Prenatal Diagnostic Tests PDF

Chapter 15 Prenatal Diagnostic Tests Copyright © 2018 Elsevier Inc. All rights reserved.  Assessment of Patient Who Has Diagnostic Testing ˜ Gravida, para, living children, gestation ˜ Maternal health problems ˜ Current obstetric problems ˜ Prior obstetric problems ˜...

Chapter 15 Prenatal Diagnostic Tests Copyright © 2018 Elsevier Inc. All rights reserved.  Assessment of Patient Who Has Diagnostic Testing ˜ Gravida, para, living children, gestation ˜ Maternal health problems ˜ Current obstetric problems ˜ Prior obstetric problems ˜ History of substance abuse, including alcohol and tobacco ˜ Patient understanding of test and reasons for it ˜ Patient knowledge of surveillance regimen for additional testing ˜ Patient’s emotional response to test ˜ Patient’s and partner’s expectations of test Copyright © 2018 Elsevier Inc. All rights reserved. 2  Types of Prenatal Tests 1. Ultrasound 2. Doppler ultrasound blood flow assessment 3. Alpha-fetoprotein (AFP) screening 4. Multiple marker screening 5. Chorionic villus sampling 6. Amniocentesis 7. Percutaneous umbilical blood sampling 8. Antepartum fetal surveillance a) Nonstress test (NST) b) Vibroacoustic stimulation test c) Contraction stress test (CST) d) Biophysical profile (BPP) e) Modified biophysical profile 9. Maternal assessment of fetal movement Copyright © 2018 Elsevier Inc. All rights reserved. 3  Ultrasound ˜ Used to determine a variety of fetal and placental conditions Ø Presence and location of pregnancy Ø Multifetal gestation Ø Gestational age Ø Viability confirmation Ø Identifying fetal abnormalities ˜ Emotional responses ˜ Not always possible to determine fetal sex Copyright © 2018 Elsevier Inc. All rights reserved. 4 2D Sonogram Copyright © 2018 Elsevier Inc. All rights reserved. 5 3D Ultrasound Image Copyright © 2018 Elsevier Inc. All rights reserved. 6  Doppler Ultrasound Blood Flow Assessment ˜ Ultrasound is used to perform the test. Ø Doppler shift ˜ Used in pregnancies complicated by Ø Hypertension Ø Fetal growth restriction Ø Placental insufficiency ˜ Measures systolic to diastolic ratio Copyright © 2018 Elsevier Inc. All rights reserved. 7 Color Doppler Imaging Umbilical Vein and Two Arteries Copyright © 2018 Elsevier Inc. All rights reserved. 8  Alpha-Fetoprotein Screening ˜ AFP assessment is performed on maternal serum or amniotic fluid to identify Ø Open body wall defects (neural tube defects) Ø Chromosomal anomalies (trisomy 21) ˜ Ideally performed between 16 and 18 weeks of gestation ˜ Requires only a blood sample ˜ Must be viewed as a first step in screening Copyright © 2018 Elsevier Inc. All rights reserved. 9  Multiple Marker Screening ˜ Two other markers have been added Ø Human chorionic gonadotropin (hCG) Ø Unconjugated estriol ˜ Increases the detection of trisomy 18 and 21 ˜ If testing is positive Ø Amniocentesis is recommended. Copyright © 2018 Elsevier Inc. All rights reserved. 10  Chorionic Villus Sampling ˜ Uses transcervical or transabdominal sampling to obtain villi ˜ Can be performed much earlier than amniocentesis ˜ Provides information about numerous chromosomal defects, metabolic or DNA abnormalities ˜ Performed between 10 and 13 weeks’ gestation Copyright © 2018 Elsevier Inc. All rights reserved. 11 Transcervical Chorionic Sampling Copyright © 2018 Elsevier Inc. All rights reserved. 12  Amniocentesis ˜ Aspiration of amniotic fluid from the sac for further examination ˜ Second trimester amniocentesis Ø Performed between 15 and 20 weeks Ø Chromosomal or biochemical abnormalities ˜ Third trimester amniocentesis Ø Performed during the third trimester Ø Used to determine fetal lung maturity or hemolytic disease Copyright © 2018 Elsevier Inc. All rights reserved. 13 Indications for Second Trimester Amniocentesis Copyright © 2018 Elsevier Inc. All rights reserved. 14 Amniocentesis Copyright © 2018 Elsevier Inc. All rights reserved. 15  Percutaneous Umbilical Blood Sampling ˜ Also called cordocentesis or PUBS ˜ Involves the aspiration of fetal blood from the umbilical cord near the placenta for prenatal diagnosis or therapy ˜ Used to detect blood disorders, acid–base imbalance, infection, or fetal genetic disease Copyright © 2018 Elsevier Inc. All rights reserved. 16 Percutaneous Umbilical Cord Testing Copyright © 2018 Elsevier Inc. All rights reserved. 17  Antepartum Fetal Surveillance ˜ NST Ø NST evaluates fetal heart rate (FHR) accelerations, with or without fetal movement. Ø FHR reactivity with accelerations is a reassuring sign. Ø Reactivity is associated with adequate fetal oxygenation and intact neural pathways. Ø FHR reactivity may not develop until 32 weeks in the fetus. ˜ Vibroacoustic stimulation Copyright © 2018 Elsevier Inc. All rights reserved. 18 Nonstress Test Copyright © 2018 Elsevier Inc. All rights reserved. 19  Antepartum Fetal Surveillance ˜ CST Ø Oxytocin challenge test Ø Used to determine how the fetal heart responds to uterine contractions that temporarily decrease placental blood flow Ø Cannot be done if stimulated uterine contractions are contraindicated Ø Nipple stimulation or low-dose oxytocin Copyright © 2018 Elsevier Inc. All rights reserved. 20  Biophysical Profile ˜ BPP provides information on five parameters. Ø NST Ø Fetal breathing movements Ø Gross fetal movements Ø Fetal tone Ø Amniotic fluid volume ˜ The amniotic fluid index (AFI) is a method to quantify the amount of amniotic fluid visualized by ultrasound. Copyright © 2018 Elsevier Inc. All rights reserved. 21 Effects of Hypoxemia and Fetal Acidosis Copyright © 2018 Elsevier Inc. All rights reserved. 22  Maternal Assessment of Fetal Movement ˜ Movements by the fetus are assessed by the mother. ˜ They are often called “kick counts.” ˜ Several methods for the mother to count Ø At least 10 fetal movements within 1 to 2 hours Ø 5–10 movements per hour Copyright © 2018 Elsevier Inc. All rights reserved. 23  Question ˜ BPP includes information regarding all factors except __________. A. fetal breathing movements B. gross fetal movements C. amniotic fluid levels D. fetal length and gestational age Copyright © 2018 Elsevier Inc. All rights reserved. 24