Pregnancy Flashcards
The concentration of ________ in amniotic fluid is a reflection on the severity of fetal hemolysis.
Unconjugated bilirubin
What is the maximal absorbance of bilirubin, when assessing by scanning spectrophotometry?
450 nm
What are two important factors for Amniotic fluid specimen collection?
- Blood contamination (absorbance peak of oxyhemoglobin at 410 nm can affect magnitude of peak at 450 nm)
- Protected from light (causes degradation of bilirubin)
What produces Human chorionic gonadotropin?
- Placenta
- Tumors
- Pituitary gland (small amounts during menopause)
What is the structure of hCG?
-What shares same structure?
Heterodimer of a alpha and a beta chain
- Alpha chain same as TSH, FSH, LH
- Beta chain is unique
A false positive hCG is most often due to what?
Heterophile antibody interference
- When does hCG become detectable?
- What are the levels?
- 6-8 days post-conception
- 10-50 mIU/mL
- In normal pregnancy, hCG should double how often?
- When does it peak?
- 48 hours
- End of first trimester
*Decreases gradually and by early 2nd trimester plateus
An abnormal hCG dynamic is defined as what?
What does this suggest?
- Failure to rise 66% in 48 hours
- Ectopic or nonviable intrauterine pregnancy
*20% of ectopic show normal rise
After removal of an ectopic pregnancy, how long does hCG normally remain elevated?
Several weeks
An abnormally high hCG is seen in what condition?
Gestational Trophoblastic disease (GTD)
-Molar pregnancy
hCG is typically higher in complete or partial moles?
Complete moles have higher hCG
What is the management following evacuation of a molar pregnancy?
- hCG levels monitored Weekly until undetectable for 3 consecutive weeks
- Then measured monthly for 1 year
After evacuation of an uncomplicated molar pregnancy, how long does hCG remain detectable?
-When should persistent GTD be suspected?
10 weeks
-if hCG plateaus or rises, then persistent GTD is supected
Quad Screen:
-Markers
Markers:
- Maternal serum hCG
- a-fetoprotein (AFP)
- unconjugated Estriol (uE)
- Inhibin A (DIA)
Quad Screen:
- When
- How is risk calculated
- Sensitivity for Downs
- 2nd trimester (18 weeks)
- Analytes and maternal age
- 78%
1st Trimester Test:
- Markers
- Sensitivity
- Time
- hCG
- PAPP-A
- Nuchal fold translucency (NT) thickness
- When combined with maternal age, overall sensitivity is 83%
- 10-13 weeks
In Downs, is the Nuchal Fold Transulcency Thickness increased or decreased?
Increased
What is the serum Integrated Screen?
-Sensitivity
Combined 1st and 2nd trimester serum testing
-when combined with maternal age and NT, overall sensitivity is 88%
Quad screen levels in trisomy 21 (Downs).
- hCG - High
- AFP - Low
- Estriol - Low
- Inhibin - High
Quad screen levels in trisomy 18 (Edward syndrome).
- hCG - Low
- AFP - Low
- Estriol - Low
Quad screen levels in neural tube defect (NTD).
- hCG - Normal
- AFP - High
- Estriol - Low
T/F: Bacterial vaginosis is independently associated with preterm labor.
True
What is true regarding Fetal Fibronectin and preterm birth.
Absence of FF has very high Negative Predictive value and can exclude impending preterm birth.
*A positive result suggests preterm labor, but the overall PPV is low
Where is fetal fibronectin normally found?
Placental fetomaternal surface
What other test has similar diagnostic accuracy to fetal fibronectin?
Cervical Length assessed by Transvaginal Cervical US
When is fetal lung maturity (FLM) generally achieved?
37 weeks gestation
What has an accelerating effect on FLM?
Excess corticosteroids
-stress of complicated pregnancy
What effect does maternal DM have on FLM?
Delays
What is the Lecithin/Sphingomyelin ratio that indicates FLM?
> 2.5:1 (F/S ratio)
In pregnancies complicated by maternal diabetes, a ratio of 2.5:1 (L/S) is less predictive of FLM. WHat test is more reliable in this setting?
Phosphatidylglycerol concentration
What effect does meconium have on the L:S ratio?
-Blood?
Falsely decreases
*Blood normalizes the L:S ratio to ~1.5
When is Phosphatidylglycerol (PG) first detected? What is its significance?
- 35-36 weeks
- Presence is indicative of FLM
What effect does blood and meconium have on PG?
No effect
*however, PG is a late marker for FLM, which limits its utility in prematurity
Surfactant Lamellar Bodies (LBC):
- How are they counted?
- What level is predictive of FLM?
- Blood and Meconium effects?
- Same size as platelets (use platelet channel of cell counter)
- LBC >50,000
- Blood - Decreases LBC
- Meconium - Increases LBC
T/F: Estrogen causes an increase in transport proteins such as thyroid binding globulin (TBG).
True
When does relative insulin resistance emerge in pregancy? What causes this?
- early 3 trimester
- human Placental Lactogen (hPL) has antiinsulin effects similar to growth hormone
What happens to sodium and potassium levels throughout pregnancy?
remain relatively constant
What happens to calcium levels in pregnancy?
- Total calcium levels DECREASE (10%) d/t physiologic hypoalbuminemia
- Ionized calcium levels remain unchanged
What happens to Hct/Hb in pregnancy?
- Hct - decreases (4-7%)
- Hb - decreases (1.5-2 g/dL)
What happens to BUN in pregnancy?
Decreases (50%)
