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Year 2 OBGYN > Isoimmunization and multifetal gestation > Flashcards

Isoimmunization and multifetal gestation Flashcards

1
Q

definition: isoimmunization

A

immune response generated in an individual of one species by an alloantigen from a different individual of the same species

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2
Q

what is Rh disease?

A

occurs during pregnancy when there is n nincompatibility between the blood types of the mother and fetus

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3
Q

what is the inheritance pattern of Rh factor?

A

autosomal dominant

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4
Q

where is the maternal immune response to Rh generated?

A

spleen

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5
Q

what is the reason for neonatal jaundice as a result of Rh incompatibility?

A

fetus does not have glucoronyl transferase to conjugate indirect bilrubin

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6
Q

when is screening done for Rh status?

A
  • first prenatal visit
  • 28 weeks
  • postpartum
  • antepartum bleeding and before giving any Ig
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7
Q

what are the gold standard tests for Rh status?

A
  • indirect Coombs

- direct Coombs

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8
Q

what is the indirect Coombs test?

A
  • mix Rh(D)+ cells with maternal serum
  • anti-Rh(D) ab will adhere
  • RBCs then washed ans suspended in Coombs serum (antihuman Ig)
  • RBCs coated with ab will be agglutinated
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9
Q

what is the direct Coombs test?

A
  • mix infants RBCs with Coombs serum

- maternal ab present if cells agglutinate

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10
Q

what is the +Rh(D) antibody screen?

A
  • serial ab titres q2-4 weeks
  • if titre over 1:16 - get amniocentesis or MCA dopplers
  • critical titre: significant risk of hydrops
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11
Q

what is the critical titre?

A

serial antidoby titres for Rh indicating significant risk for hydrops

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12
Q

what test is performed if there is a previously affected infant or critical titres are known?

A

amniocentesis

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13
Q

what is the significance of the zones on the Liley curve?

A

zone 1 - fetus very low risk of severe fetal anemia

zone 2 - mild to moderate risk of fetal hemolysis

zone 3 - severe fetal anemia with high probability of fetal death within 7-10 days

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14
Q

when is the Liley curve considered accurate?

A

after 27 weeks

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15
Q

how does the anemic fetus preserve oxygen delivery to the brain?

A

increasing flow

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16
Q

how is fetal anemia diagnosed?

A
  • amniocentesis
  • cordocentesis
  • US
17
Q

what are the treatment options for a fetus at risk of fetal anemia?

A
  • intravascular fetal transfusion

- preterm birth

18
Q

what are the results of Rh incompatibility?

A
  • intrauterine fetal demise
  • live born neonate appears pale, edematous, limp
  • hyperbilirubinemia can lead to jaundice and neurotoxic effects
19
Q

what are the treatment options for a fetus at risk of Rh incompatibility?

A
  • phototherapy

- exchange or direct blood transfusion

20
Q

what is RhoGAM?

A

anti-D Ig

21
Q

what is the kleihauer-betke test? how does it work?

A
  • % of fetal RBC in maternal circulation
  • fetal RBCs contain HbF which is more resistant to acid elution than HbA so after exposure to acid, only fetal cells remain and can be identified with stain
22
Q

how do dizygotic twins (fraternal) occur?

A

two separate ova fertilized by two separate sperm

23
Q

how do monozygotic twins (identical) occur?

A

division of a fertilized ovum AFTER conception (1 in 250)

24
Q

how do diamniotic / dichorionic twins occur?

A

division of the conceptus within 3 days of fertilization

25
Q

how do diamniotic / monochorionic twins occur?

A
  • division occurs between 4-8 days

- chorion has already begun to develop but amnion has not

26
Q

how do monoamniotic / monochorionic twins occur?

A
  • division occurs between 9-12 days after development of both amnion and chorion so they share a common sac
  • occurs in 1 in 10,000
27
Q

how do conjoined twins occur?

A
  • division occurs incompletely

- 1 in 70,000

28
Q

how is diagnosis made for multifetal gestation?

A
  • size > dates on exam

- US at 9-10 weeks

29
Q

when is chorionicity determined? what test?

A

9-10 weeks by US

30
Q

what are the main risk / complication with multiple gestation?

A

preterm labor and delivery

31
Q

twin-twin transfusion syndrome occurs in what type of multifetal gestation?

A

monochorionic > dichorionic

32
Q

what are the morbidities / mortalities associated with monochorionic and dichorionic gestations?

A
  • twin-twin transfusion syndrome
  • cord entaglement
  • fetal death
33
Q

which carries more risk of morbidity / mortality: monochorionic or dichorionic gestation?

A

monochorionic

34
Q

what is the etiology of twin-twin transfusion syndrome?

A

arterio-venous anastamosis between fetuses

35
Q

what happens to the donor twin in twin-twin transfusion syndrome? recipient twin?

A
  • donor twin: imparied growth, anemia, hypovolemia, oligohydramnios
  • recipient twin: hypervolemia, HTN, polycythemia, high output CHF, polyhydramnios

Year 2 OBGYN (33 decks)

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