Chapter 10: Antepartum Fetal Assessment Flashcards
What factors increase the risk for the fetus during pregnancy (indicates a need for fetal diagnostic testing)?
- Medical Conditions: diabetes, HTN, seizure disorders, autoimmune diseases
- Demographic Factors: age (<16 or >35) and poverty
- Obstetric Factors: previous pre-term labor, stillborn or infant that has had congenital anomalies
- Pre-existing maternal factors: prepregnancy BMI that is over or underweight, use of drugs, etc.
What are indications for antepartum fetal diagnostic testing?
- To detect congenital anomalies
2. To evaluate the condition of the fetus
Ultrasounds in pregnancy can be used to
- Confirm pregnancy
- Verify location of pregnancy
- Identify multifetal gestations
- Determine gestational age
- Confirm viability of fetuses
- Evaluate fetal anatomy
- Assess fetal growth
- Identify the amount of fluid
- Identifying fetal anomalies
Abdominal Ultrasound
Most often used during the second and third trimesters, allowing clear views of the fetus and placenta.
Transvaginal Ultrasound
Allows clear visualization of the uterus, gestational sac, embryo and pelvic structures such as the ovaries and Fallopian tubes during the first trimester.
Ultrasound Risks
Thought to be very safe
Amniotic Fluid Index
An ultrasound examination in which the vertical depth of the largest fluid pocket in each of the four quadrants of the uterus is measured and totaled.
Normal AFI at 20 weeks
700-1000 mL
What AFI indicates (Poly)Hydramnios?
AFI higher than 18-20 cm
What AFI indicates Oligohydramnios?
AFI <5 cm
What are associated complications of (poly)hydramnios?
- Diabetes (fetal polyuria)
- CNS anomalies (irritates the CNS -> increase in fetal urination)
- GI anomalies
- Premature rupture
- Overdue pregnancy
What are associated complications of oligohydramnios?
- Poor placental blood flow
- Preterm membrane rupture
- Failure of the fetal kidney development
- Blocked urinary excretion
Alpha-fetoprotein Testing
- Tests the level of maternal serum alpha-fetoprotein (plasma protein produced by the fetus) because the level of alpha-fetoprotein is altered by fetal age and number of fetuses.
- Accurate gestational age is needed when testing.
When should alpha-fetoprotein testing be done?
Time sensitive -> must be done between 15-20 weeks
What is the purpose of alpha-fetoprotein testing?
Screens for anomalies such as trisomy 21, 18, 13 and NTD
What are the risks for alpha-fetoprotein testing?
- 1 in 20 are false positive
- Can be costly
- Small risk of miscarriage and premature rupture
Amniocentesis
- Transabdominal puncture of the amniotic sac to obtain a sample of amniotic fluid that contains fetal cells and biochemical substances for laboratory examination.
- Much more accurate measure for advanced maternal age moms.
When should amniocentesis be performed?
Best performed at 15-20 weeks of gestation because adequate fluid volume and the quantity of viable fetal cells provide the best sample for evaluation.
What is amniocentesis used for?
- The most common, to identify chromosomal abnormalities.
- Advance maternal age
- Gender determination
- Pregnancy after 3 or more spontaneous abortions
- Elevated levels of maternal serum alpha-fetoprotein or multiple-marker screen that remain unexplained
- Maternal Rh sensitization of maternal Rh-negative blood to fetal Rh-positive blood
What are the risks when undergoing amniocentesis?
-Pregnancy loss rate of less than 1%. (Loss rate of 2%-5% noted after early amniocentesis)
Non-stress Test
A method for evaluating fetal status during the antepartum period by observing the response of the fetal heart rate to fetal movement.
What is the purpose of the nonstress test?
- Identifies whether an increase in the FHR occurs when the fetus moves.
- This indicates adequate oxygenation, a healthy neural pathway from the fetal CNS to the fetal heart and the ability of the fetal heart to respond to stimuli.
When should a nonstress test be performed?
Can start at 28 weeks because the CNS is considered mature at this time.
Usually done between 30-32 weeks.
How is a nonstress test evaluated?
- External electronic monitoring equipment is attached to the woman’s abdomen to detect fetal heart rate and any contractions.
- An ultrasound transducer to record fetal heart activity is secured on the woman’s abdomen where the fetal heart is heard most clearly.
- Next, a tocotransducer, which detects uterine activity and fetal movement is secured to the abdomen.
- Fetal reactivity is categorized as reactive (reassuring) and non reactive (nonreassuring)
What are the risk factors of the nonstress test?
-false-positive test results can occur
-
What are nursing interventions from findings of the nonstress test?
Used to stimulate the fetus to elicit accelerations in the FHR through:
- Vibroacoustic stimulation
- Manipulation of the woman’s abdomen
- Having the mother drink orange juice to raise her glucose level
What is a biophysical profile (BPP)?
Methods for evaluating fetal status during antepartum period based on five variables originating with the fetus.
What are risk factors of a biophysical profile?
-
What is a fetal movement assessment?
Assessment of movements by the fetus, “kick counts”.
Fetal movement is associated with fetal condition and daily evaluation of these movement provides a way of evaluating the fetus.
Vibroacoustic Stimulation
Uses sound stimulation to elicit fetal movement.
May be able to confirm nonreactive NST findings.
Appears to be safe for fetus in terms of hearing at 33 weeks gestation or older.
Brain responses to auditory stimulation appear in the fetus between what weeks?
26 and 28 weeks of gestation.
What are the five variables used in a biophysical profile (BPP)?
- Fetal Heart Rate
- Breathing Movements
- Gross Body Movements
- Muscle Tone
- Amniotic Fluid Volume
BPP Scoring? (Not sure if need to know)
…
Reassuring Nonstress Test Results
Two accelerations in 20 minutes (15 beats x 15 seconds)
How long does a transvaginal ultrasound take?
10-15 minutes to complete
How long does it take to complete an abdominal ultrasound?
Takes 10-30 minutes to complete.
If a full bladder is necessary during an abdominal ultrasound, what intervention should be done?
Have the woman drink several glasses of clear fluid about 1 hour before the examination and not void until after the examination.
What should be done before the NST?
Void and her baseline vital signs should be taken.
The fetal CNS centers that control each individual parameter of the BPP react differently to
Hypoxemia.
Parameters that disappear in fetal hypoxemia
- Fetal HR
- Fetal Breathing
- Fetal Movement
- Fetal Tone
- Reduced amniotic fluid volume
Because of this, absence of fetal tone indicates advance asphyxia and acidosis.
Why does oligohydramnios suggest prolonged fetal hypoxia?
During long periods of hypoxemia, the fetus shunts blood away from areas not critical to life including kidneys and lungs in order to supply vital organs such as the heart, brain and placenta.
If hypoxia is prolonged, blood flow to the fetal kidneys and lungs, which produce much of the amniotic fluid, may cease -> leading to oligohydramnios.
Color Doppler Ultrasound
Allows estimation and direction of blood flow and vascular resistance in fetal structures
AFP assessment
Is performed on maternal serum or amniotic fluid with the primary goal of detecting open body wall defects such as NTD’s.
Chorionic Villus Sampling
Is performed at 10-12 weeks of gestation to provide parents with information about chromosomal and other congenital defects in the first trimester of pregnancy.
Percutaneous umbilical blood sampling involves
The aspiration f blood from umbilical vessels to detect blood disorders, acid-base balance or fetal disease.
The most common complication of percutaneous umbilical blood sampling is
Fetal bradycardia.
The healthy fetus younger than 32 eels of gestation may not
Have accelerations that meet criteria for a reactive NST in the older fetus.
Contraction stress tests evaluate what?
Response of the FHR to recurrent short interruptions in placental blood flow and oxygen supply that occur with uterine contractions.
A modified BPP consists of
A NST and amniotic fluid volume.
Maternal Assessment of fetal movement
Is a noninvasive method of evaluating the fetus.
Advantage is that it has no cost.
The poorly oxygenated fetus usually moves __________ than the well-oxygenated fetus.
Less
Low levels of MSAFP suggests
Chromosomal abnormalities such as trisomy 21
Elevated MSAFP levels are associated with
Open NTDs and body wall defects
Why is accurate maternal weight necessary for the blood sample during Alpha-fetoprotein Testing?
Accurate maternal weight at the time of the blood sample is necessary because heavier women have greater dilution of their serum compared with thin women.
Multiple Marker Screening
- Two other markers, human chorionic gonadotropin (hCG) and unconjugated estriol, have been added to routine MSAFP evaluation to screen for chromosomal abnormalities.
- Screening increases detection of trisomy 18 and 21.
CVS is NOT used to
Detect open body wall defects such as spina bifida which requires amniotic fluid sampling
What is the benefit of CVS?
- Occurs in weeks 10-12, so results are known sooner than amniocentesis.
- Rate of pregnancy loss is similar to that of amniocentesis
The lecithin/sphingomyelin (L/S) ratio
is a test for estimating fetal lung maturity.
Lecithin
is a phospholipid component of fetal lung fluid and surfactant
Sphingomyelin
is a general amniotic membrane lipid.
Lecithin and sphingomyelin are present in approximately equal amounts until about
30 weeks of gestation.
An L/S ratio of at least 2 : 1 generally indicates
- adequate surfactant and mature fetal lungs.
- However, an L/S ratio of 2 : 1 may not indicate lung maturity in some conditions such as maternal diabetes.
amniotic fluid is usually tested for the presence of ___________________ in addition to the L/S ratio.
phosphatidylglycerol (PG) and phosphatidylinositol (PI), two other components of surfactant
The presence of PG and PI phospholipids supports
the likelihood that the fetal lungs are mature.
Percutaneous Umbilical Blood Sampling (PUBS)
also called cordocentesis, involves the aspiration of fetal blood from the umbilical cord for prenatal diagnosis or therapy
Major indications for PUBS include diagnosis and management of Rh disease, diagnosis of abnormal blood clotting factors, and determination of the acid-base status of the fetus.
diagnosis and management of Rh disease, diagnosis of abnormal blood clotting factors, and determination of the acid-base status of the fetus.
What umbilical vessel is used most commonly in PUBS?
The umbilical vein is used more commonly than the umbilical arteries because it is larger and less likely to constrict during the procedure
Knowing which vessel (umbilical vein or artery) was sampled is important when testing fetal acid-base parameters because
Blood returning to the fetus through the umbilical vein contains freshly oxygenated blood and lower carbon dioxide content compared with blood leaving the fetus and going to the placenta through the umbilical arteries.
RhoGAM
Given to prevent sensitization by any Rh-positive fetal blood that may have entered her circulation.
Contraindications for CVS
Maternal infection is a risk with this procedure, and it is contraindicated if the client has an active infection in the cervix, vagina, or pelvic area.
How long does it take for the results from CVS to be obtained versus results from amniocentesis?
CVS: known in 24-48 hours
Amniocentesis: known in 2-4 weeks
What is the purpose of amniocentesis for a client hospitalized at 34 weeks of gestation with pregnancy-induced hypertension?
During the third trimester, amniocentesis is most often performed to determine fetal lung maturity.
magnesium sulfate
used to stop preterm labor.
Betamethasone
is given to pregnant women in preterm labor to improve fetal lung maturity.
Elevated AFP levels are seen in
multiple gestations
underestimation of fetal age
threatened abortion
open neural tube defects (e.g., anencephaly, spina bifida)
abdominal wall defects (e.g., omphalocele, gastroschisis)
fetal demise.
Decreased levels of AFP are seen in
Down syndrome and a molar pregnancy.
Gestational trophoblastic disease.
