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Obstetrics and Gynaecology > Preconception and Prenatal Care > Flashcards

Preconception and Prenatal Care Flashcards

1
Q

Define gestation

A

From first day of last menstrual period, assumes conception two weeks beyond this date

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2
Q

What is Naegle’s rule?

A

Used to assess approximate due date

First day of LMP + 9/12 +1/52 on 28 day cyle

OR

First day of LMP + 1/52 - 3/12

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3
Q

What are the main things that need to be covered during preconception counselling (3)?

A
  1. Past medical history - optimise medical illnesses and necessary medications prior to pregnancy
  2. Supplementation - folic acid; start 3 months preconception until end of T1 to prevent NTDs; iron supplementation and previtamins
  3. Risk modification - lifestyle, medications (teratogenic?), infection screening, genetic testing as appropriate for high risk groups, social
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4
Q

What investigations are usually done in the initial prenatal visit? (3)

A
  1. Bloodwork - FBE, blood group and type, Rh antibodies, infection screening (rubella, varicella, syphilis, Hep B,C , HIV)
  2. MSU - bacteriuria/proteinuria
  3. Pelvic exam - Pap smear (unless done within last 6-12 months)
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5
Q

How often should prenatal visits occur?

A

For uncomplicated pregnancies:

until 28 weeks - q4-6weeks
from 28-36 weeks - q2-3 weeks
from 36 weeks until delivery - weekly

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6
Q

What needs to be assessed at every prenatal visit? (4)

A
  1. Record estimated GA
  2. History of present pregnancy: foetal movements,uterine bleeding,cramping
  3. Physical exam: BP, weight gain, symphysis fundal height (SFH), Leopold’s maneouvres (T3) for lie, position and presentation of foetus
  4. Investigations: urinalysis for glucosuria, ketones, proteinuria, foetal heart tones starting at 12 weeks using doppler, liquor volume
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7
Q

What needs to be assessed during a physical exam at prenatal visits? (4)

A
  1. BP
  2. Weight gain
  3. Symphysis fundal height (SFH)
  4. Leopold’s maneouvres (T3) for lie, position and presentation of foetus
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8
Q

What is the expected SFH at 12 weeks?

A

uterine fundus at pubic symphysis

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9
Q

What is the expected SFH at 20 weeks?

A

Fundus at umbilicus SFH should be within 2 cm of GA between 20-36 weeks

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10
Q

What is the expected SFH at 37 weeks?

A

Fundus at sternum

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11
Q

WHen are Leopold’s Maneouvres performed?

A

T3 - after 30-32 weeks gestation

But remember! US required to conclusively determine position

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12
Q

What are the four Leopold’s maneouvres?

A
  1. To determine which foetal part is lying furthest away from the pelvic inlet
  2. TO determine the location of the foetal back
  3. Pawlick’s Grip - to determine which foetal part is lying above the pelvic inlet
  4. To locate the foetal brow
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13
Q

Name 4 causes of a foetus being small for dates

A
  1. Date miscalculation
  2. IUGR
  3. Foetal demise
  4. Oligohydramnios
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14
Q

Name 3 causes of a foetus being large for dates

A
  1. Date miscalculation
  2. Multiple gestation
  3. Polyhydramnios
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15
Q

What is the accuracy of using US in establishing GA in the first trimester vs second trimester?

A

First trimester = adequately accurate (+/- 7 days)

18-20 weeks = accuracy +/- 10days-2 weeks

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16
Q

At which points is U/S used in prenatal screening? (3)

A
  1. Dating (8-12 weeks) - remember, dating more accurate in T1 than in T2 when using US
  2. Nuchal translucency (11-14 weeks)
  3. Dates, foetal growth and anatomy assessment (18-20 weeks)

But earlier or subsequent US performed when medically indicated

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17
Q

What is the Combined Test, when is it conducted and what three measures are looked at?

A

Combination of US and blood test to screen for risk of Down Syndrome. Trimester 1

  1. Nuchal translucency on US (between 11 and 13 weeks, ideally 12)
  2. beta-HCG
  3. PAPP-A (pregnancy-associated plasma protein A)

Blood tests measured between 9 and 13 weeks, ideally 10th week)

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18
Q

What is the second trimester serum screen, when is it conducted, and what 4 measures are looked at?

A

Screens for Down syndrome, Trisomy 18 and NTDs

14 - 20 weeks (ideally between 15 and 17)

  1. MSAFP (maternal serum alpha feto-protein)
  2. beta-HCG
  3. Unconjugated oestrogen (oestriol)
  4. Inhibin A
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19
Q

What is chorionic villus sampling and when is it conducted?

A

Biopsy of chorion using a trans-abdominal needle or trans-cervial catheter at 10-12 weeks

20
Q

List three advantages of chorionic villus sampling.

A
  1. Enables pregnancy to be terminated earlier than with amniocentesis
  2. Rapid karyotyping (takes 2 weeks) and biochemical assay within 48h, including FISH analysis
  3. High sensitivity and specificity
21
Q

List 2 disadvantages of chorionic villus sampling.

A
  1. 1-2% risk of spontaneous abortion and risk of foetal limb injury
  2. Does not screen for open neural tube defects
22
Q

What is amniocentesis, and when is it conducted?

A

US-guided transabdominal extraction of amniotic fluid, done at 15-20 weeks gestation

23
Q

List three advantages of amniocentesis

A
  1. Also screens for open neural tube defects (acetylcholinesterase and amniotic AFP)
  2. In women > 35 yrs, the risk of chromosomal anomaly (1/180) is greater than the risk of miscarriage from the procedure
  3. More accurate genetic testing than CVS
24
Q

List two disadvantages of amniocentesis

A
  1. 0.5% risk of spontaneous abortion and risk of foetal limb injury
  2. Results take 14-28d
25
Q

What is isoimmunisation?

A

Isoimmunisation - when antibodies are produced against a specific RBC antigen as a result of antigenic stimulation with RBC of another individual

26
Q

What are the different ways in which isoimmunisation in pregnancy can occur? (5)

A
  1. Incompatible blood transfusions
  2. Previous foetal-maternal transplacental haemorrhage e.g. ectopic pregnancy
  3. Invasive procedures in pregnancy - e.g. CVS, amniocentesis
  4. Any type of abortion
  5. Labour and delivery
27
Q

How is Rh status and antibodies measured in isoimmunisation screening?

A

Usually done at first prenatal visit - measured by indirect Coombs test

28
Q

What are the two stages of the indirect Coombs test?

A
  1. Washed RBCs incubated with test serum. If serum contains antibodies to antigens on RBC surface, antibodies will bind
  2. RBCs washed with isotonic saline and then incubated with Coombs reagent (antihuman globulin). If antibodies have bound to RBC surface antigens in first stage = agglutination = POSITIVE
29
Q

How is the severity of foetal anemia assessed if Rh positive and antibodies are present? Benign vs cause for concern?

A

Antibody concentration (via indirect COOMBS TEST??)

(sometimes 1:32 used, different values at different labs)

Ab titres less than 1:16 - benign
Ab titres equal to or greater than 1:16 - necessitates amniocentesis to determine severity of foetal anaemia (correlates with the amount of biliary pigment in amniotic fluid from 27 wks onward)

30
Q

What is the Kleihauer-Betke test? How is it conducted?

A

Used to determine extent of foetomaternal haemorrhage i.e. used to measure the amount of fetal hemoglobin transferred from a fetus to a mother’s bloodstream.

Standard blood smear prepared from mother’s blood, exposed to acid bath

Adult Hb from RBCs removed, foetal RBCs identified with subsequent staining (rose pink). Adult RBCs “ghost cells”

Calculation performed - not very precise i.e. cannot detect very small amounts

31
Q

How does Rh IgG/anti-D work?

A

Binds to Rh antigens of foetal cells and prevents them from contacting maternal immune system

32
Q

When is Rh IgG/anti-D given to Rh negative women? (7)

A
  1. Routinely at 28 weeks GA (provides protection for ~12 weeks)
  2. Within 72 h of the birth of an Rh positive foetus
  3. With a positive Kleihauer-Betke test
  4. With any invasive procedure (amniocentesis, CVS)
  5. In ectopic pregnancy
  6. With miscarriage or therapeutic abortion
  7. With an antepartum haemorrhage
33
Q

What should be done if a mother is Rh negative and Ab screen positive?

A

No benefit from Rh IgG

Follow mother with serial monthly Ab titres throughout pregnancy +/- serial amniocentesis as needed

34
Q

How should a foetus with haemolytic anaemia be managed? (2)

A
  1. If falling biliary pigment on serial amniocentesis - no intervention (usually indicative of either unaffected or mildly affected foetus)
  2. Intrauterine transfusion of O-negative pRBCs may be required for severely affected foetus, or early delivery of foetus for exchange transfusion
35
Q

How is foetal anaemia investigated? (4)

A
  1. Ultrasound: MCA doppler, AFI, UA doppler, evidence of hydrops
  2. Antibody titre
  3. Amniocentesis if anitbody titres high
  4. Cordocentesis in rare instances
36
Q

What i the risk of having a baby with Down syndrome in the following ages?
25
35
40

A

25 - 1 in 1350
35 - 1 in 355
40 - 1 in 90

37
Q

What are the clinical risk factors for infants developing early onset disease GBS infection? (6)

A
  1. Gestation less than 37 weeks
  2. Prolonged rupture of membranes
  3. Maternal fever
  4. Previous GBS infected baby
  5. GBS bacteriuria
  6. Positive GBS in current pregnancy
38
Q

How is GBS screened for?

A

Combined low vaginal and anorectal swab a 35-37 weeks gestation - screening cultures take 24-48h

39
Q

What is involved in GBS prophylaxis?

A

Penicillin given approx. 4 hours to delivery

40
Q

List 6 soft markers of aneuploidy seen on US

A
  1. Nuchal fold thickness
  2. Ventriculomegaly
  3. Absent nasal bone
  4. Echogenic intracardiac focus
  5. Echogenic bowel
  6. Choroid plexus cyst
41
Q

Which vaccines are safe to give in pregnancy? (4)

A

Diphtheria, influenza, hep B, tetanus

42
Q

Which vaccinations are contraindicated in pregnancy? (2)

A

Rubella, oral typhoid

43
Q

What is the most accurate way of determining GA?

A

12 week US looking at crown-rump length

44
Q

When is a morphology scan usually conducted?

A

18-20 weeks

45
Q

Which 4 parameters are looked at in a biophysical profile?

A
  1. Amniotic fluid volume - fluid pocket of 2cm in 2 axes
  2. Breathing -
  3. limb movement
  4. foetal tone - at least one episode of limb extension followed by flexion

Obstetrics and Gynaecology (10 decks)

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