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RGU 2 > Isoimmunization, Multifetal Gestation & Fetal Growth Abnormalities > Flashcards

Isoimmunization, Multifetal Gestation & Fetal Growth Abnormalities Flashcards

1
Q

What is the average “menstrual or gestational” age of a developing fetus?

A

40 weeks (FDLMP to due date)

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2
Q

What is the average gestational age for twins?

A

35 weeks

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3
Q

What is the average gestational age for triplets?

A

33 weeks

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4
Q

What is the average gestational age for quadruplets?

A

29 weeks

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5
Q

What are the common complications of preterm delivery?

A
  • low birth weight
  • respiratory distress syndrome
  • neurologic impairment
  • intraventricular hemorrhage
  • necrotizing enterocolitis
  • retinopathy of prematurity
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6
Q

What are the complications of multiple gestations?

A
  • preterm complications
  • fetal growth restriction
  • preeclampsia/gestational DM
  • abruptio placentae
  • rupture of membranes leading to preterm delivery.
  • congenital anomalies
  • cerebral palsy
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7
Q

On what day after ovulation does the zygote (blastocyst) implant in the endometrial lining?

A

day 8

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8
Q

With what does maternal blood come into direct contact?

A

the CHORION

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9
Q

** What 2 layers comprise the sac that the baby grows in?

A
  • INNER AMNION (water bag).

- OUTER CHORION

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10
Q

*** What are DIZYGOTIC twins?

A
  • twins resulting from two separate fertilizations by two genetically dissimilar sperm with 2 genetically dissimilar oocytes.
  • aka you get 2 genetically different babies (FRATERNAL twins).
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11
Q

*** How are the membranes arranged for DIZYGOTIC twins?

A
  • each has their own INNER AMNION and OUTER CHORION.

* Dichorionic-Diamniotic placentation!

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12
Q

*** What are MONOZYGOTIC twins?

A
  • twins resulting from ovulation and fertilization of a SINLGE OOCYTE with subsequent division (cleavage) of the zygote.
  • aka IDENTICAL twins
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13
Q

** What determines the membrane division of monozygotic twins?

A

the TIMING of zygote cleavage.

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14
Q

** Are dizygotic twins ALWAYS dichorionic-diamniotic?

A

YES!!!

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15
Q

*** What is the placentation result of zygote cleavage (MONOZYGOTIC twins) within 4 days of fertilization, while still in the fallopian tube?

A
  • dichorionic-diamniotic
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16
Q

** What is the placentation result of zygote cleavage (MONOZYGOTIC twins) between days 4-8 after fertilization (typically while the blastocyst is in the uterine cavity)?

A
  • MONOchorionic-diamniotic
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17
Q

If you do an ultrasound and see a MONOchorionic-diamniotic placenta, what do you absolutely know?

A
  • babies are 100% MONOZYGOTIC twins

* aka identical twins

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18
Q

If you do an ultrasound and see a dichorionic-diamniotic placenta, what do you know?

A
  • babies could be either dizygotic or monozygotic.
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19
Q

** What is the placentation result of zygote cleavage (MONOZYGOTIC twins) between days 8-12 after fertilization?

A
  • MONOchorionic- MONOamniotic

* these babies have a higher rate of cord entanglement and complications.

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20
Q

*** What happens if zygote cleavage (MONOZYGOTIC twins) occurs after day 13 (after formation of the bilaminar disc)?

A

conjoined twins :(

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21
Q

*** Are all monochorionic twins identical?

A

YES

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22
Q

*** Are all dichorionic twins always dizygotic?

A

NO, could be monozygotic if division occurs within 4 days of fertilization.

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23
Q

*** Are all dizygotic twins always dichorionic?

A

YES

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24
Q

*** Can monochorionic twins be dizygotic?

A

NEVER, these are always identical twins.

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25
Q

Are most twins di- or mon-zygotic?

A
  • most are dizygotic
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26
Q

What type of placentation are most MONOzygotic twins?

A
  • 65%= MONOchorionic-diamniotic
  • 34%= dichorionic-diamniotic
  • 1%= MONOchorionic-MONOamniotic
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27
Q

** How do you tell chorionicity/amnionicity?

A
  1. count the # of placentas (if 2, then DC; if 1, then DC or MC).
  2. check gender (if different, then DC; if same, then DC or MC)
  3. check for LAMBDA SIGN= as two chorions come together they form a triangular appearance on US which is an intervening membrane that separates the 2 babies (always dichorionic-diamniotic).
  4. check for T-SIGN= no triangle appearance like lambda sign, but membrane goes straight in and is more consistent with monozygotic (MONOchorionic-diamniotic) preganancy.
  5. check membrane thickness (dichorionic-diamniotic makes a THICK membrane; MONOchorionic-diamniotic makes a THIN membrane, usually less than 2 mm).
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28
Q

If you don’t see an intervening membrane on US, but do see 2 separate yolk sacs, what can you infer about placentation?

A
  • MONOchorionic-diamniotic
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29
Q

What can you infer if you see 2 embryos, with 1 yolk sac on US?

A
  • MONOchorionic-MONOamniotic
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30
Q

What is considered advanced maternal age?

A

age 33= increased risk of fetal aneuploidy (down syndrome).

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31
Q

Is the likelihood of having a baby with down syndrome in a trichorionic-triamniotic pregnancy the same parental age as a parent with a singleton pregnancy?

A

NO, age drops to 28

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32
Q

What is used more now instead of amniocentisis?

A
  • analyze the fetal DNA in the maternal serum :)
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33
Q

What is the management of dichorionic-diamniotic twins?

A
  • US every 4-6 weeks
  • serial nonstress testing during 3rd trimester (weekly)
  • deliver by 38 weeks
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34
Q

What is twin-to-twin transfusion syndrome (TTTS)?

A
  • abnormal blood vessel connections in the placenta allow blood to flow unevenly between the babies; occurs in MONOchorionic-diamniotic twins
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35
Q

If one baby dies in a MONOchorionic-diamniotic or MONOchorionic-MONOamniotic, is there a risk of neurologic impairment (cerebral palsy) of the surviving twin?

A

YES

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36
Q

What is the management of MONOchorionic-diamniotic twins?

A
  • US every 2 weeks to rule out TTTS.
  • US every 4 weeks to evaluate interval fetal twin growth.
  • serial nonstress testing during 3rd trimester
  • deliver by 34-36 weeks
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37
Q

What is the management of MONOchorinoic-MONOamniotic twins?

A
  • US every 2-3 weeks
  • come in daily for 4 hours for fetal non-stress monitoring.
  • deliver at 32 weeks via cesarean section (give MgSO4 and dexamethasone to reduce complications).
38
Q

What is the most common variety of conjoined twins?

A
  • thoracopagus, followed by omphalopagus
39
Q

Do most conjoined twins spontaneously miscarry?

A

YES

40
Q

What are the complications of an incompatible blood transfusion?

A
  • hemolysis
  • renal failure
  • shock
  • death
41
Q

What is the most common blood type?

A

O+

42
Q

** What is the INDIRECT antiglobulin test (IAT)? (TEST QUESTION)

A
  • maternal antenatal antibody screen

* aka how a pregnant mom is evaluated to determine whether or not she has antibodies to her RBCs or Rh

43
Q

What happens if a mother is Rh- and the fetus is Rh+?

A

if the RBCs cross the placenta, the antibodies can attack the Rh+ RBCs of the fetus causing hemolysis, anemia, heart failure, and even death of the fetus.

44
Q

What is Rh sensitization?

A
  • in the first pregnancy of an Rh- mom with an Rh+ dad, the mom is exposed to the Rh + factor of the baby for the first time during delivery, causing her to develop antibodies to this Rh factor antigen. First baby is fine.
  • in the second pregnancy of an Rh+ baby, the mother’s IgG antibodies will cross the placenta and attack the fetal RBCs causing erythroblastosis fetalis (rhesus sensitization).
45
Q

In what does erythroblastosis result?

A
  • hemolysis
  • hyperbilirubinemia (due to lysis of RBCs= bilirubin).
  • fetal anemia
  • high output heart failure
  • pallor
  • hepatosplenomegaly
46
Q

** What is RHOGAM (Anti-Rh(D) immunoglobulin)?

A
  • medication that prevents the maternal immune system from recognizing fetal Rh+ RBCs.
  • give at 28 weeks gestation to Rh- moms and then again (within 72 hours) to mother after delivery if baby is Rh+.
47
Q

When does Rh sensitization occur?

A
  • delivery (vaginal or cesarean section).
  • prenantal diagnosis (CVS or amniocentesis).
  • blunt trauma to gravid abdomen (ex. car accident).
  • antenatal hemorrhage
  • ectopic pregnancy
  • vaginal bleeding
48
Q

What is the first thing we do at a mother’s first prenatal appointment?

A
  • ABO blood type and INDIRECT Coombs (IAT) antibody screen.

- If Rh- and no evidence of sensitization, then she is managed as a routine pregnancy.

49
Q

Do we give RHOGAM if mother is already sensitized?

A

NO, because this is just to prevent sensitization.

50
Q

In the event of a fetal-maternal hemorrhage, will one dose of RHOGAM (anti-Rh(D) immunoglobulin) prevent Rh sensitization?

A

YES :)

51
Q

What will the Rosette test tell you after delivery?

A
  • tests for significant amount of fetal-maternal hemorrhage (more than 30 cc’s).
52
Q

What must you also do if Rosette test is +?

A

perform Kleihauer-Betke stain= tells you how much fetal blood is in the maternal circulation

53
Q

What do we do if the mom is already Rh sensitized?

A
  • titrate the amount of Rh antibodies in her serum (ex. 1:1 not bad, but 1:56 is bad).
54
Q

What is the critical Rh titer?

A
  • the level at which the mother is significantly sensitized that she may be producing enough antibodies to cause fetal anemia from fetal hemolysis.
  • 1:16 is typical critical level
55
Q

What must we do once the critical Rh(D) antibody level is reached?

A
  • determine father’s (paternal) zygosity.
  • if he’s heterozygous, then perform amniocentesis to evaluate fetal Rh(D).
  • if he’s homozygous, then fetus is at risk
56
Q

What happens as a result of fetal anemia do to Rh sensitization of the mother?

A
  • blood viscosity increases, causing the heart to pump harder (increasing CO and velocity).
57
Q

How do we evaluate blood viscosity?

A
  • US color doppler of middle cerebral artery to calculate peak systolic velocity.
58
Q

How many vessels are in an umbilical cord?

A

2 arteries and 1 vein usually.

59
Q

** What do we do if the fetus is anemic?

A
  • intrauterine vascular TRANSFUSION of 80% packed RBCs
60
Q

Are there other minor RBC antigens and antibodies?

A

YES. If mom has any of these, we follow her the same way we would follow Rh disease= titer testing every 4 weeks until 24 weeks, and then every 2 weeks thereafter (or until she hits the critical threshold).

61
Q

Is there any medication to prevent anemia from a minor RBC antigen?

A

NO, only for Rh disease.

62
Q

What is fetal/neonatal alloimmune thrombocytopenia?

A
  • mom has antibody against a platelet antigen that the father has given to the fetus. The fetus can spontaneously bleed and die.
63
Q

** How do you manage minor RBC antigen problems? (TEST QUESTION)

A
  • you can do in vitro fertilization by transferring only those embryos that don’t have the minor antigen (only if father is HETEROZYGOUS).
  • if HOMOZYGOUS, then you can use a gestational carrier, but make sure the mom carrying the baby doesn’t have antibody against the minor antigen.
64
Q

What is the average fetal (embryonic age) age?

A
  • 38 weeks (266 days)
65
Q

What is Naegle’s rule for assessment of gestational age?

A

FDLMP - 3 months + 7 days= due date

66
Q

What can you do after 20 weeks of pregnancy to evaluate fetal size?

A
  • measure the maternal abdomen (FUNDAL HEIGHT in cm from the pubic symphysis correspond to number of weeks pregnant).
    Ex. 28 cm = 28 weeks pregnant.
67
Q

What is Leopold’s maneuver?

A
  • way to assess the size of the baby and fetal presentation.
  • not very accurate
68
Q

How does US in OB compare to other US modalities?

A
  • 2-12 million cycles/sec compared to normal US of 20,000 cycles/sec
69
Q

How does US work?

A
  • by applying an electrical potential to Piezoelectric crystals in the US transducer (probe) that causes crystals to mechanically deform, and this deformation results in formation of an acoustic wave.
  • each piezoelectric crystal functions as both a transmitter and receiver of mechanical energy.
  • the piezoelectric crystal waits to receive the returning echoes, which it converts back to electrical energy.
  • display of these returning electrical signals (echoes) creates images.
70
Q

*** How does frequency of US compare to wavelength?

A

the higher the frequency the shorter the wavelength, and the greater the image resolution (but lower penetration).
*OB uses 2-12 MHz

71
Q

Does oligohydramnios make US easier or harder?

A
  • harder, because US waves go more easily through fluids, an oligohydramnios has little fluid around the fetus.
72
Q

What is the timetable for US visible structures in a developing fetus?

A
  • 4.5-5 weeks= gestational sac.
  • 5 weeks= yolk sac within that sac.
  • 5.5-6 weeks= cardiac activity and embryo (measurable crown rump length).
73
Q

When do you change the “due date” based on US discrepancy with FDLMP?

A
  • if less than 9 weeks, must have 5 days or more difference in US date.
  • if 9-14 weeks, must have 8 days or more difference.
74
Q

What is the most accurate measure for dating by US?

A
  • crown rump length measurement (CRL)
75
Q

** What do we use to estimate fetal size and date when baby is at 14-22 weeks gestational age?

A
  1. HEAD CIRCUMFERENCE (most predictive US parameter at this point).
  2. biparietal diameter
  3. abdominal circumference
  4. femur length
76
Q

** What US measurement is best for evaluating gestational age in the third trimester?

A

FEMUR LENGTH

77
Q

What is fetal macrosomia?

A
  • large fetus (4500 grams) and morbidity significantly increases.
78
Q

** What are the major complications of fetal macrosomia? (TEST QUESTION)

A
  • shoulder dystocia= the anterior shoulder of the infant cannot pass the pubic symphysis, leading to brachial “Erb-Duchenne” palsy.
  • neonatal hypoglycemia
  • metabolic syndrome
  • impaired glucose tolerance and obesity.
79
Q

What is the amount of time that you should delivery a baby after the head is out?

A
  • 5 mins max
80
Q

** What are the risk factors for fetal macrosomia?

A
  • DM (because the placenta makes hormones that make her carbohydrate intolerant, leading to the fetus’s response of increased insulin production, which acts as a growth factor).
  • prior Hx of fetal macrosomia
  • weight gain prior to or during pregnancy
  • multiparity (babies tend to get larger for subsequent pregnancies).
  • male
  • ethnicity
  • gestation greater than 40 weeks.
  • positive 1 hr glucose tolerance test (GTT) with normal 3 hour GTT.
81
Q

What are the maternal risks of fetal macrosomia?

A
  • protracted/arrested labor
  • operative vaginal delivery (forceps for vacuum assisted).
  • Cesarean delivery
  • genital tract lacerations
  • postpartum hemorrhage
82
Q

** How do you manage fetal macrosomina? (TEST QUESTION)

A
  • AVOID operative vaginal delivery (FORCEPS, VACUUM)
  • consider elective CESAREAN SECTION if over 5,000 grams or 4,500 (with DM).
  • consider cesarean section for fetuses with small head circumference/abdominal circumference (HC/AC ratio).
83
Q

What is fetal growth restriction?

A

small baby (less than 10th percentile).

84
Q

What does growth velocity (fetal abdominal growth of less than 10 mm over 2 weeks) reflect?

A
  • decreased abdominal adipose tissue and decreased hepatic size related to decreased glycogen storage in the liver.
85
Q

Does perinatal mortality go up as birth weight goes down?

A

YES

86
Q

Why do we look at the fluid when a fetus is not growing well?

A
  • amniotic fluid is fetal urine. If the baby is not being appropriately oxygenated, the kidneys are not being adequately perfused, and are therefore making less urine (amniotic fluid)= BAD.
87
Q

What happens when the placenta is not functioning well?

A
  • it becomes progressively more difficult for the baby to get blood flow back to the placenta so that it can be adequately re-oxygenated.
  • do a doppler eval of the umbilical artery to see how difficult it is (resistance of blood flow) for the baby to get blood flow back to the placenta.
88
Q

Are most babies under the 10th weight percentile normal?

A

YES, but 20% are pathologic.

89
Q

Of the 20% of pathologic cases of babies under the 10th weight percentile, what are the causes?

A
  • 75%= extrinsic (placental)

- 25%= intrinsic (chromosomal, infection, anomaly).

90
Q

Is there less vascularization of the maternal bed to the placenta in fetal growth restriction or pre-eclampsia?

A

YES

91
Q

** What happens if the fetus is not getting adequate oxygenation due to fetal growth restriction?

A

it shunts blood flow to the brain, causing increased end diastolic velocity. This can be evaluated with doppler of the middle cerebral artery!

RGU 2 (24 decks)

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