Maternal-Child Nursing: Prenatal Diagnostic Tests

Indications for Prenatal Diagnostic Tests

  • Detection of congenital abnormalities

  • Evaluating the condition of the fetus

    • For high-risk pregnancies

    • Allows for appropriate interventions

  • Providing baseline information

    • Accurate gestational age

Types of Prenatal Tests (1 of 2)

  • Ultrasound

  • Doppler ultrasound (blood flow assessment)

  • Alpha-fetoprotein (AFP) screening

  • Multiple marker screening

  • Chorionic villus sampling (CVS)

  • Amniocentesis

Types of Prenatal Tests (2 of 2)

  • Percutaneous umbilical blood sampling (PUBS)

  • Antepartum fetal surveillance:

    • Nonstress test (NST)

    • Vibroacoustic stimulation test

    • Contraction stress test (CST)

    • Biophysical profile (BPP)

    • Modified biophysical profile

    • Maternal assessment of fetal movement

Ultrasound Applications

  • Used to determine fetal and placental conditions, including:

    • Presence and location of pregnancy

    • Multifetal gestation

    • Gestational age

    • Viability confirmation

    • Identifying fetal abnormalities

  • Emotional responses related to ultrasound results; fetal sex determination may not always be possible.

Doppler Ultrasound Blood Flow Assessment

  • Utilizes ultrasound to measure fetal blood flow.

  • Doppler shift is used especially in cases of:

    • Hypertension

    • Fetal growth restriction

    • Placental insufficiency

  • Measures the systolic to diastolic ratio.

Alpha-Fetoprotein Screening

  • Conducted on maternal serum or amniotic fluid to identify:

    • Open body wall defects (neural tube defects)

    • Chromosomal anomalies (like trisomy 21)

  • Ideal timing: between 16-18 weeks of gestation.

  • Requires only a blood sample; considered a preliminary test.

Multiple Marker Screening

  • Incorporates additional markers:

    • Human chorionic gonadotropin (hCG)

    • Unconjugated estriol

  • Enhances detection rates for trisomy 18 and 21.

  • Positive results typically lead to recommendations for amniocentesis.

Chorionic Villus Sampling (CVS)

  • Involves transcervical or transabdominal sampling of chorionic villi.

  • Can be performed earlier than amniocentesis (between 10-13 weeks gestation).

  • Provides information on chromosomal defects, metabolic or DNA abnormalities.

Amniocentesis Procedure

  • Involves aspiration of amniotic fluid for examination.

  • Second trimester amniocentesis:

    • Performed between 15-20 weeks for chromosomal or biochemical abnormalities.

  • Third trimester amniocentesis:

    • Used to determine fetal lung maturity or assess hemolytic disease.

Indications for Second Trimester Amniocentesis:

  • Maternal age 35 or older

  • Chromosomal abnormalities in close family members

  • Gender determination for X-linked disorders

  • Previous infant with a chromosomal abnormality

  • Multiple spontaneous abortions

  • Unexplained elevation of maternal-fetal alpha protein

  • Maternal Rh sensitization (Rh-negative mother/Rh-positive fetus).

Percutaneous Umbilical Blood Sampling (PUBS)

  • Also known as cordocentesis

  • Involves aspiration of fetal blood from the umbilical cord for prenatal diagnosis or therapy.

  • Used to detect blood disorders, acid-base imbalance, infection, or fetal genetic disease.

Antepartum Fetal Surveillance (1 of 2)

Nonstress Test (NST):

  • Evaluates fetal heart rate (FHR) accelerations, with or without movement.

  • FHR reactivity indicates adequate oxygen and intact neural pathways; may not develop until 32 weeks gestation.

Antepartum Fetal Surveillance (2 of 2)

Contraction Stress Test (CST):

  • Also known as the oxytocin challenge test

  • Assesses fetal heart response during contractions that reduce blood flow.

  • Cannot be performed if contractions are contraindicated; stimulation can be done via nipple stimulation or low-dose oxytocin.

Biophysical Profile (BPP)

  • Assesses five parameters:

    • Nonstress test (NST)

    • Fetal breathing movements

    • Gross fetal movements

    • Fetal tone

    • Amniotic fluid volume

  • Amniotic fluid index (AFI) quantifies amniotic fluid using ultrasound.

BPP Scoring:

  • Normal score (8-10) if AFI is adequate

  • Equivocal score (6)

  • Abnormal score (<4) with oligohydramnios suggests labor induction.

Effects of Hypoxemia and Fetal Acidosis

  • Late decelerations appear first as a sign of compromise.

  • Fetal breathing movements cease followed by cessation of fetal movement and tone.

Maternal Assessment of Fetal Movement

  • Movements are assessed by the mother, referred to as “kick counts.”

  • Recommended methods include:

    • At least 10 fetal movements within 12 hours

    • 5–10 movements per hour.

Patient Assessment Prior to Diagnostic Testing (1 of 2)

  • Obstetrical history: Gravida, para, living children, gestation

  • Maternal health problems

  • Current and prior obstetric issues

  • History of substance abuse (alcohol, tobacco).

Patient Assessment Prior to Diagnostic Testing (2 of 2)

  • Patient understanding of the test and reasons behind it

  • Knowledge regarding the surveillance regimen for further testing

  • Emotional responses to the test

  • Expectations of the test from patient and partner.