus • Family history of genetic diseases • History of genetic disease in either parent • Exposure to potential teratogens early in pregnancy 4Asheber Gaym,2009
  5. 5. Methods of Prenatal Diagnosis Methods Procedure Advantages and Risks Chorionic villous sampling Transcervical or tranabdominal aspiration of trophoblastic tissue for karyotyping and genetic studies in pregnancies less than nine weeks Early diagnosis and timely termination of pregnancy. 3% abortion risk. Genetic amniocente sis Aspiration of amniotic fluid under ultrasound guidance and culture and karyotyping of amniotic cells. Early - < 11 weeks; Late – 16-18 weeks Early diagnosis and timely termination of pregnancy. 3% abortion risk. RH Isoimmunization. Routine ultrasonogr aphy Performed at 16-18 weeks or earlier to diagnose structural anomalies of the early embryo-fetus Allows second trimester termination of pregnancy In vitro fertilization Cell taken from the earliest morula for karyotyping Allows termination of the implantation if abnormal Percultane ous umbilical blood sampling PUBS refers to transabdominal aspiration of fetal blood from the umbilical vein for detailed analysis of fetal diseases by performing hematological, genetic, immunological etc fetal diseases Allows the diagnosis of numerous fetal diseases 5Asheber Gaym,2009
  6. 6. Methods of Prenatal Diagnosis Method Procedure Advantages and Risks Fetoscopy Detailed inspection of fetal anatomic structures and biopsy through a fiberoptic device inserted into the uterus through the abdominal wall Risk of abortion is very high. This procedure has been superseded by the less invasive methods such as CVS and amniocentesis. Examples of genetic anomalies diagnosed by prenatal diagnosis include trisomies 13,18,21; monosomy X ( Turner’s syndrome); Klienfelter’s syndrome; phenylketonuria; Gauscher’s disease … etc Examples of structural anomalies diagnosed by prenatal diagnosis include anencephaly, hydrocephalus, encepalocele, phecomelia, gastroschissis … etc 6Asheber Gaym,2009
  7. 7. Management of abnormal prenatal tests • Factors important in the decision include: – Survival chance of the fetus with the identified genetic or structural abnormality – Available treatment options if any – Expected life expectancy with the abnormality • With the above information, detailed counseling with both parents is conducted • Final decision is reached by the parents and either continuation of pregnancy or termination of pregnancy is undertaken 7Asheber Gaym,2009

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