Assessment of Fetal Well-Being
Olds’ Maternal-Newborn Nursing & Women’s Health: Assessment of Fetal Well-Being
Twelfth Edition Chapter 15
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Psychologic Reactions to Antenatal Testing
Need for testing provokes fear and anxiety.
Patient has the option to refuse testing.
Ultrasound (US) has become almost routine.
Importance of counseling for shock and confusion experienced after testing.
Methods of Ultrasound Scanning
Transabdominal Ultrasound
Requires a full bladder to provide better visibility of structures.
This is a painless procedure lasting approximately 20–30 minutes.
Transvaginal Ultrasound
Requires an empty bladder.
More effective in assessing cervical length and funneling.
Patient is positioned in lithotomy position for clearer images, mainly utilized during the 2nd to 3rd trimester for better visibility of the fetus.
Ultrasound Assessments
First Trimester
Confirms the location of pregnancy.
Identifies fetal heart rate and fetal breathing movements.
Approximates gestational age.
Rules out a nonviable pregnancy.
Example: Measurement of the gestational age helps determine the position of the baby and the placenta.
Second & Third Trimester
Conducts a fetal anatomy scan:
Screens for genetic disorders.
Diagnoses fetal or congenital malformations.
Evaluates fetal growth.
Identifies fetal sex.
Measures Amniotic Fluid Index (AFI):
Evaluates fetal well-being.
Assesses fetal presentation.
Establishes placental location.
First Trimester Combined Screening
Nuchal Translucency Testing (NTT)
Ultrasound assesses fluid accumulation between the posterior cervical spine and overlying skin (nuchal fold).
Screening occurs between 11 weeks 0 days and 13 weeks 6 days.
Conducted in conjunction with a maternal serum blood test measuring plasma-protein A analyte levels (PAPP-A) and free beta hCG.
Note: This does not confirm a diagnosis; it screens for Down syndrome.
A definitive diagnosis requires invasive tests, such as amniocentesis.
Cell-Free Fetal DNA (cffDNA)
Maternal blood test with a 98% detection rate for fetal trisomy 21 and lower detection rates for trisomies 13 and 18.
Rh-negative mothers require RhoGAM because of the high invasiveness.
A positive result for Down syndrome necessitates further testing.
Second Trimester Assessments
Quad Screening
Most widely used test for screening Down syndrome (trisomy 21), trisomies 13 and 18, and neural tube defects (NTDs).
Provides serum assessment measuring:
Alpha-fetoprotein (AFP)
Human chorionic gonadotropin (hCG)
Unconjugated estriol (UE3)
Dimeric inhibin-A
Noninvasive assessment; does not confirm diagnosis.
Optimal testing occurs in the 2nd trimester, particularly at 16–18 weeks.
Third Trimester Fetal Surveillance
Fetal Movement Assessment (Fetal Kick Counts)
Initiated at 28 weeks gestation.
Mothers count movements at the same time daily, expecting 10 movements within 2-3 hours.
This is a noninvasive and cost-effective assessment of fetal central nervous system (CNS) functioning.
Vigorous movements indicate fetal well-being.
Concern for conditions like chronic placental insufficiency can arise from minimal to no movement.
Prenatal complications: Hypertension, diabetes, and renal disease can also reduce fetal movement.
Signs to Report to Healthcare Provider
Less than 10 movements in a 3-hour period.
Significantly reduced fetal movement levels.
Perception of decreased fetal movement over a 24-hour period.
Nonstress Test (NST)
A widely utilized method to evaluate fetal status.
Can be used alone or as part of a biophysical profile (BPP).
An adequately oxygenated fetus with an intact CNS should show accelerated fetal heart rate (FHR) in response to movements.
Note: There exists a high false-positive rate for this test.
Reactive NST
Defined as accelerations of FHR by 15 beats/min, lasting 15 seconds with each fetal movement.
Top of the NST strip records FHR; the bottom measures uterine activity tracing.
Affects how oxygenation is assessed for the fetus.
Advantages of NST
Quick to perform.
Easy interpretation.
Inexpensive.
Can be done in an office or clinic setting.
No known side effects.
Disadvantages of NST
Obtaining a suitable tracing can be challenging.
The woman must remain relatively still for at least 20 minutes.
High false-positive rate.
NST Results Interpretation
Reactive NST (desired result):
For fetuses over 32 weeks: At least two accelerations of FHR by 15 beats/min lasting 15 seconds or more over a 20-minute interval.
For preterm fetuses (under 32 weeks): At least 10 beats above baseline for 10 seconds in a 20-minute window.
Nonreactive NST:
Absence of FHR accelerations in response to fetal movement.
Baseline FHR example: 130 beats/min indicated with no accelerations.
Contraction Stress Test (CST)
Evaluates placental respiratory function (oxygen and carbon dioxide exchange).
Identifies fetuses at risk for intrauterine asphyxia.
Observes FHR response to contractions.
Disadvantages of CST
Can be time-consuming.
Yields high false-positive or equivocal results.
Contraindications for CST
Third-trimester bleeding from placenta previa.
Marginal abruptio placentae or unexplained vaginal bleeding.
History of classical cesarean incision.
Premature rupture of membranes.
Cervical insufficiency (incompetent cervix).
Cerclage in place or anomalies of maternal reproductive organs.
History of preterm labor if performed before term.
Multiple gestation.
Performing the CST
Requires presence of contractions; spontaneous contractions are unusual before labor onset.
Induction of contractions might require intravenous oxytocin (Pitocin) or breast stimulation.
Continuous electronic fetal monitoring to provide data on FHR and uterine contractions.
The goal is to observe three contractions in a 10-minute window.
Results of the CST
Negative CST with reactive NST desired: Three good-quality contractions lasting 40 or more seconds without late decelerations.
Positive CST indicates repetitive, persistent late decelerations with more than 50% of contractions.
Equivocal/Suspicious: Nonpersistent late decelerations or associated with tachysystole; implies baby won't tolerate labor well.
Amniotic Fluid Index
Decreased uteroplacental perfusion may lead to oligohydramnios.
Amniotic fluid volume determined by:
Fetal urine output.
Fetal swallowing.
AFI ≤ 5 mandates further evaluation; volume less than 5 cm correlates with poor pregnancy outcomes.
Biophysical Profile (BPP)
Assessment includes five fetal biophysical variables:
Fetal heart rate acceleration (NST).
Fetal breathing (via ultrasound).
Fetal movements (via ultrasound).
Fetal tone (via ultrasound).
Amniotic fluid volume (via ultrasound).
BPP Scoring Criteria
Score of 2 assigned for each normal finding; 0 for abnormal findings.
Total score maximum is 10.
Interpretation of scores:
8-10: Low risk.
6: Abnormal, possible acidemia.
< 4: Indicates inadequate oxygenation.
Indications for BPP
Decreased fetal movement.
Nonreactive NST.
Management of Intrauterine Growth Restriction (IUGR).
Preterm Labor.
Gestational Diabetes Mellitus (DM).
Hypertensive disorders.
Postterm pregnancies.
Premature Rupture of Membranes (PROM).
Doppler Flow Studies
Conducted in high-risk pregnancies to assess placental function and blood flow velocity within vessels.
Noninvasive assessment for both maternal and fetal circulation.
Measures Blood flow velocity:
Systolic/diastolic (S/D) ratio with normal decreases near term.
Studies reduced blood flow through the umbilical artery indicate risks.
Indications for Doppler Flow Study
Diagnosed IUGR.
Suspected late-term small for gestational age (SGA) due to unknown cause or hypertensive disorders/Pre-eclampsia.
Placental Maturity
Grading process via ultrasound measures changes in:
Basal layer.
Chorionic plate.
Placental substance.
Grading scale: 0 to 3;
Grade 3 indicates mature placenta with extensive calcifications implying inadequate placental function.
Factors causing accelerated placental maturity:
Maternal smoking.
Postterm pregnancy.
Preeclampsia.
Gestational diabetes.
Amniocentesis
Utilized for detecting genetic, metabolic, and DNA abnormalities.
Determines fetal lung maturity in the third trimester.
Can identify neural tube defects and presence of infections.
Ideally performed between 15-16 weeks, but can be performed anytime.
Diagnosis noted during 10-18 weeks, with 16 weeks being optimal.
Measures Lecithin/Sphingomyelin Ratio (LS ratio) to assess fetal lung maturity and also tests for alpha-fetoprotein.
Indications for Amniocentesis
Pregnant women aged 35 or older on their due date.
Couples with history of birth defects.
Pregnant women with any abnormal screening or genetic test results.
Procedure for Amniocentesis
Initial ultrasound locates the placental site and pockets of fluid.
Needle insertion involves feeling three levels of resistance as it passes through skin and uterine walls until reaching the amniotic cavity to withdraw fluid.
If the mother is Rh-negative, she requires Rhogam injection to prevent complications.
Risks and Side Effects of Amniocentesis
Transient vaginal spotting and cramping.
Possible amniotic fluid leakage.
Risk of Chorioamnionitis.
Higher rate of loss if performed early.
Chorionic Villus Sampling (CVS)
Used to detect genetic, metabolic, and DNA abnormalities.
Involves needle aspiration of chorionic villi from the placenta for first trimester diagnosis (usually at 10-12 weeks).
Cannot detect neural tube defects; recommended to proceed with quad screening for that.
Risks of CVS
Potential for spontaneous abortion.
Risk of fetal limb reduction defects.
Difficulty obtaining tissue samples.
Possible complications include rupture of membranes, leakage of amniotic fluid, vaginal spotting or bleeding, Chorioamnionitis, and intrauterine infections.
Benefits of CVS
Provides earlier diagnosis than Amniocentesis.
Can detect a range of conditions such as:
Fetal karyotype.
Hemoglobinopathies.
Phenylketonuria (PKU).
Down syndrome.
Duchenne muscular dystrophy.
Factor IX deficiency.
Early sex determination (within 24 hours to 1 week).