Diagnostic Tests to Evaluate Fetal Well-being

Test Implications of Results Risks
Nonstress Test (NST)
  • Requires electronic fetal monitoring
  • Correlates fetal movements with FHR and intact fetal CNS; 90% of gross fetal movements associated with accelerations of the FHR
  • Reactive test - indicates intact CNS.
  • Nonreactive test - does not meet criteria for reactivity. May indicate fetal jeopardy.
  • Noninvasive procedure
  • No known contraindications
Contraction Stress Test (CST)
Correlates fetal heart rate response to induced uterine contractions; indicator of uteroplacental insufficiency
  • Increased doses of oxytocin are administered to stimulate uterine contractions. Interpretation:
  • Negative results indicate absence of abnormal deceleration with all contractions. Reassurance that the fetus is likely to survive if labor occurs in I wk.
  • Positive results indicate abnormal FHR decelerations and that the fetus is at increased risk for perinatal morbidity and death
  • Invasive procedure
  • Risk for uterine hyperstimulation and jeopardy to the fetus.
Ultrasound
Passage of high-frequency sound waves through uterus to obtain data regarding fetal growth, placental position, and uterine cavity; can be done abdominally or vaginally May be used for: pregnancy confirmation, fetal viability, estimation of fetal age, placental location, detection of fetal abnormalities, identification of multiple gestation, and confirmation of fetal death.
  • Noninvasive procedure
  • Inconclusive evidence of harmful effects on humans
Biophysical Profile (BPP)
Assessment of five fetal biophysical variables: tone, breathing movements, gross body FHR reactivity (NST); first four variables assessed by ultrasound; score of 2 assigned to each normal finding, and 0 to each abnormal; maximum score 10
  • Used to assess the fetus at risk for intrauterine compromise.
  • Normal fetal biophysical activities indicate that the CNS is functional and the fetus is not hypoxemic.
  • Abnormal findings with oligohydramnios indicate fetal jeopardy (acidosis and impending death) and necessity for immediate delivery.
  • Normal: 8-10 (if amniotic fluid volume (AFV) adequate).
  • Equivocal: 6.
  • Abnormal: <4.
  • Noninvasive procedures
  • No known contraindications
Amniocentesis
Invasive procedure for amniotic fluid analysis; needle placed through abdominal wall to obtain designated amount of fluid for examination; ultrasound always precedes this procedure; possible after 14 weeks of gestation Amniotic fluid (fetal cells) might be analyzed for chromosomal studies to detect: aberrations, inborn errors of metabolism; determine fetal lung maturity, fetal age, presence of isoimmune disease, alpha-fetoprotein (AFP) levels for determination of neural tube defects, and presence of meconium.
  • Complications: < l%,but risks might include: onset of contractions, infections; placental, cord, fetal, or bladder puncture
  • Fetomaternal hemorrhage with possible Rh isoimmunization
  • Rh negative mothers should receive RhoGAM following the procedure
Percutaneous Umbilical Blood Sampling (PUBS; also called cordocentesis)
Technique used to obtain pure fetal blood from the umbilical cord while the fetus is in utero; ultrasound done first to locate umbilical cord, then a needle is inserted through the maternal abdomen and into the fetal umbilical vein; done in second and third trimesters; a paralytic agent, such as Pavulon, may be given to prevent fetal movement during the procedure Indications for fetal blood sampling:
  • Rapid fetal karyotyping.
  • Diagnosis of fetal infection.
  • Platelet disorders.
  • Fetal blood grouping.
  • Diagnosis and treatment of isoimmunization.
  • Assessment of fetal well-being (pH, Po,).
  • Fetal metabolic disorders.
  • Fetal blood transfusion.
  • Administration of fetal medications.
Overall fetal loss risk <2%; complication rate after PUBS: Complications include: mature rupture of membranes, chorioamnionitis, fetal bradycardia, Rh isoimmunization (Rh negative women given RhoGAM).
Chorionic Villus Sampling (CVS)
Involves obtaining a small sample of chorionic villi from edge of developing placenta between 10 and 12 weeks of gestation; can be accomplished either transcervically or transabdominally; use sterile procedure; chorionic tissue aspirated into a syringe Because chorionic villi originate in zygote, it reflects the genetic makeup of the fetus.
Indications for CVS:
  • Advance maternal age(>35year).
  • Biochemical and molecular assays for infections. Assays for metabolic disorders.
  • Assays for metabolic disorders.
 Vaginal bleeding, spontaneous abortion (SAB), rupture of membranes, limb anomalies (increased risk if done < 10 weeks of gestation); intrauterine infection, Rh isoimmunization (Rh negative women given RhoGAM)


Diagnostic Tests to Evaluate Fetal Well-being

Test Implications of Results Risks
Nonstress Test (NST)
  • Requires electronic fetal monitoring
  • Correlates fetal movements with FHR and intact fetal CNS; 90% of gross fetal movements associated with accelerations of the FHR
  • Reactive test - indicates intact CNS.
  • Nonreactive test - does not meet criteria for reactivity. May indicate fetal jeopardy.
  • Noninvasive procedure
  • No known contraindications
Contraction Stress Test (CST)
Correlates fetal heart rate response to induced uterine contractions; indicator of uteroplacental insufficiency
  • Increased doses of oxytocin are administered to stimulate uterine contractions. Interpretation:
  • Negative results indicate absence of abnormal deceleration with all contractions. Reassurance that the fetus is likely to survive if labor occurs in I wk.
  • Positive results indicate abnormal FHR decelerations and that the fetus is at increased risk for perinatal morbidity and death
  • Invasive procedure
  • Risk for uterine hyperstimulation and jeopardy to the fetus.
Ultrasound
Passage of high-frequency sound waves through uterus to obtain data regarding fetal growth, placental position, and uterine cavity; can be done abdominally or vaginally May be used for: pregnancy confirmation, fetal viability, estimation of fetal age, placental location, detection of fetal abnormalities, identification of multiple gestation, and confirmation of fetal death.
  • Noninvasive procedure
  • Inconclusive evidence of harmful effects on humans
Biophysical Profile (BPP)
Assessment of five fetal biophysical variables: tone, breathing movements, gross body FHR reactivity (NST); first four variables assessed by ultrasound; score of 2 assigned to each normal finding, and 0 to each abnormal; maximum score 10
  • Used to assess the fetus at risk for intrauterine compromise.
  • Normal fetal biophysical activities indicate that the CNS is functional and the fetus is not hypoxemic.
  • Abnormal findings with oligohydramnios indicate fetal jeopardy (acidosis and impending death) and necessity for immediate delivery.
  • Normal: 8-10 (if amniotic fluid volume (AFV) adequate).
  • Equivocal: 6.
  • Abnormal: <4.
  • Noninvasive procedures
  • No known contraindications
Amniocentesis
Invasive procedure for amniotic fluid analysis; needle placed through abdominal wall to obtain designated amount of fluid for examination; ultrasound always precedes this procedure; possible after 14 weeks of gestation Amniotic fluid (fetal cells) might be analyzed for chromosomal studies to detect: aberrations, inborn errors of metabolism; determine fetal lung maturity, fetal age, presence of isoimmune disease, alpha-fetoprotein (AFP) levels for determination of neural tube defects, and presence of meconium.
  • Complications: < l%,but risks might include: onset of contractions, infections; placental, cord, fetal, or bladder puncture
  • Fetomaternal hemorrhage with possible Rh isoimmunization
  • Rh negative mothers should receive RhoGAM following the procedure
Percutaneous Umbilical Blood Sampling (PUBS; also called cordocentesis)
Technique used to obtain pure fetal blood from the umbilical cord while the fetus is in utero; ultrasound done first to locate umbilical cord, then a needle is inserted through the maternal abdomen and into the fetal umbilical vein; done in second and third trimesters; a paralytic agent, such as Pavulon, may be given to prevent fetal movement during the procedure Indications for fetal blood sampling:
  • Rapid fetal karyotyping.
  • Diagnosis of fetal infection.
  • Platelet disorders.
  • Fetal blood grouping.
  • Diagnosis and treatment of isoimmunization.
  • Assessment of fetal well-being (pH, Po,).
  • Fetal metabolic disorders.
  • Fetal blood transfusion.
  • Administration of fetal medications.
Overall fetal loss risk <2%; complication rate after PUBS: Complications include: mature rupture of membranes, chorioamnionitis, fetal bradycardia, Rh isoimmunization (Rh negative women given RhoGAM).
Chorionic Villus Sampling (CVS)
Involves obtaining a small sample of chorionic villi from edge of developing placenta between 10 and 12 weeks of gestation; can be accomplished either transcervically or transabdominally; use sterile procedure; chorionic tissue aspirated into a syringe Because chorionic villi originate in zygote, it reflects the genetic makeup of the fetus.
Indications for CVS:
  • Advance maternal age(>35year).
  • Biochemical and molecular assays for infections. Assays for metabolic disorders.
  • Assays for metabolic disorders.
 Vaginal bleeding, spontaneous abortion (SAB), rupture of membranes, limb anomalies (increased risk if done < 10 weeks of gestation); intrauterine infection, Rh isoimmunization (Rh negative women given RhoGAM)