Week 2 - Prenatal Testing

Question 1

Diagnostic Testing vs. Screening

Answer 1

Screening:
- Used to identify individual patients at risk
- Done for every patient in a category

Diagnostic:
- Used to confirm diagnosis
- Usually follow up after a screening
- Fetal diagnostic testing requires consent!

Question 2

What is required for fetal testing?

Answer 2

Informed Consent
- Nurses must respect parent’s decision

Question 3

Screening: Alpha-fetoprotein

What is it
Low levels indicate?
High levels indicate?

Answer 3

Alpha-fetoprotein - fetal protein that crosses the placenta into maternal circulation and can be measured in maternal blood (MSFAP)

Low levels: Trisomy, monosomy (chromosomal abnormalities)
High levels: Anencephaly, spina bifida, gastroschisis (Open NTDs and Body Wall defects)

When: Initial screening at 16 & 18 weeks of gestation

• False positives are common
• Normal levels of AFP aren’t a guarantee - additional screening recommended for high-risk groups

Question 4

Screening: Multiple-Marker

Quad Screen
When is it taken?

Answer 4

Quad-Screen:
- AFP (alpha-fetoprotein).
- HCG (human chorionic gonadotropin).
- Estriol (a form of estrogen).
- Inhibin-A
Taken from 15-22 weeks gestation

Question 5

Diagnostic/Screening: Ultrasound:

What is it

Answer 5

High-frequency sound waves are aimed at body tissues
- directed through tissues of the abdomen or vagina to provide two-dimensional images

Question 6

Ultrasound: First Trimester

Purpose
Procedure

Answer 6

Purpose:
- Confirm pregnancy
- Verify location of the baby
- Detect multifetal gestations
- Determine gestational age
- Identify markers for screening

Procedure:
- Transvaginal

Question 7

Ultrasound: Second and Third Trimester

Purpose

Answer 7

• Confirm viability/wellbeing
• Evaluate baby’s anatomy
• Determine gestational age
• Assess serial fetal growth
• Compare growth of fetuses in multifetal gestations

Question 8

Benefits of ultrasound

Answer 8

2D, 3D, 4D and Doppler
- Clear visibility of fetus and surrounding structures
- Noninvasive
- Results obtained immediately
- Proven safe
- Widely available and portable

Question 9

Nonstress Test

Purpose
Procedure

Answer 9

Purpose:
- Evaluate fetal well being

Procedure:
- Done after 24 weeks (or at age of viability)
- Before procedure woman should void & baseline vitals should be taken
- Semi-Fowler’s
- Electronic fetal monitor (EFM) applies to abdomen
- Ultrasound transducer records fetal heart rate (FHR)

Question 10

Hydramnios / Polyhydramnios

What is it

Answer 10

Excessive amniotic fluid

Question 11

Oligohydramnios

What is it

Answer 11

Insufficient amniotic fluid

Question 12

Non Stress Test

Criteria
Results

Answer 12

Criteria:
Baseline HR: 110 - 160 bpm
Variability: Moderate = 5 - 15bpm
Accelerations:
<32 weeks: 10 bpm for 10 seconds
>32 weeks: 15 bpm for 15 seconds
Decelerations: None

Results:
- Reactive: Reassuring tracing meets all requirements
OR
- Nonreactive: Tracing does not demonstrate the required characteristics of a reactive tracing within a 40-minute period. Not necessarily ominous but may indicated need for more testing

Question 13

Nonstress Test:

Advantages vs. Disadvantages

Answer 13

Advantages:
- Noninvasive for patients and fetus
- Believed to be without risk
- Easily administered
- Results available immediately

Disadvantages:
- High false-positive rates, require additional testing
- Can be difficult with preterm fetus, multiple fetal pregnancy or uncooperative patient

Clarify results = vibroacoustic stimulation
- Uses sound stimulation to get fetal movement
- Confirm nonreactive NST

Question 14

Contraction Stress Test:

What is it?
Results?

Answer 14

Nipple stimulation or infusion of oxytocin is used to induce contractions. ​
​

Results​:
Negative (normal) – no decelerations are present​
Positive (abnormal) – decelerations are present

“normally, early decels are good because those are taken during labor when the baby’s head is being compressed. The CST is taken before labor, so decels should NOT be present here”

Question 15

Diagnostic-Biophysical Profile:

What is it?

Answer 15

Scale 0-10:
- FHR
- Fetal Tone
- Amniotic fluid volume
- Breathing movements
- Gross body movement

Score:
8-10 = normal
4-6 = concerned for fetal asphyxia
<4 = likely chronic fetal asphyxia

Question 16

Diagnostic-Amniocentesis:

Differentiate purpose in 2nd/3rd trimester
Purpose in both 2nd & 3rd trimester

Answer 16

Second trimester purpose:
- Collect fetal cells to identify chromosome abnormalities

Third trimester purpose:
- Test to determine fetal lung maturity
- Lecithin/sphingomyelin (L/S)

2nd + 3rd Trimester purpose:
- Diagnose intrauterine infections
- Tests for fetal hemolytic disease
- Determine fetal bilirubin concentration (Rh sensitized)

Question 17

Amniocentesis:

Procedure
Benefits
Risks

Answer 17

Procedure:
- Can be done from 14 weeks until delivery
- Ultrasonography used to identify largest pockets of amniotic fluid that can safely be sampled
- Spinal needle inserted into pocket of fluid; 1-2mL fluid discarded
- Approximately 20mL of fluid removed for analysis

Benefits:
- Simple; statistically safe
- Relatively painless procedure
- Takes a short time
- Familiar to most obstetricians

Risks:
- Death of child rate <1%
- Higher risk with early use
- Transfer of fetal blood to maternal circulation

Question 18

When can amniocentesis be done?

Answer 18

14 Weeks of gestation until delivery

Question 19

Percutaneous Umbilical Blood Sampling (PUBS):

Purpose
Procedure
Risks

Answer 19

Purpose:
- Aspirate fetal blood from umbilical cord for prenatal diagnosis
- Or access for intrauterine transfusion

Procedure:
- High resolution ultrasound is used to locate the fetus, placenta and umbilical cord and guide needle insertion
- Needle is inserted into the umbilical cord near the site at which the cord meets the placenta

Risks:
- Occasional variety of life-threatening complications for the fetus

Question 20

Chorionic Villus Sampling (CVS):

Purpose
Procedure
Advantages
Risks

Answer 20

Purpose:
Diagnose fetal chromosomal, metabolic or DNA abnormalities

Procedure:
- Usually performed between 10 and 13 weeks of gestation
- Transcervical or Transabdominal

Advantages:
- Earlier results than amniocentesis

Risks:
- Rate of child death after CVS similar to amniocentesis
- Reports of limb reduction defects

Question 21

WHEN is a Non Stress Test taken?

Answer 21

Done after 24 weeks

Question 22

When can amniocentesis be done?

Answer 22

Anywhere from 14 weeks until delivery