Ch. 9 Knowledge Check Questions

4. Why is ultrasound transmission gel used during obstetric ultrasounds?

A water-soluble transmission gel or lotion is used to increase transmission of sound waves.

19. Why is amniotic fluid volume an important parameter in BPPs and MBPPs?

Amniotic fluid volume is an important parameter in bio- 6. physical profiles (BPPs) and modified biophysical profiles (MBPPs) because it is the only long-term indicator of fetal oxygenation.

3. What information is obtained with a basic ultrasound?

Basic obstetric ultrasound provides the following information: . Maternal anatomy (cervix, uterus, adnexa) . Number of fetuses . Biometry (fetal measurements of specific structures) that estimates gestational age and fetal weight or determines whether a structure is a normal or abnormal size . Survey of fetal anatomy . Fetal presentation . Presence of fetal cardiac activity . Placental location . Amniotic fluid volume

6. What conditions are associated with elevated AFP levels?

Neural tube defects (NTDs) are most commonly associated with elevated alpha-fetoprotein (AFP) levels. Other conditions include underestimation of gestational age, undiagnosed multiple gestation, fetal demise, conditions associated with fetal edema such as cystic hygroma, and abdominal wall defects such as gastroschisis.

5. What is an NT measurement? What aneuploidy is associated with an increased NT measurement?

Nuchal translucency (NT) is a first-trimester ultrasound measurement of the fluid-filled space measured at the back of the fetal neck. An enlarged NT, often defined as 3.0 mm or greater or above the 99th percentile for gestational age, is associated with trisomy 21 as well as structural abnormalities such as congenital heart defects.

15. What criteria are used to determine whether an NST is reactive or nonreactive?

Reactive NSTs contain two or more FHR accelerations within a 20-minute period. Accelerations are defined as visually apparent increases in the FHR that reach a peak of 15 beats per minute (bpm) above the baseline, with the entire acceleration lasting a minimum of 15 seconds but less than 2 minutes ("15 x 15"). Before 32 weeks of gestation, accelerations are defined as visually apparent increases in the FHR that reach a peak of 10 bpm above the baseline with the entire acceleration lasting at least 10 seconds ("10 X

11. What risks are associated with early amniocentesis?

Risks of early amniocentesis (before 15 weeks of gestation) include increased degree of difliculty of the procedure with an increased failure rate, inadequate amniotic fluid volume for sampling, increased rates of pregnancy loss, and amniotic fluid leakage that has been linked to talipes equinovarus (clubfoot) deformity in the infant.

10. What are second— and third—trimester indications for amniocentesis?

Second trimester indications for amniocentesis include prenatal diagnosis of chromosomal, genetic, and metabolic disorders. Third-trimester indications are to test for fetal lung maturity (FLM), identification of fetal infection, and therapeutic amniocentesis for amniotic fluid volume disorders such as hydramnios and oligohydramnios.

20. Describe the process of shunting in relationship to fetal oxygenauon.

Shunting occurs because the fetus redirects blood from areas not critical to fetal life, such as the kidneys, gastrointestinal tract, and extremities, to the vital organs, which include the heart, brain, and adrenal gland. If changes in oxygenation are prolonged, blood flow to the fetal kidneys ceases. Therefore oligohydramnios in fetuses with normal renal structures and intact amniotic membranes suggests prolonged fetal hypoxia and is a strong indication of fetal compromise.

12. Why is surfactant important for fetal lung maturity?

Surfactant is important for fetal lung maturity because it reduces surface tension on the inner walls of the alveoli, allowing them to stay slightly open during exhalation. Additionally, surfactant stabilizes lung volume, alters lung mechanics, and maintains gas exchange in the lung. Without adequate surfactant, lung walls adhere to one another, making alveoli inflation during inhalation diflicult, which in turn increases the amount of pres- 20. sure required to keep alveoli open. If this situation is not corrected, impaired oxygenation eventually leads to respiratory distress syndrome (RDS) and other neonatal complications, increasing the rates of neonatal morbidity and mortality.

18. What are the four biophysical characteristics evaluated with ultrasound during a BPP and what do they reflect?

The four biophysical characteristics evaluated with ultrasound during a biophysical profile (BPP) are fetal movement, fetal tone, fetal breathing movement, and amniotic fluid amount. Biophysical characteristics are a reflection ofthe central nervous system (CNS) and provide an indirect means of evaluating fetal oxygenation.

17. Identify the four results of CST interpretation and explain each one.

The interpretation criteria for CST are as follows: Negative—No late decelerations Positive—Late decelerations are present with a min- 4. imum of 50% of the contractions even when fewer than three contractions occur in 10 minutes Equivocal—suspicious—Intermittent late decelerations or significant variable decelerations (sudden decreases in the FHR that quickly return to the baseline) Equivocal—FHR decelerations in the presence of con- 5. tractions that are more frequent than every 2 minutes or last longer than 90 seconds Unsatisfactory—Fewer than three contractions in 10 minutes or a tracing that cannot be interpreted

8. What is the major advantage of CVS compared with amniocentesis?

The major advantage of chorionic villi sampling (CVS) compared with amniocentesis is that it is done in the first trimester (10 to 13 weeks gestation) and provides faster results. This prevents a long delay between screening and diagnosis and provides results before the mother perceives fetal movement. This may ease the decision-making process regarding continuation of the pregnancy and decrease emotional distress on the patient and family.

13. What is the primary goal of antepartal fetal testing?

The primary goal ofantepartum fetal testing is identification of fetuses at risk for permanent neurologic injury or stillbirth so timely intervention can be done to decrease perinatal morbidity and mortality rates.

16. Why are contractions necessary for CST interpretation?

Contraction stress tests (CSTs) determine fetal well-being by monitoring FHR responses to contractions. Healthy, well oxygenated fetuses can physiologically tolerate the interrupted placental blood flow which occurs during contractions and maintain FHR with normal characteristics such as a stable baseline rate and accelerations. In compromised fetuses, brief interruptions of oxygen transfer during contractions can result in late decelerations.

1.What is the primary objective of prenatal screening and diagnosis?

The primary objective of prenatal screening and diagnosis is to detect disorders or abnormalities that could affect the woman, fetus, and newborn.

2. What are three categories of obstetric ultrasound? What are the two routes used for obstetric ultrasound?

The three categories of obstetric ultrasound are standard (or basic), limited, and specialized (detailed or targeted). The two routes used for obstetric ultrasound are transvaginal and transabdominal.

9. What risk is associated with CVS when the procedure is performed at less than 10 weeks?

There is an increased risk oflimb reduction defects associated with chorionic villi sampling (CVS) when the procedure is performed before 10 weeks gestati

14. Describe one method of fetal movement counting

To explain fetal movement counting to a patient, the nurse should tell her to rest in a quiet location and count distinct Shunting occurs because the fetus redirects blood from areas not critical to fetal life, such as the kidneys, gastrointestinal tract, and extremities, to the vital organs, which include the heart, brain, and adrenal gland. If changes in oxygenation are prolonged, blood flow to the fetal kidneys ceases. Therefore oligohydramnios in fetuses with normal renal structures and intact amniotic membranes suggests prolonged fetal hypoxia and is a strong indication of fetal compromise. CHAPTER 10 fetal movements, such as kicks or rolls. Once 10 move- 1. ments are perceived, record the number of movements and amount of time on a cell phone app or piece of paper. If you do not feel 10 movements in 1 to 2 hours, or you notice a decrease in the movements, notify your provider.

7. What is multiple—marker screening? Why is it performed?

Multiple-marker screening, sometimes called a triple or quad screen, is a maternal blood test for three or four substances (human chorionic gonadatropin [hCG], alpha-fetoprotein [AFP], unconjugated estriol [uE3], and, in the quad screen, inhibin A). It is performed to evaluate a woman's risk for trisomy 21, trisomy 18, and open neural tube defects (NTDs).