1.2 MTB Step 3 - The Uncomplicated Pregnancy (2nd & 3rd Trimester Prenatal Screening) Flashcards
Cards Complete:
SECOND TRIMESTER SCREENING
SAMPLE QUESTION
“A 23-yo woman (G3P1 Abortion 1) is seen at 17 weeks gestation. She recently underwent a triple marker screen with the maternal serum alpha-fetoprotein (normal < 2.5 MoM). Her test showed an elevation in maternal serum alpha-fetoprotein. On exam, her uterus is at the umbilicus.”
What is the Next Step in management?
Ultrasound
- The first step in evaluating any pregnancy with an abnormal MS-AFP is to get an Obstetric Ultrasound to confirm the gestational date.
SECOND TRIMESTER SCREENING
DEFINITION
- What do MS-AFP and MoM stand for?
- What is the combined significance in diagnostic testing?
Maternal Serum Alpha FetoProtein (MS-AFP) - increases with gestational age.
Multiples of the Median (MoM) - units for MS-AFP
- MS-AFP > 2.5 MoM = Elevated (abnormal)
- MS-AFP < 2.5 MoM = Normal
SECOND TRIMESTER SCREENING
DEFINITION
- What is the Importance of Inhibin A in pregnancy?
- What disorder is and abnormal Inhibin A level associated with, and is the level abnormal Increased or Decreased?
- Inhibin A - made by the Placenta during pregnancy and normally remains constant during 15th - 18th week of pregnancy.
- Inhibin A level is INCREASED in the Blood of Mothers of Fetuses with DOWN SYNDROME.
SECOND TRIMESTER SCREENING
GENERAL
What is the Most COMMON Cause of an Abnormal Maternal Serum Alpha FetoProtein (MS-AFP)?
Gestational Dating Error
SECOND TRIMESTER SCREENING
What is the (1) optional Second Trimester Screening test?
Quadruple Marker Screen
- MS-AFP (never test alone; only 20% sensitive by itself)
- Beta-hCG
- Estriol
- Inhibin A (only add in high-risk women. Increases sensitivity to 80%)
SECOND TRIMESTER SCREENING
What are (6) disorders associated with an Elevated MS-AFP?
Elevated MS-AFP:
- Neural Tube Defect (NTD)
- Ventral Wall Defect
- Twin Pregnancy
- Placental Bleeding
- Renal Disease
- Sacrococcygeal Teratoma
SECOND TRIMESTER SCREENING
What are (2) disorders associated with a Decreased MS-AFP and what are the Quadruple Marker Screening levels for each (MS-AFP, Estriol, Beta-hCG, Inhibin A)?
-
Trisomy 21 (Down Syndrome):
- Decreased MS-AFP
- Decreased Estriol
- Increased Beta-hCG
- Increased Inhibin A
-
Trisomy 18:
- Decreased MS-AFP
- Decreased Estriol
- Decreased Beta-hCG
- Decreased Inhibin A
SECOND TRIMESTER SCREENING
What is the First Step in Management for an Abnormal MS-AFP?
Ultrasound
- Perform Ultrasound to confirm dating.
- If dating error, repeat MS-AFP.
- A normal repeat MS-AFP is reassuring.
Note: Accurate gestational dating is needed for interpretation of results.
SECOND TRIMESTER SCREENING
What is the Next Step in Management for an Abnormal MS-AFP if gestational age is confirmed on Ultrasound?
For an Abnormal ELEVATION in MS-AFP, perform:
- Amniocentesis for Amniotic Fluid Alpha-FetoProtein (AF-AFP) level and Acetylcholinesterase activity.
- ELEVATED levels of Amniotic Fluid Acetylcholinesterase activity are specific to Open NTD.
For an Abnormal DECLINE in MS-AFP, perform:
- Amniocentesis for Karyotyping
THIRD TRIMESTER SCREENING
SAMPLE QUESTION
“A 38-yo woman (G2P1) is at 27-weeks’ gestation. She weighs 227 lbs. She has gained 30 lbs. during her pregnancy but reports that most of this is “fluid retention.” She was diagnosed with gestational diabetes during her last pregnancy.”
What is the Next Step in management?
1-hr 50g OGTT
- This is the First Step in evaluating for Gestational Diabetes.
- Performed in weeks 24 - 28 weeks gestation.
Abnormal Result: 1-hr Blood Glucose > 130 - 140 mg/dL
OGTT = Oral Glucose Tolerance Test
THIRD TRIMESTER SCREENING
What are (4) disorders that are Screened for during the Third Trimester?
- Diabetes
- Anemia
- Atypical Antibodies
- GBS
THIRD TRIMESTER SCREENING
GESTATIONAL DIABETES
- What is the Best Third Trimester screening test for Gestational Diabetes?
- What is considered an Abnormal Result on this test?
1-hr 50g OGTT
- This is the First Step in evaluating for Gestational Diabetes.
- Performed in weeks 24 - 28 weeks gestation.
Abnormal Result: 1-hr Blood Glucose > 130 - 140 mg/dL
OGTT = Oral Glucose Tolerance Test
THIRD TRIMESTER SCREENING
GESTATIONAL DIABETES
What is the Next BEST Step in management for a Positive initial screening test for Gestational Diabetes?
3-hr 100g OGTT
- The Confirmatory Test for Glucose Intolerance in pregnancy.
- Requires an overnight fast.
- Gestational Diabetes if 2 or more elevated values.
- Impaired Glucose Tolerance if 1 elevated value.
Abnormal Results:
- 1-hr Blood Glucose > 180 mg/dL
- 2-hr Blood Glucose > 155 mg/dL
- 3-hr Blood Glucose > 140 mg/dL
OGTT = Oral Glucose Tolerance Test
THIRD TRIMESTER SCREENING
ANEMIA
What is the Best Third Trimester screening test for Anemia?
CBC
- Measured at 24 - 28 weeks gestation.
THIRD TRIMESTER SCREENING
ANEMIA
- What is the Hemoglobin (Hb) value for Anemia on Third Trimester Screening?
- What is the Most COMMON Cause of Anemia in the Third Trimester?
- What is the treatment?
- Anemia = Hb < 11 g/dL
- Iron Deficiency
- Iron Supplementation