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

Psychologic Reactions to Antenatal Testing

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

  • Patients retain the right to refuse testing if desired.

  • Ultrasound (US) has become an almost routine procedure; it is important to provide counseling to patients regarding their feelings of shock and confusion post-testing.

Methods of Ultrasound Scanning

Transabdominal Ultrasound

  • Full bladder is necessary for optimal assessment of structures.

  • Generally considered a painless procedure lasting 20 to 30 minutes.

  • ### Transvaginal Ultrasound

    • Requires an empty bladder.

    • Capable of identifying cervical length and funneling.

    • The lithotomy position provides clearer images.

    • Utilized earlier in pregnancy compared to transabdominal ultrasound, especially in the second to third trimester.

Purpose and Outcomes of Ultrasound

First Trimester

  • Confirm the location of pregnancy.

  • Identify fetal heart rate and fetal breathing movements.

  • Approximate gestational age.

  • Rule out nonviable pregnancies.

  • ### Second and Third Trimester

    • **Fetal Anatomy Scan:

    • Screens for genetic disorders.

    • Diagnoses fetal or congenital malformations.

    • Evaluates fetal growth.

    • Identifies fetal sex. **

    • **Amniotic Fluid Index (AFI):

    • Evaluates fetal well-being.

    • Assess fetal presentation.

    • Establish placental location and quantify amniotic fluid levels.**

First Trimester Combined Screening (1 of 2)

  • ### Nuchal Translucency Testing (NTT)

    • Ultrasound assesses fluid accumulation between the posterior cervical spine and the overlying skin in the fetal neck (nuchal fold).

    • Conducted between 11 weeks and 0 days to 13 weeks and 6 days

    • Performed in conjunction with maternal serum blood tests measuring plasmaprotein A (PAPP-A) and free beta hCG.

    • Important to note that this does not provide a definitive diagnosis—additional testing like amniocentesis is required for confirmation.

First Trimester Combined Screening (2 of 2)

  • ### Cell-Free Fetal DNA (cffDNA) Testing

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

    • Rh-negative mothers require RhoGAM treatment; if the cffDNA indicates possible Down syndrome, further testing is recommended.

Second Trimester Assessments

  • ### Quad Screening

    • Most commonly used test screening for Down syndrome, trisomies 13 and 18, and neural tube defects (NTDs).

    • Serum assessment includes:

    • Alpha-fetoprotein (AFP)

    • Human chorionic gonadotropin (hCG)

    • Unconjugated estriol (UE3)

    • Dimeric inhibin-A

    • Noninvasive test; provides no definitive diagnosis, typically performed between 16 to 18 weeks gestation.

Third Trimester Fetal Surveillance

Fetal Movement Assessment (Fetal Kick Counts)

  • Initiated at 28 weeks; count fetal movements at the same time each day.

  • Expect at least 10 movements in a span of 2-3 hours.

  • Noninvasive and cost-effective method serving as an indirect measure of fetal central nervous system well-being.

  • Vigorous fetal movements generally indicate wellness, while a lack of movement raises concerns of potential issues such as chronic placental inefficiency.

  • ### Nonstress Test (NST)

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

    • An adequately oxygenated fetus should demonstrate an accelerated fetal heart rate (FHR) in response to movement.

    • There are chances of false positives; careful interpretation of baseline data is crucial.

Reactive Nonstress Test (NST)

  • Defined by:

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

    • The strip displays FHR at the top and uterine activity tracing at the bottom, recognizing at least 15 beats above the baseline for 15 seconds during each movement.

Advantages of NST

  • Quick to execute; simple interpretations.

  • Inexpensive; can be done in a clinic or office setting.

  • No known adverse effects on the mother or baby.

Disadvantages of NST

  • Obtaining a suitable tracing can be challenging.

  • Patient must remain still for approximately 20 minutes.

  • There is a significant false-positive rate.

NST Results Interpretation

  • Desirable Response (Reactive NST):

    • For gestational age > 32 weeks: Two or more accelerations of FHR of 15 beats/min lasting at least 15 seconds over a 20-minute period.

    • For preterm fetuses (< 32 weeks): Increase of 10 beats above baseline for 10 seconds within a 20-minute window.

  • Nonreactive NST Result:

    • Characterized by an absence of FHR accelerations in conjunction with fetal movement. Concern arises when the baseline FHR remains low, indicating potential issues.

Contraction Stress Test (CST)

  • Evaluates placental respiratory functions (gas exchange) and identifies potential fetal risk for asphyxia.

  • Monitors fetal heart rate responses during contractions.

Disadvantages of CST

  • Tests are time-consuming and can yield high false positive rates.

CST Contraindications

  • Third-trimester bleeding from placenta previa.

  • Unexplained vaginal bleeding or marginal abruptio placentae.

  • Previous cesarean with vertical incision (classical cesarean).

  • Premature rupture of membranes or cervical insufficiency.

Performing the CST

  • Requires contractions either spontaneous or induced (e.g., through intravenous oxytocin or breast stimulation).

  • Continuous electronic fetal monitoring gathers ongoing data during the test.

  • Aim is to observe three contractions over a 10-minute window.

CST Results Interpretation

  • Desired Results:

    • Negative CST with reactive NST showing three timely, adequate contractions with no late decelerations.

  • Positive CST: Repetitive late decelerations found with over 50% of contractions.

  • Equivocal or Suspicious Results: Nonpersistent late decelerations or those correlated with tachysystole, indicating that the baby might not tolerate labor.

Amniotic Fluid Index (AFI)

  • Oligohydramnios can indicate reduced uteroplacental perfusion.

  • Amniotic fluid volume is influenced by fetal urine output and swallowing. An AFI score of 5 or less necessitates further evaluation, as it's linked to poor outcomes.

Biophysical Profile (BPP)

  • Consists of 5 fetal biophysical variables:

    1. Fetal heart rate acceleration (from NST).

    2. Fetal breathing (from ultrasound).

    3. Fetal movements (from ultrasound).

    4. Fetal tone (from ultrasound).

    5. Amniotic fluid volume (from ultrasound).

BPP Scoring Criteria

  • Scores are assigned as follows:

    • 2 points for each normal finding.

    • 0 points for each abnormal finding.

    • Total possible score is 10:

    • 8-10 indicates low risk.

    • 6 indicates abnormal results suggesting possible acidemia due to inadequate blood flow.

  • 4 or below indicates significant oxygenation issues.

Indications for BPP

  • Noteworthy clinical scenarios include:

    • Decrease in fetal movement.

    • Nonreactive NST.

    • Management for Intrauterine Growth Restriction (IUGR).

    • Preterm labor, gestational diabetes, hypertensive disorders, postterm pregnancies, and premature rupture of membranes (PROM).

Doppler Flow Studies

  • Employed in high-risk pregnancies to assess placental function and velocity of blood flow within vessels.

  • Noninvasive and assesses both maternal and fetal circulation through measuring blood flow velocity expressed as the Systolic/Diastolic (S/D) ratio.

Placental Maturity

  • Graded via ultrasound assessing basal layer, chorionic plate, and placental substance, yielding grades from 0-3 (3 indicating mature status).

  • Factors impacting placental maturity include:

    • Maternal smoking.

    • Postterm pregnancy.

    • Preeclampsia.

    • Gestational diabetes manifestations.

Amniocentesis

  • A procedure to detect genetic and metabolic abnormalities, determine fetal lung maturity in the third trimester, and identify neural tube defects.

  • Ideally performed between 15-16 weeks, though applicable anytime thereafter. Diagnostic tests include the L/S (Lecithin/Sphingomyelin) ratio to assess fetal lung maturity.

Indications for Amniocentesis

  • Recommended for pregnant women aged 35 or more at their due date.

  • Couples with a history of children with birth defects or prior abnormal screening results.

Amniocentesis Procedure

  • The patient is prepared with ultrasound to locate the placental site and amniotic fluid pockets.

  • As the needle enters, resistance is felt upon penetrating the skin, fascia, and uterine wall before entering the amniotic cavity for fluid aspiration. If the mother is Rh-negative, RhoGAM is administered post-test to mitigate potential complications.

Risks and Side Effects of Amniocentesis

  • Common occurrences include transient vaginal spotting and cramping, along with possible amniotic fluid leakage and infection.

  • Early amniocentesis may result in higher rates of fetal loss.

  • Nursing duties include assisting during the procedure, patient support pre- and post-procedure, and assessing maternal blood type as a consideration for RhoGAM.

Chorionic Villus Sampling (CVS)

  • A procedure performed early in pregnancy (between 10 to 12 weeks) to detect same genetic, metabolic, and DNA abnormalities as amniocentesis but with no detection capability for neural tube defects.

CVS Risks

  • Potentials for spontaneous abortion, fetal limb reduction defects, and other complications such as rupture of membranes and vaginal spotting.

CVS Benefits

  • Offers earlier diagnosis compared to amniocentesis and allows for early sex determination while also assessing various genetic conditions such as Down syndrome and muscular dystrophies.