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Prenatal Diagnosis PowerPoint Presentation

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Published on : Mar 27, 2023 | Views : 1960 | Downloads : 0

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By Dr. Shumaila Zia Assistant Professor PRENATAL DIAGNOSIS
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Prenatal Diagnosis Over the last 4 decades, the genetic basis of an increasing number of diseases is becoming understood. At the same time, safe and effective fetal diagnostic techniques are being developed.
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Fetal medicine Only in the past few decades has the fetus been considered a patient and become the subject of extensive scientific study and attempts at treatment. Fetal medicine is a complex multidisciplinary undertaking with a team Fetal diagnosis Fetal Therapy
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Prenatal Diagnosis of fetal Abnormalities Benefits: Malformation incompatible with life may be terminated. Certain abnormalities may be correctible in-utero. -Provides opportunity to arrange corrective measures before hand. - offer a chance to be delivered at a place where the required facilities are available. 4. Parents decision to continue pregnancy/ mentally prepare to have a handicapped child.
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Classification of Congenital Abnormalities Chromosomal Abnormalities: - Trisomy 21 (D.S) - Trisomy 18 (E.S) - Trisomy 13 (P.S) Structural Abnormalities: - CNS - CVS - GIT - Bone - Renal system Genetic Disorders: - Inborn error of metabolism - Haemoglobinopathies
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What Should We Do? Every pregnancy should be evaluated with the most definite test. Practically & economically not feasible because expensive Invasive Worldwide practice is to carry out -Screening procedures -Definite (diagnostic)tests for screening positive cases
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Screening Procedures These are: - Simple - Cheap - Least invasive - safe - Easily repeatable
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Screening Procedures --- Cont. History: - Increasing maternal age - Congenital anomalies in previous children - F/Hx. . Still birth . Recurrent 1st trimester abortion . Cousin marriage
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Screening Procedures ---Cont. 2. Features of current pregnancy: - Drug intake(antiepileptics e.g. warfarin, alcohol, smoking) - Radiation exposure - Maternal ch. diseases e.g.DM, cardiac, renal - Uterine fundas large/ small for date - Decrease fetal movements - Fetal malpresentation - Viral infection in early pregnancy
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Screening Procedures --- Cont. 3. Ultrasonography: - Screening tool in all trimesters - At 10-14 weeks if fetal nuchal translucency - > 2.5 mm- chromosomal anomalies association - At 18-20 weeks 75% fetal abnormalities can be diagnose
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1st Trimester Ultrasound NT Ultrasound
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Cleft lip and palate
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Ventriculomegaly
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Posterior Urethral Valve
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Multicystic Dysplastic kidney
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Multicystic Dysplastic kidney
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Screening Procedures ---Cont. 4. Maternal blood tests: - Maternal Serum alpha fetoproteins: . Produced by . Fetus &enter in maternal circulation. . Yolk sac in first trimester . Liver in second and third trimester . Normally increase from 12-32 weeks . Abnormally raise on fetal capillaries exposure to amniotic fluid e.g. in NTD.
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Maternal S. alpha fetoproteins --cont. - Raised level in neural tube defect(NTD). - Screen for NTD at 15-20 weeks if +ve confirm with detailed USG. - Also raised in following conditions: . Miscalculated dates . Multiple pregnancies . Threatened abortion . IUD . Teratoma . Congenital nephrosis . Ant. Abdominal wall defects
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MSAFP
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Triple Test - Used for Down Synd. Screening. It comprises . AFP . hCG . uE3 (unconjugated oestriol ) - Best carried at 15-18 weeks. In DS AFP & uE3 are low while hCG is raised - Triple test+ maternal age diagnose 60% DS - In trisomy 18 all above components are low
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Quadruple test Triple test+ Inhibin A estimation This test + maternal age detects 76% DS
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Double Test Low pregnancy associated plasma proteins-A (PAPP-A) level and raised serum Beta-hCG during 1st trimester Double test+ maternal age diagnose 60% DS.
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DIAGNOSTIC TESTS For high risk women on basis of screening tests An ideal test should be : - Least invasive - diagnose c. abnormality in early pregnancy. - Minimally interfering developing pregnancy Diagnostic tests are also not risk free.
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Counselling Organize an appointment Couple should be present Explain: - Risk of occurance of c. abnormality - All tests available, their procedure, cost, diagnostic ability and benefits, possible risks - Possible management plain If termination of pregnancy is unacceptable diagnostic tests would be fruitless.
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NON INVASIVE TESTS Ultrasonography: Diagnostic USG is different from screening USG, - It takes longer time - Dx. Wide range of c. anomalies - Non invasive and diagnosis at spot possible - But possible only at large gestational age Colour doppler further enhance the capability especially for cardiac malformations and renal agenesis.
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Other Soft Signs short ears cerebellar hypoplasia cholecystomegaly Mild cerebral ventriculomegaly Hypoplasia of middle phalanx of 5th digit Increased Iliac angle Short frontal lobe
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What are the 2T soft signs? Increased nuchal thickness short femur or humerus Pylectasis echogenic foci in heart Echogenic Bowel choroid plexus cysts
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INVASIVE TESTS AMNIOCENTESIS: Aspiration of amniotic fluid which contain fetal cells Fluid can be used for estimation of - bilirubin level (for fetal haemolytic disease). - AFP -Acetyl cholinesterase Cells used for karyotyping (Chromosomal dis.) Fetal cells-cultured for 3 weeks- karyotyping. New technique-PCR, FISH-give result in 48 h. Preferred time of test 16weeks of pregnancy.
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AMNIOCENTESIS---Cont. Procedure: Preliminary USG to confirm-duration of gestation, -placental site,- adequacy of liqour (150-200 ml) Sterilize the abdomen 22 G spinal needle is used. About 20 cc amniotic fluid is withdrawn. Give Anti- D to all Rh-ve mothers. Ask rest for 30 min.& restrict movements for 48h
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Amniocentesis
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AMNIOCENTESIS---Cont. Limitations (difficulties)of procedure: if - Anteriorly placed placenta - Multiple pregnancy. - Maternal obesity - Oligohydramnios Risks: - Pregnancy loss 1 % - Bleeding , Infection, - Rupture of membrane - Preterm labour&IUD - Leaking of Amniotic fluid - Increase risk of RDS in newborn
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CHORIONIC VILLUS SAMPLING Collection of fragments of placental tissue (chorionic villi)- cells are examined for Dx. of C.Anomalies. Cytotrophoblastic (rapidly dividing) cells are used for direct karyotyping- result available within 24-48 h. Chorionic villi are best source of DNA CVS can be performed at 10 weeks gestation. Indications: 1-DNA analysis for SCD,thallasemias, CF. hemophillias 2-Chromosomal abnormalities 3-Inborn error of metabolism
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CHORIONIC VILLUS SAMPLING Procedure: Trans-abdominal approach preferred –under USG guidance in supine position Trans-cervical approach is easy. In lithotomy position, sterilize area & Aspiration catheter and biopsy forceps. Introduce through Cx. under USG into placental tissue avoiding membrane rupture Risks: Pregnancy loss 2-6% Before 10 weeks- associated with limb deformities, micrognathia, microglassia
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FETAL BLOOD SAMPLING (FBS) Fetal blood- lymphocyte are rapidly cultured, results within 48-72 hours. Indications: 1- Prenatal Dx. DNA available for Cytogenetic studies In failed amniocentesis, and mosaicism in chorion or amniotic fluid. 2-Fetal assessment: for red cell alloimmunization, (Hb;Hc,TrF) Hydrops fetalis, viral infection, platelets alloimmunization Unfortunately Associated with highest rate of fetal loss. Currently used for blood transfusion in-utero in fetal A.
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FETAL BLOOD SAMPLING (FBS) Procedure : (cordocentesis): The sites for FBS are placental insertion of umbilical cord, abdominal insertion of cord, intrahepatic fetal vein and fetal heart. Suitable time is 20-28 weeks Risks: - Bleeding from site of puncture - Cord haematoma - Fetal bradycardia - Fetal death
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EMBRYOSCOPY & FETOSCOPY Direct visualization of embryo and fetus. Limited field of vision. Provide information only about external fetal structures .
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NEW MOLECULAR ANALYTIC TECHNIQUES Fetal cell obtained by CVS and Amniocentesis can be used for prenatal Dx. For congenital anomalies by following new techniques 1- Southern blotting: Cleavage of chromosomal DNA at specific sites and used for tests 2- PCR 3- FISH
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Polymerase chain reaction (PCR) Amplify specific DNA and RNA fragments Once nucleotide sequence of a region of DNA strand is known, complimentary oligonucleotides & polymerase are added to single strand DNA Repeat process 30 times to get adequate DNA PCR identify specific DNA sequence for gene mutation & prenatal Dx. at an earlier stage before an embryo transfer in IVF cycle.
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FLOURESCENT IN SITU HYBRIDIZATION FISH allows detection & localization of specific DNA sequence in interphase or metaphase. Advantage – results available in 24-48 h. Disadvantage – fail to detect big structural rearrangements Identify 80% clinically relevant abnormalities, helpful for early decision about further management of affected pregnancies.
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MANAGEMENT OF FETAL C. ANOMALIES It is a tedious task, requires skillful, sympathetic & professional approach. Management options - Termination of pregnancy - In- utero management if possible - Conservative management
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POSTPARTUM MANAGEMENT OF C.A. For better understanding of congenital anomalies and its impact on future reproductive performance of couple, following procedures are carried out on affected babies/ abortusses: Physical examination /postmortem Fetal tissue(blood, skin, placenta) for karyotyping Placenta and membrane for histopathology Placental & baby swab for microbiology & virology. Baby gram (x-rays of whole baby) Baby photograph
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THANKS