Antepartal Tests

• Ultrasound for gestational age is determined through mea- surements of fetal–crown rump length, biparietal diameter, and femur length. It is most accurate when performed before 20 weeks’ gestation.
• Umbilical artery Doppler flow is a noninvasive screening technique that uses advanced ultrasound technology to assess resistance to blood flow in the placenta.
• Chorionic villus sampling (CVS) is aspiration of a small amount of placental tissue (chorion) for chromosomal, meta- bolic, or DNA testing. This test is used for chromosomal analysis between 10 and 12 weeks’ gestation to detect fetal abnormalities caused by genetic disorders.
• Amniocentesis involves insertion of a needle into the amniotic sac to remove fluid for chromosome studies, alpha-fetoprotein levels, lung maturity, and other tests.
• Fetal fibronectin (FN) is a protein found on the surface of the fetal membranes. FN is normally present during pregnancy but disappears at term labor. A positive result indicates premature rupture of membranes.
• Nonstress test measures fetal heart rate response to fetal movement. The baby must move every 30 minutes; if there are no movements within this time frame, it may indicate fetal distress.
• Amniocentesis is a diagnostic procedure in which a needle is inserted through the maternal abdominal wall into the uterine cavity to obtain amniotic fluid. It is commonly performed for genetic testing, assessment of fetal lung maturity, and assessment of hemolytic disease in fetus or for intrauterine infection.
• ■ L:S ratio >2:1 indicates fetal lung maturity.

  ■ L:S ratio <2:1 indicates fetal lung immaturity in increased risk of respiratory distress syndrome.

  ■ Positive PG indicates fetal lung maturity.

  ■ Negative PG indicates immature fetal lungs.

  ■ A LBC of ≥50,000/μL is highly indicative of fetal lung

  maturity.

  ■ A LBC of ≤15,000/μL highly indicative of fetal lung

  immaturity.
• The fern test is a microscopic slide test to determine the presence of amniotic fluid leakage. Using sterile technique, a specimen is obtained from the external os of the cervix and vaginal pool and is examined on a slide under a micro- scope.
• A negative fern test does not show any evidence of amniotic fluid leakage.
• A positive fern test shows the presence of amniotic fluid with squamous epithelial cells that resemble the fronds of a fern when viewed under a microscope.
• A nitrazine test strip is used to detect the presence of amniotic fluid in vaginal secretions.
• Negative Contraction Stress Test (Normal)

  A negative result is represented by no late decelerations of the fetal heart rate (FHR).
• Positive Contraction Stress Test (Abnormal)

  A positive result is represented by late decelerations of the FHR, with 50% or more of the contractions in the absence of hyperstimulation of the uterus.
• An equivocal result contains decelerations, but with less than 50% of the contractions, or uterine activity shows a hyperstimulated uterus.
• An unsatisfactory result means that adequate uterine contractions cannot be achieved, or the FHR tracing is of insufficient quality for adequate interpretation.
• Human chorionic gonadotropin (hCG): a hormone produced by the placenta

  Alpha-fetoprotein (AFP): a protein produced by the fetus

  Estriol: a protein produced by the fetus and placenta Inhibin A: a protein produced by the ovaries and placenta
• Low levels of AFP can indicate a risk for Down syndrome.
• High levels of AFP can indicate a risk for neural tube defects.
• The NST is interpreted as reactive if the FHR is a normal baseline rate with moderate variability, accelerates at least 15/min (10/min prior to 32 weeks) for at least 15 seconds (10 seconds prior to 32 weeks) and occurs two or more times during a 20-min period.
• NEGATIVE CST (NORMAL FINDING): Indicated if within a 10-min period, with three uterine contractions, there are no late decelerations of the FHR.
• POSITIVE CST (ABNORMAL FINDING): Indicated with persistent and consistent late decelerations with 50%

  or more of the contractions. This is suggestive of uteroplacental insufficiency.
• Variable deceleration can indicate cord compression.
• Prolonged deceleration can indicate hypoxia.
• Late deceleration can indicate utero placental insufficiency.
• Early deceleration can indicate fetal head compression.
• AFP can be measured from the amniotic fluid between 15 and 20 weeks and can be used to assess for neural tube defects in the fetus or chromosomal disorders.
• High levels of AFP is associated with NTB, such as anencephaly (incomplete development of fetal skill and brain), spina bifida (open spine), or omphalocele (abdominal wall defects.) High AFP levels also can be present with normal multifetal pregnancies.
• Low levels of AFP is associated with chromosomal disorders (Down syndrome) or gestational trophoblastic disease (hydatidiform mole).
• Percutaneous umbilical blood sampling, commonly called cordocentesis, is the most common method used for fetal blood sampling and transfusion.
• Kleihauer-Betke test is done to detect the presence and amount of fetal blood in the maternal circulation and to identify clients who need additional Rho(D) immune globulin.
• Kleihauer-Betke test in maternal blood may be positive and indicate the presence of fetal red blood cells.
• A karyotype is an organized arrangement of all the chromosomes present in a cell during the metaphase section of mitosis
• Chorionic villus sampling (CVS) involves removing chorionic tissue from the placenta through a catheter inserted into the uterine cavity via the vagina or abdomen.
• Amniocentesis is performed between weeks 14 and 20 of pregnancy by inserting a needle through the mother's abdomen into the amniotic sac to remove fluid containing fetal cells.
• Biophysical Profile determined fetal well being. It is an ultrasonography that is used to evaluate fetal health being by assessing 5 variables:

  1. Gross body movements
  2. Reactivity of FHR
  3. Amniotic fluid volume
  4. Fetal tone
  5. Fetal breathing movements
• Nonstress Test measures fetal heart rate response to fetal movement, which indicates fetal wellbeing. The nonstress test is usually done at least twice weekly starting around week 36 of gestation until delivery.
• The purpose of the stress test is to determine if there is adequate oxygen supply to the baby when contractions occur.
• Contraction Stress Test is also known as Oxytocin Challenge Test.
• In a nonstress test, a healthy fetus will usually respond to its own movements by means of an FHR acceleration of 15 beats, lasting for at least 15 seconds after the movement, twice in a 20 minute period.