Assessment of Fetal Well-Being

Olds’ Maternal-Newborn Nursing & Women’s Health: Assessment of Fetal Well-Being - Chapter 15

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Psychologic Reactions to Antenatal Testing

  • The need for testing often provokes feelings of fear and anxiety in patients.

  • Patients hold the option to refuse testing.

  • Ultrasound (US) is nearly routine; it is essential to provide counseling to address feelings of shock and confusion related to testing results.

Methods of Ultrasound Scanning

Transabdominal Ultrasound

  • Requires a full bladder for optimal assessment of fetal structures.

  • It is a painless procedure that typically lasts 20–30 minutes.

Transvaginal Ultrasound

  • Requires an empty bladder and can identify specific parameters such as:

    • Cervical length.

    • Funnel shapes.

  • Patient positioning is typically lithotomy for clearer images.

  • This method is preferred earlier in the pregnancy (2nd to 3rd trimester) for better image quality.

Ultrasound in First Trimester

  • Objectives include:

    • Confirming the location of the pregnancy.

    • Identifying fetal heart rate and fetal breathing movements.

    • Approximate gestational age determination.

    • Rules out a nonviable pregnancy (using measurements to estimate age).

    • Locates the placenta position and fetal orientation.

Ultrasound in Second & Third Trimester

  • Conducted to assess:

    • Fetal anatomy scan to screen for genetic disorders.

    • Diagnose fetal or congenital malformations.

    • Evaluate fetal growth.

    • Identify the sex of the fetus.

    • Assess Amniotic Fluid Index (AFI) for overall well-being of the fetus.

    • Fetal presentation and placental location.

First Trimester Combined Screening (1 of 2)

Nuchal Translucency Testing (NTT)

  • Performed between 11 weeks 0 days and 13 weeks 6 days.

  • Uses ultrasound to assess fluid accumulation in the nuchal fold behind the fetal neck.

  • Done in conjunction with maternal serum blood tests measuring:

    • Plasma-protein A analyte levels (PAPP-A).

    • Free beta hCG.

  • Important to note that this is a screening tool only, not a definitive diagnosis (diagnosis possible via amniocentesis).

First Trimester Combined Screening (2 of 2)

Cell-free Fetal DNA (cffDNA) Testing

  • Conducted through a maternal blood test.

  • Exhibits a 98% detection rate for fetal trisomy 21 (Down syndrome) and lower rates for trisomies 13 and 18.

  • Rh-negative mothers are advised to receive RhoGAM.

  • If positive for abnormalities, additional testing is recommended.

Second Trimester Assessments

Quad Screening

  • The most widely used screening test for:

    • Down syndrome (trisomy 21).

    • Trisomies 13 and 18.

    • Neural tube defects (NTDs).

  • Serum assessment includes:

    • Alpha-fetoprotein (AFP).

    • Human chorionic gonadotropin (hCG).

    • Unconjugated estriol (UE3).

    • Dimeric inhibin-A.

  • This is a noninvasive procedure, typically conducted during the 2nd trimester (optimal at 16-18 weeks).

Third Trimester Fetal Surveillance

Fetal Movement Assessment (Fetal Kick Counts)

  • Initiation at 28 weeks gestation; count movements at the same time each day.

  • Expect to feel 10 movements within 2-3 hours.

  • This is a noninvasive and cost-effective method that serves as an indirect measure of fetal CNS health.

  • Vigorous movements generally indicate fetal well-being; lack of movement or significant decreases could signify issues like chronic placental inefficiency, hypertension, diabetes, or renal disease.

Reporting Guidelines

  • Report to the healthcare provider if:

    • There are fewer than 10 movements in a 3-hour period.

    • There’s a significant reduction in fetal movement compared to baseline.

    • There is a perception of decreased fetal movement over a 24-hour period.

Nonstress Test (NST)

Purpose

  • A widely used method for evaluating fetal status alone or as part of a biophysical profile (BPP).

  • An adequately oxygenated fetus with an intact CNS should show an accelerated fetal heart rate (FHR) in response to movements.

  • False-positive results can occur; monitoring the baseline helps interpret results effectively.

Reactive NST

  • Defined by:

    • Accelerations of at least 15 beats/min lasting 15 seconds with each movement.

    • The assessment strip displays FHR (top) and uterine activity (bottom).

Advantages of NST

  • Quick and easy to perform.

  • Provides straightforward interpretation.

  • Inexpensive and can be conducted in various settings.

  • No known side effects.

Disadvantages of NST

  • May be challenging to obtain suitable tracings.

  • Requires the woman to remain still for approximately 20 minutes.

  • High false-positive rate can lead to unnecessary worry.

NST Results Interpretation

Reactive Results (Desired)

  • For pregnancies over 32 weeks:

    • At least two accelerations of FHR (15 beats/min lasting 15 seconds) in 20 minutes.

  • For preterm fetuses (under 32 weeks):

    • FHR should elevate 10 beats above baseline for 10 seconds in a 20-minute window.

Nonreactive NST

  • Occurs when there are no accelerations of FHR with fetal movement; baseline may remain stable around 130 beats/min.

  • Cannot rule out potential issues but indicates a need for further assessment/comparison.

Contraction Stress Test (CST)

Purpose

  • Evaluates placental respiratory function (oxygen and carbon dioxide exchange).

  • Identifies fetuses at risk for intrauterine asphyxia.

  • Observes the FHR response to uterine contractions.

Disadvantages of CST

  • Time-consuming with the potential for high false-positive results.

CST Contraindications

  • Instances that inhibit safe testing include:

    • Third-trimester bleeding from placenta previa.

    • Previous cesarean with classical incision.

    • Cervical insufficiency, premature rupture of membranes, or abnormal maternal reproductive organs.

Performing the CST

  • Requires contractions; spontaneous contractions are rare before labor onset.

  • Contractions may be induced using:

    • Intravenous oxytocin (Pitocin).

    • Breast stimulation.

  • Continuous monitoring of fetal heart rate and uterine contractions is critical, aiming for at least three contractions within 10 minutes.

CST Results

  • A Negative CST with a reactive NST is desired:

    • Good-quality contractions lasting over 40 seconds in 10 minutes.

    • No evidence of late decelerations.

  • A Positive CST indicates repetitive late decelerations with greater than 50% of contractions.

  • An Equivocal or Suspicious Result shows nonpersistent late decelerations or decelerations linked to tachysystole.

Amniotic Fluid Index (AFI)

  • Decreased uteroplacental perfusion leads to oligohydramnios.

  • AFI is determined by:

    • Fetal urine output.

    • Fetal swallowing.

  • An AFI of 5 cm or less requires further evaluation.

Biophysical Profile (BPP)

  • An assessment of five fetal biophysical variables:

    1. Fetal heart rate acceleration (NST).

    2. Fetal breathing (ultrasound).

    3. Fetal movements (ultrasound).

    4. Fetal tone (ultrasound).

    5. Amniotic fluid volume (ultrasound).

BPP Scoring Criteria

  • Each normal finding scores 2 points, while each abnormal finding scores 0 points.

  • Maximum score is 10 points.

    • Score 8-10 indicates low risk.

    • Score 6 indicates abnormal findings, possibly acidemia (inadequate oxygenation).

    • Score of 4 or less indicates serious issues needing attention.

Indications for BPP

  • It is indicated in:

    • Decreased fetal movement.

    • Nonreactive NST.

    • Management of intrauterine growth restriction (IUGR).

    • Preterm labor.

    • Gestational diabetes and hypertensive disorders.

    • Postterm pregnancies or premature rupture of membranes (PROM).

Doppler Flow Studies

  • Used in high-risk pregnancies for assessing:

    • Placental functioning and velocity of blood flow in blood vessels.

  • Noninvasive techniques that focus on both maternal and fetal circulation.

  • Specifically measures:

    • Systolic/diastolic (S/D) ratio.

  • Reduced umbilical artery flow can signal complications.

Placental Maturity

Grading Process

  • Evaluated using ultrasound to observe changes in:

    • Basal layer.

    • Chorionic plate.

    • Placental substance.

  • Graded from 0 to 3, with 3 indicating maturity with extensive calcifications.

  • Inadequate placental function is a concern for further assessment.

Factors Influencing Placental Maturity

  • Factors that can cause premature placental maturity include:

    • Maternal smoking.

    • Postterm pregnancy.

    • Preeclampsia.

    • Gestational diabetes.

Amniocentesis

  • Utilized for detecting:

    • Genetic, metabolic, and DNA abnormalities.

    • Determining fetal lung maturity in the third trimester.

    • Detecting neural tube defects.

  • Ideally performed between 15-16 weeks, though valid at any point.

    • Can measure the Lecithin/Sphingomyelin (L/S) ratio for lung maturity evaluation.

    • Also measures alpha-fetoprotein levels.

Indications for Amniocentesis

  • Recommended for:

    • Pregnant women aged 35 or older at their due date.

    • Couples with a history of genetic disorders.

    • Pregnant women with abnormal screening results.

Procedure

  • Involves ultrasound guidance to locate a fluid pocket for needle insertion.

  • Upon entering the amniotic cavity, fluid is withdrawn.

  • If the mother is Rh-negative, RhoGAM is required and monitoring for potential complications is necessary.

Risks and Side Effects of Amniocentesis

  • Possible outcomes include:

    • Transient vaginal spotting or cramping.

    • Amniotic fluid leakage.

    • Chorioamnionitis.

    • Increased rate of loss if performed too early.

  • Nursing management includes assisting during the procedure and providing patient support, along with determining maternal blood type and RhoGAM needs.

Chorionic Villus Sampling (CVS)

  • This procedure is performed for early diagnosis (10-12 weeks) of:

    • Genetic, metabolic, and DNA abnormalities.

  • Cannot detect neural tube defects; used primarily for genetic evaluations.

Risks Associated with CVS

  • Possible complications include:

    • Spontaneous abortion.

    • Fetal limb reduction defects.

    • Failure to obtain adequate tissue.

    • Ruptured membranes or leakage of amniotic fluid.

    • Chorioamnionitis and intrauterine infections.

Benefits of CVS

  • Provides earlier diagnosis as compared to amniocentesis.

  • Can detect:

    • Fetal karyotype and hemoglobinopathies.

    • Down syndrome and Duchenne's muscular dystrophy.

    • Early sex determination (24 hours to 1 week post-procedure).