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O&G > Amniocentesis and chorionic villus sampling > Flashcards

Amniocentesis and chorionic villus sampling Flashcards

1
Q

What is the combined test for Down’s syndrome?

A
  • Done at 11-13+6 weeks
  • Nuchal translucency + serum Beta-hCG + serum pregnancy-associated plasma protein A (PAPP-A)
  • Down’s syndrome more likely:
    (i) increased nuchal translucency
    (ii) high beta-hCG
    (iii) low PAPP-A
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2
Q

What is the quadruple screening test?

A
  • Done if late to antenatal screening (15-20 weeks)
  • AFP + unconjugated oestriol, beta-hCG, inhibin A
  • triple test does not include inhibin A
  • Down’s syndrome more likely:
    (i) AFP - Low
    (ii) Unconjugated oestriol - Low
    (iii) beta-hCG - High
    (iv) Inhibin A - High
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3
Q

How would you define chorionic villus sampling to a patient?

A

CVS is a procedure that is carried out during pregnancy to diagnose or exclude various chromosomal or genetic conditions
Take a sample of placental tissue to do these tests

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4
Q

Why might a woman be offered CVS during her pregnancy?

A
  • High chance of baby having Down’s syndrome
  • If they have previously had a baby with a chromosomal or genetic condition
  • If one parent has, or both have, a genetic disorder or are carriers for a genetic disorder
  • If there is a history of certain genetic conditions in the family
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5
Q

When is CVS usually offered?

A

Beginning of the 11th week and end of the 13th week

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6
Q

What screening is done before CVS is performed?

A
  • Screen for HIV and Hep B if it has not already been done
  • May also offer to screen for Hep C
  • If you have any of these infections, CVS can increase the risk of passing them onto your baby
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7
Q

How long does a CVS take to do?

A

Whole procedure takes approximately 10 min, but the appointment usually takes longer because you will need time to rest afterwards

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8
Q

Describe transabdominal CVS.

A
  • First do an USS to check the position of baby and the placenta, and to identify the best place to take a sample of placental tissue
  • Doctor will use the USS throughout to guide them during the procedure
  • May be given local anaesthetic to numb an area of skin of your tummy
  • Fine needle is then passed through your skin, into your womb, and into the placenta
  • There is a syringe attached to the end of the needle and allows a sample of tissue from the placenta to be drawn up into the syringe
  • Another USS to make sure baby is okay
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9
Q

Describe transvaginal CVS.

A
  • First do an USS to check the position of baby and the placenta, and to identify the best place to take a sample of placental tissue
  • Doctor will use the USS throughout to guide them during the procedure
  • A speculum is inserted into the vagina
  • A fine tube is then passed through the neck of your womb, into the womb so that a sample can be taken from the placenta
  • Another USS to make sure baby is okay
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10
Q

What are the benefits of CVS over amniocentesis?

A
  • Can be done earlier
  • Decision about what you would like to your pregnancy can be made sooner
  • If you decide to terminate pregnancy then can be done through a simple surgical procedure, with amniocentesis labour may need to be induced
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11
Q

What complications are associated with CVS?

A
  1. Miscarriage
    - slightly higher than amniocentesis (3 in 200)
    - because CVS is carried out earlier in pregnancy where the overall risk is higher anyways
    - most miscarriages happen within 2 weeks of CVS
  2. Infection
    - risk is <1 in 1,000 women
    - symptoms: fever, tenderness of your tummy, and contractions of your womb
  3. Rhesus disease developing in the baby
    - Rh -ve mum and Rh +ve baby
    - If you are Rh -ve you will be advised to have an injection with anti-D immunoglobulin after CVS to protect the baby
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12
Q

How should a woman expect to feel after CVS or amniocentesis?

A
  • Procedure can be a little painful, been described similar to a period pain
  • Best to arrange for someone to drive you home if possible
  • Take things easy over subsequent days
  • Light spotting of blood from the vagina can be normal immediately after CVS
  • Take paracetamol to help with the pain
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13
Q

What symptoms after CVS indicate that a woman should seek medical attention?

A
  • Severe tummy pain
  • Contractions
  • Persistent back pain
  • Continuous bleeding from your vagina
  • A watery fluid loss from your vagina
  • Smelly discharge from the vagina
  • Fever
  • Flu-like symptoms
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14
Q

How would you define amniocentesis to a patient?

A
  • Procedure that is carried out during pregnancy
  • Involves taking a sample of the amniotic fluid for testing to see if a baby has a chromosomal disorder such as Down’s syndrome
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15
Q

Why might a woman be offered amniocentesis?

A
  • If they have previously had a baby with a chromosomal, genetic condition or other disorder
  • If one parent has, or both have, a genetic disorder, or are carriers for a genetic disorder that could be passed on to the baby
  • Certain genetic conditions in the family
  • Other tests during pregnancy have raised the possibility that the baby has a chromosomal disorder such as Down’s syndrome
  • If the baby has an increased risk of a chromosomal disorder because of maternal age
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16
Q

When is amniocentesis usually offered?

A

After 15 completed weeks of pregnancy

17
Q

Why is amniocentesis generally not done before 15 weeks?

A
  • Amniotic fluid levels are too low before this
  • Increases risk of miscarriage
  • Increases risk of baby developing club foot
18
Q

What screening is done before amniocentesis is performed?

A
  • Screen for HIV and Hep B if it has not already been done
  • May also offer to screen for Hep C
  • If you have any of these infections, amniocentesis can increase the risk of passing them onto your baby
19
Q

How long does amniocentesis take?

A

Usually around 10 minutes, but appointment is usually longer because the woman needs time to rest afterwards

20
Q

Describe how amniocentesis is performed.

A
  • First do an USS to check the position of the baby and placenta
  • Doctor will use USS through as a guide during the procedure
  • Once best position is found, the skin is cleaned where the need will be inserted
  • Fine needle is pushed through your tummy and into the womb
  • A syringe is attached at the end to draw up 10-20mL of amniotic fluid
  • Amniotic fluid is replaced quickly (next time the baby pees)
  • Sometimes it is not possible to get enough fluid, usually due to the position of the baby
  • If this happens, take the needle out and try again
21
Q

What are the potential complications of amniocentesis?

A
  1. Miscarriage
    - Lower risk compared to CVS
    - Around 1 in 100 cases
    - Most likely to occur in the first 72h
  2. Infection
    - Less than 1 in 1,000 women
    - Symptoms: fever, tummy pain, womb contractions
  3. Rhesus disease in developing baby

O&G (17 decks)

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