Prenatal Diagnosis PDF 2022

Prenatal diagnosis & genetic Counseling Dr.Khalida Hassan Muho Specialist OB\GYN  The aim The aim is related to identification of fetal abnormalities in :order to 1-Re assurance of parents by reducing the undiagnosed fetal abnormality. 2-maximize the information ava...

Prenatal diagnosis & genetic Counseling Dr.Khalida Hassan Muho Specialist OB\GYN  The aim The aim is related to identification of fetal abnormalities in :order to 1-Re assurance of parents by reducing the undiagnosed fetal abnormality. 2-maximize the information available to parents if fetal abnormality is detected. 3-allow the parents decision making rents of pregnancies in which abnormality is identified to prepare for the birth of the child if they decide to continue with the pregnancy. 4-enable parents at risk to inherited conditions to have healthy children by diagnosis of abnormality & termination of affected fetuses. 5-allow appropriate prenatal management & intrauterine treatment  Test for fetal abnormality are two :Screening (which is not diagnostic ) tests -1 To enable the selection of pregnancies to which diagnostic test can be applied, allowing for the early detection at early stage, for appropriate.prenatal management or termination of pregnancy Diagnostic test: Done on high risk pregnancies-2. that been identified by prior screening test Prevalence of congenital abnormalities Prenatal screening & Diagnostic Test Cordocentasis Invasive diagnostic Test Laboratory analysis Samples from fetal origin will send to the following ;investigations as 1-Cytogenetic analysis: ; the fetal cell will examine for chromosomes DNA analysis; Fetal DNA obtained used for-2 ,DNA probing (sickle cell disease & cystic fibrosis)-1 PCR (fragile X syndrome, congenital toxoplasmosis, CMV)-2 Linkage analysis (fragile X syndrome)-3.Biochestercal & Enzymatic analysis-3 This perform when DNA analysis is not possible for specific diseases (congenital adrenal hyperplasia &.mucopolysacchridosis)  Cytogenetic analysis-1 Cells obtained from invasive prenatal. procedure ;The times for diagnosis are Amniocentesis; 2-3wks-1 Chorion villus sampling; 1-2wk-2 3-Cordocentasis 24-48h  Cytogenetic analysis-1 ;Chorionic villus sampling The cells already in mitosis so that a direct result may.available It can detect aneuploidy (abnormal in no.). This test is not sufficient for G-banding (chromosomal aberrations such as deletions, or invasion cannot be excluded). FISH test can facilitate rapid results with amniocentesis. FSH test detect & localize specific DNA sequences directly in interphase or metaphase. It allows the rapid (24-48hs) prenatal diagnosis of major.aneuploidies for chromosomes 13,18, 21& XY General process of steps required for preimplantation genetic diagnosis and preimplantation genetic screening Removal of blastomere from an 8- cell embryo (cleavage-stage.embryo)  Structural abnormalities These constitute the majority of congenital abnormalities , established screening programs for fetal neural tube & cardiac defects. The Royal college of obstetric & gynecology advised two stages scan for screening Programm for.structural abnormalities ;Two stages & An initial scan at booking (11-14wks) -1.At or around 20wks -2  Neural tube defects (NTDs)-1 NTDs among the most common major abnormalities which occur due to defect in the formation of the. neural tube during embryogenesis ;Aetiology: multi-factorial as. Environmental-1. Genetic-2 Pharmacological-3. Geographical factors-4 cranial vault  NTD Types that affects cranial vault present on USS NTD by (USS)  Prenatal screening & diagnosis of NTD When a parent or previous sibling has had an NTD the risk of recurrence is 5-10%. Screening test: Mid-trimester maternal serum Serum alpha-fetoprotein (AFP) levels are increased in pregnancies affected by open NTD type. Diagnostic test of open NTD: Acetylcholinesterase being used So, Positive AFPs ….. the case referred for amniocentesis for presence of acetylcholinesterase (a central nervous system neurotransmitter) in amniotic fluid Prevention of NTDs  Congenital heart disease Atiology ; Genetic ,environmental ,& viral infection. Prenatal screening required for women with ; ,A previous sibling or father is affected by CHD risk 2%-1 If two siblings or the mother have CHD, the recurrence risk -2. is 10%.Mother type 1 D.M. the risk is double (20%) -3 Cases of CHD 90% are form pregnancies with no such risk.factors ;Prenatal diagnosis USS at 20 weeks of gestation echocardiography done in.special centers in selected cases GIT-3  Abdominal wall defect Omphaloceles Talipes equinovarus-2 (clubfoot) Renal Others Chromosomal abnormalities Aneuploidies ( usually trisomies ) Trisomies mainly due to non-disjunctions in meiosis which.is usually associated with maternal advancing age.Rarely due to unbalanced translocations or mosaisim Majority of trisomies are result in first trimester a abortion except.for trisomies 13 (Patau s) ,18 (Edward s) ,& 21(Downs) Trisomies 13 &18 are lethal because are associated with.major structural anomalies that can be detect by USS Screening program js require for antenatal diagnosis of Downs syndrome which is the commonest.chromosomal abnormality at birth  Sex chromosome abnormalities Sex chromosome no relation with maternal age: 1-Turner syndrome (monosomy X or 45XO). infertile females of normal intellect & short stature. 2-Klinefelter s (47XXY) are infertile male slightly reduced IQ ,testicular dysgenesis & tall stature. Routine screening not available The diagnosis is often made.incidentally Turners syndrome Klinefelter s (47XXY)  Fragile X  This is the most common inherited cause of male mental retardation.  Prenatal diagnosis is by PCR.  analysis only for male fetus for detection fragile X gene (FMR1).  The prenatal screening only for families in which one of the parents is known to be a carrier. Screening test for Down syndrome; XO Maternal age & history  Screening tests for syndrome Downs ; A-Matrenal age & history above 35 yrs old risk is 75-80%, should be [email protected] test. patient who give birth of baby of down @ B-Maternal serum biochemistry , First trimester screening uses two markers;.PAPP-A which is lowered in D.S-1. Beta –HCG which Is elevated -2 maternal age provide an individual ,in a similar fashion to 2 nd trimester & biochemical screening. 2nd trimester (15-22whs gestation) AFP is increase & HCG is increase, in this syndrome Logarithm predicts the individual risk for D.S. This is not diagnostic, but identify a group at high risk (1:250) who shd be offered a diagnostic test as amniocentesis. C-Uss NT (nuchal thickness);10-15wks combination NT=G.A, Alogharthm -1 predict individual risk this similar as other uss anomalies-2  Genetic disorder 1-Cystis fibrosis; Autosomal recessive condition & lethal genetic disorder A gene which isolated to long arm of chromosome 7 Prenatal diagnosis is offered to parents who are known carrier, usually because they have already had a affected children. 2-Haemoglobinopathy; Thalassemias & sickle cell disease. Autosomal recessive. Carrier are high as 20%in Africa & in Mediterranean populations. Screening at risk –HB electrophoresis.. Prenatal diagnosis done for prerequisite by fetal DNA. As the risk of an affected pregnancy is high (25%) for carrier parents early testing by CVS is advocated.  Congenital viral & parasitic infection This is infrequent  New development Fetal cell in maternal circulation-1 Pre-implantation genetics diagnosis-2 three dimensional USS -3 Fetal magnetic resonance imaging;-4 Overcome fetal movement artifact Thank you