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PATH 406 > Pregnancy Monitoring > Flashcards

Pregnancy Monitoring Flashcards

1
Q

Where is hCG produced? What is its structure?

A

hCG - human chorionic gonadotropin

Chorion — contains trophoblasts which produce hCG and other placental hormones

Peak production 8-10 weeks

Structure
- a and b subunits, non-covalently bound
- Glycoprotein — branched CHO side chains
- a subunit same as TSH, LH, FSH
MW = 14900
- b subunit like LH b
MW = 23000
- In plasma, free a, free b, CGn and CGbCF
- Urine mainly CGbCF, some intact hCG, some CGn

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2
Q

State the clinical utility of glucose tolerance test.

A

Performed at 24-28 weeks gestation
- Overnight fast of at least 8 h
- 75 g consumed within 5 mins
- Blood collection before drink, then 1 hr and 2 hr after drink finished
- Any cutoff value exceeded is diagnostic of GDM
➔ Fasting > or = 5.1 mmol/L
➔ 1 hr > or = 10 mmol/L
➔ 2 hr > or = 8.5 mmol/L

Difference with regular oral glucose tolerance test
➔ Additional 1 hr sample
➔ Lower glucose cutoffs
- Increased insulin secretion & enhanced tissue sensitivity to insulin
- Placenta metabolizes/transport 50-75% of maternal glucose

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3
Q

State the clinical utility of fetal fibronectin test.

A

Used to test for preterm labour
- Extracellular protein that glues chorion to decidua
- POCT

Sensitivity = 70%
Specificity = 90%
+ve Test = 50% chance of preterm labour
-ve Test = 95% chance of no delivery

ALL patients who come for assessment for possible preterm labour
➔ 90% have no delivery in next 7 days

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4
Q

What are the endocrine changes that occur during pregnancy?

A
  1. Shift to supply nutrients to fetus
  2. Preparation of maternal physiology for
    - Maintenance of pregnancy
    - Delivery
    - Lactation
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5
Q

What is needed to mediate the endocrine changes that occur during pregnancy?

A

Corpus luteum — estrogen & progesterone
Placenta — Hormones, cytokines
Fetal hormones

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6
Q

What is the mechanism to initiate hormonal changes in pregnancy?

A

Embryo implantation induces trophoblast differentiation into HCG producing cells
- HCG maintains corpus luteum beyond 2 weeks
- Placenta becomes major source of estrogen & progesterone

Placental Inhibin A production
- Suppress pituitary LH, FSH ➔ no gonadal development during pregnancy

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7
Q

What does the placenta provide the fetus with? What does the mother require during pregnancy?

A

Healthy placenta provides fetus with
- Amniotic fluid
- Nutrients — glucose, aa, lipids, minerals, trace elements, vitamins
- Adequate gas exchange
- Clearance of toxic metabolic products — bilirubin, urea, ammonia

Health mother must acquire
- Nutrient stores
- Protection against blood loss in delivery

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8
Q

What are the maternal adaptive mechanisms?

A
  1. Plasma volume expansion
  2. Altered cardiac output and blood flow
  3. Increase GFR
  4. Expanded erythrocyte mass
  5. Hepatic protein synthesis
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9
Q

What are the hormonal changes that take place in pregnancy?

A
  • Progesterone for early embryonic growth is 5-20x above non-pregnant women
  • Estrogens (estrone, estradiol, estriol)
  • Placental-peptide hormones
    • hCG — human chorionic gonadotropin
    • hPL/hCS — placental lactogen or chorionic somatomammotropin
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10
Q

What is progesterone produced by during pregnancy? What is the function?

A

Produced: 1st corpus luteum (50 d), then placenta
Function
- *Inhibits smooth muscle tone
- Vascular impact — peripheral vascular smooth muscle tone resulting from decreased sensitivity to angiotensin II
- Stimulates hyperventilation — respiratory alkalosis

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11
Q

What is the action of estrogens during pregnancy?

A
  1. Endometrial development
  2. Blood supply
  3. Uterine muscle growth — preparation for delivery
  4. Hepatic protein synthesis
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12
Q

What is E3 a marker for?

A

Fetal and placental well being

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13
Q

What is a polypeptide similar to growth hormone during pregnancy? Function?

A

Placental lactogen
- Spares glucose for fetal utilisation

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14
Q

What is hCG function?

A
  1. Maintain corpus luteum function
    - binds to ovarian LH receptor
  2. a subunit acts in signal transduction (via cAMP)
    - promote progesterone production required for maintaining endometrium
  3. hCG > 1000000 U/L is thyrotropic
    - hCG can bind and activate TSH receptor
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15
Q

What are the hemodynamic changes in pregnancy?

A
  1. Total body water increase 4-6 L
  2. Blood volume 45% increase
  3. Dilutional effect on some analytes
  4. Net decrease in Hgb concentration
  5. Low Hgb results in lower viscosity
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16
Q

What are the causes of plasma volume increase?

A
  1. Anatomic changes
    ➔ decrease in vascular smooth muscle tone due to progesterone — low blood pressure
  2. Renin-angiotension-aldosterone axis
    ➔ activated to compensate for low BP
    ➔ estrogens incr liver synthesis of angiontensiongen
    ➔ incr water retention
17
Q

What changes does the heart go through in pregnancy?

A
  1. Cardiac output increases 30-40%
  2. Extra flow mainly goes to uterus/placenta
18
Q

What changes does the kidney go through in pregnancy?

A
  1. Renal blood flow increases 50%
  2. GFR 50% above non-pregnant by 20 weeks
    - Plasma urea and creatinine lower
    - Tubular reabsorption of glucose, aa, protein decr
19
Q

What changes does the lungs go through in pregnancy?

A
  1. Respiration stimulated by progesterone
  2. Respiratory alkalosis
  3. Slight decrease in pCO2, HCO3 ➔ incr pH
20
Q

What is the most common liver disease of pregnancy? List when presentation occurs, what is the clinical presentation, pathobiology, risk, treatment.

A

Intrahepatic Cholestasis of Pregnancy

Presentation
- Late second or early trimester
- Generalized itching, initially palms of hands and soles of feet, fat malabsorption, steatorrhea, Vit deficiency

Pathobiology: unclear — bile acid transporter genes in liver and high estrogen co-contribute: subsequent pregnancy 60-70% recurrence

Risk: Intrauterine fetal demise, spontaneous preterm birth or stillbirth

Treatment — ursodeoxycholic acid (UDCA)

21
Q

What is the most sensitive indicator of intrahepatic cholestasis of pregnancy (ICP)? What are other indicators?

A

Most sensitive ➔ total bile acids (umol/L, fasting)
- May increase >10x in ICP

Other ➔ cholic acid
- less commonly available
- may increase >10x in severe cases of ICP

22
Q

How to diagnose and date pregnancy?

A

Physical examination
1. History — last menstrual period
2. Ultrasound — dating optimal 8-14 weeks
3. Physical exam

Laboratory
1. Urinary hCG (qualitative) — 25 IU/L detected 1 week after missed period
➔ do this test if u would like to know
2. Serum hCG (quantitative) — 5 IU/L (8-11d post-conception)
➔ do this test if NEED to know definitively now

23
Q

When is hCG detectable?

A

3 1/2 weeks when placenta produces measurable hCG

24
Q

What are the pregnancy diagnostic pitfalls?

A

Lack of sensitivity of an hCG test — false negative
1. Pre-analytical
- mislabel, dilute urine, urine test too early
2. Analytical
- test Ab is relatively insensitive to hyperglycosylated form of hCG
3. Post-analytical
- reporting error

Lack of specificity of hCG test — false positive
1. Pre-analytical
- mislabel, sample collected on a peri/post menopausal women, patient with hCG producing tumour, early pregnancy loss, fertility treatment
2. Analytical
- Heterophilic Ab (serum)
- Historical — post menopausal woman w/ very high LH had cross reactivity with hCG test
3. Post-analytical
- reporting error

25
Q

What is ectopic pregnancy? How to detect ectopic pregnancy?

A

Implantation occurs outside uterus, usually fallopian tube
- Ectopic pregnancies are not normally viable
- Risk of rupture leading to internal bleeding, death is rare

Detection
- Clinical symptoms of ectopic pregnancy ➔ abdominal pain, bleeding
- Diagnostic imaging
➔ no gestational sac on U/S 24 d after conception if dating known
➔ no gestational sac if serum hCG > 3000 IU/L
- hCG may be low or undetectable
- Normal ➔ doubling time every 48h for first 5 weeks, after 5 weeks doubling time increases to 2-3 d

26
Q

How to differentiate ectopic/non-viable pregnancy from normal pregnancy?

A

On a graph (y-axis = hCG, x-axis = time)
- Bigger slope = normal
- Smaller slope = ectopic/non-viable

27
Q

What is gestational diabetes? What are the complications? How to identify? Treatment?

A

Diabetes of pregnancy

Complications for fetus:
1. Large fetus
2. Sudden intrauterine death
3. Neonatal death from prematurity
4. Respiratory distress syndrome
5. Newborn hypoglycemia

Complications for mother:
1. 20-50% chance of mother developing type 2 diabetes within decade

Identify with obstetric glucose tolerance test.

Manage with lifestyle therapy (insulin in overt cases)

28
Q

What are the clinical issues of preterm labour?

A
  1. Impt to transfer mother to an appropriate medical centre if pre-term delivery expected to allow access to:
    - Neonatal specialists
    - Incubators
    - Ventilators
  2. Difficult to predict which patients will go into labour
    - Traditional tests may not be definitive

PATH 406 (24 decks)

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