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GH Coarsework 2023 > Prenatal And Preimplantation Genetics > Flashcards

Prenatal And Preimplantation Genetics Flashcards

1
Q

Causes of male infertility

A
  1. Abnormal sperm production or function
  2. Problem with the delivery of sperm
  3. Overexposure to certain environmental factors
  4. Damage related to cancer and its treatment
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2
Q

Causes of female infertility

A
  1. Ovulation disorders
  2. Uterine or cervical abnormalities
  3. Fallopian tube damage or blockage
  4. Endometriosis
  5. Polycystic ovarian syndrome
  6. Primary ovarian insufficiency
  7. Pelvic adhesions
  8. Cancer and its treatment
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3
Q

Risk factors for infertility in males and females

A
  1. Age
  2. Tobacco use
  3. Alcohol use
  4. Being overweight
  5. Being underweight
  6. Exercise issue
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4
Q

Types of assisted reproductive technology

A
  1. Ovulation induction
  2. In vitro fertilisation (IVF)
  3. Intrauterine insemination (IUI)
  4. Intrafallopian transfer
  5. Intracytoplasmic sperm injection
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5
Q

Characterise ovulation induction

A

Ovulation induction is a treatment that uses hormone therapy to induce or help regulate ovulation in women trying to fall pregnant. Problems ovulating is one of the most common cause of infertility in women. Ovulation induction paired with timed intercourse is therefore often the first step in the management of infertility.

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6
Q

Characterise in vitro fertilisation (IVF)

A
  1. During an IVF cycle, a FS retrieves egged from the woman and then fertilised them with sperm. The fertilised egg grows in a Petri dish for several days until it becomes an embryo. FS implants the embryo back into the woman uterus.
  2. To maximise the success odds of IVF treatment, a woman usually takes fertility drugs to ensure she ovulates on a predictable timeline and to encourage her body to produce multiple extra eggs.
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7
Q

Indications for PGT-M testing

A
  1. Autosomal recessive conditions in which both parents are known genetic carriers, such as cystic fibrosis.
  2. Autosomal dominant conditions in one or both parents, such as Huntington’s disease.
  3. X-linked disease, such as haemophilia
  4. Sex-selection for X-linked conditions
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8
Q

Indications of PGT-SR testing

A
  1. Balanced reciprocal translocation carrier parent
  2. Robertsonian translocation carrier parent
  3. Inversion carrier
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9
Q

Indications for PGTA testing

A
  1. Advanced maternal age
  2. Recurrent pregnancy loss
  3. Male infertility
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10
Q

Advantage of PGT

A
  1. Biologically related, unaffected child
  2. Avoidance of termination of pregnancy
  3. Avoidance of recurrent miscarriage
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11
Q

Characterise Intrauterine insemination

A
  1. Intrauterine insemination is a fertility treatment where sperm are placed directly into a woman uterus
  2. With IUI, sperm are washed and concentrated, and also placed directly into the uterus, which puts them closer to the egg.
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12
Q

Intrauterine insemination is useful when ?

A
  1. For women trying to get pregnant without a partner/ frozen sperm
  2. For people with unexplained infertility
  3. When the mans sperm has issues travelling to the egg —often due to low mobility, but sometimes due to a chemical mismatch between the mans semen and the woman’s vaginal fluids.
  4. Endometriosis, irregular menstruation cycles and anovulation
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13
Q

Characterise Intrafallopian transfer

A
  1. Intrafallopian transfer uses multiple eggs collected from the ovaries. The eggs are placed into a thin flexible tube along with the sperm to be use.
  2. The gametes are then injected into the Fallopian tubes using a surgical procedure called laparoscopy
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14
Q

Intrafallopian transfer are good options for couples

A
  1. With unexplained infertility
  2. With sperm mobility issues
  3. When the woman has an issue with her Fallopian tube, such as a blocked tube
  4. Couples who believe fertilisation needs to occur in the body.
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15
Q

Characterise Intracytoplasmic sperm injection

A
  1. ICSI is a procedure in which sperm are directly injected into the egg.
  2. Using microscope, a single sperm is injected into the centre of a mature egg using a very fine glass needle.
  3. The early stages of ICSI treatment are the same as for conventional IVF .
  4. Each egg is injected with a sperm cell such that several embryos will be available for transfer and storage.
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16
Q

Intracytoplasmic sperm injection works best when?

A

When there are serious issues with sperm such as:
1. Low sperm motility, few quality sperm or abnormally shaped sperm.
2. DNA damage

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17
Q

Risk associated with ART

A
  1. Multi feral gestation
  2. Prematurity,
  3. Low birth weight
  4. Small for gestation age
  5. Perinatal mortality,
  6. Caesarean delivery
  7. Placenta previa
  8. Placental abruption
  9. Preeclampsia
  10. Birth defects
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18
Q

Explain fetal reduction

A

Termination of one or more foetuses to a lower fetal number decreases the risk of preterm delivery, although the decrease should be balanced against a procedure-associated risk of miscarriage.

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19
Q

Talk about birth defects caused by ART

A
  1. Studies have documented small increases in birth defects among infants of women who became pregnant through ART
  2. Any elevated risk of birth defects associated with ART could be due to manipulation of the oocyte and embryo that are necessary with ART procedures or to factors related to the stimulation.
  3. However, risk also may be related to the underlying cause of infertility or other specific health risks and behaviours in those undergoing ART.
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20
Q

Differentiate between prenatal screening and diagnosis.

A

1.1 Prenatal screening is the process of separating high risk pregnancies from low/population risk pregnancies, results do not confirm a diagnosis.
1.2 but prenatal diagnosis investigates a foetus during pregnancy to confirm a definite diagnosis

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21
Q

Purpose prenatal screening

A

It is used to give indication if pregnancy at higher risk than average, and if further diagnostic testing should be considered/ offered.

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22
Q

Types of prenatal screening

A
  1. History taking and obstetric examinations
  2. Fetal ultrasound
  3. Biochemical testing
  4. Non-invasive prenatal testing (NIPT)
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23
Q

Why is there a need for non-invasive test

A

Noninvasive testing grew out of a desire to avoid direct contact with the growing fetus/ placenta and risking the health of the fetus.

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24
Q

Why is cell-free fetal DNA is better than fetal cells in maternal circulation

A
  1. It is estimated that after the first trimester, there is approximately one fetal cell in the maternal circulation for every 10000 to 1 million maternal cells.
  2. To isolate and purify these fetal cells for subsequent analysis have been largely unsuccessful due to the scarcity of fetal cells in maternal blood.
  3. For this reason, the focus has shifted to the analysis of cell-free fetal DNA, which is found at a concentration almost 25 times higher than that available from nucleated blood cells extracted from a similar volume of whole maternal blood.
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25
Q

What percentage of the maternal cfDNA is cf-fetal DNA

A

3% to 10% of the cfDNA in the maternal circulation comes from the fetoplacental unit.

26
Q

Characterise cell free fetal DNA

A
  1. CfDNA in the blood is caused by breakdown of placental cells that is taken up into the mothers blood stream.
  2. Fetal DNA comprises comprises only a small portion of total cell free DNA -close to 10-20% in the last weeks of gestation.
  3. The fetal DNA detection time spans from 4 to 5 weeks of gestation until delivery.
  4. Therefore eliminating the risk of it persisting into the next pregnancy, which would cause confounding effects.
  5. The proportion of cffDNA grows by 0.1% every 7 days between the 10th and 21st gestational week: after the 21st week this increase is faster, with a weakly 1% increase.
27
Q

The amount of circulating fetal DNA depends, in addition to the gestation period and the progression of the pregnancy, on other factors such as :

A
  1. Presence of maternal diseases
  2. Body weight
  3. Aneuplodies
  4. Twin pregnancies
28
Q

Define fetal fraction

A

The proportion (must be above 4%) of cfDNA in maternal blood that comes from the placenta

29
Q

How is NIPT performed

A
  1. During pregnancy, the mother bloodstream contains a mixture of cfDNA that comes from her cells and cells from the placenta.
  2. These cells are shed into the mothers bloodstream throughout pregnancy.
    3.. The DNA in placental cells is usually identical to the DNA of the fetus.
    4, analysing cfDNA from the placenta provides an opportunity for early detection of certain genetic abnormalities without harming the fetus
30
Q

NIPT can detect the following:

A
  1. Trisomy 21
  2. Trisomy 18
  3. Trisomy 13
  4. Triploidy
  5. Monosomy X (a little bit iffy with the sex chromosomes)
  6. Microdeletions
  7. Gender
31
Q

Who needs to consider NIPT

A

NIPT is usually offered to pregnant women identified by their doctor to have a increased chance of a fetus with an aneuploidy at typically done 11 to 14 weeks gestation.

32
Q

Who is classified as intermediate, high risk and is offered NIPT.

A
  1. Maternal age >35 years of age
  2. Positive family history of aneuploidy
  3. Parent who carries a relevant roberstonian translocation.
33
Q

Different applications for non-invasive prenatal testing

A
  1. Fetal gender determination
  2. Fetal RhD genotyping
  3. Detection of aneuplodies
  4. Twin zygosity
34
Q

How to distinguish fetal vs maternal DNA

A
  1. Genotyping difference
  2. Counting (looking for copy number variation)
  3. Epigenetic differences
35
Q

How is counting done to distinguish fetal vs maternal DNA

A

There is always more maternal cfDNA than fetal DNA. But if an aneuploidy exists in the fetus - for that chromosome, the fetus will have a different proportionate amount of cfDNA as compared to the other fetal chromosome

36
Q

How is NIPT outcome concentration affected by the type of trisomy.

A
  1. The fetal DNA concentration decreases when the fetus has trisomy 13 or 18 which might be due to a smaller placental size and IUGR observed in trisomy 13 and 18.
  2. There is some evidence that the fetal DNA concentration increases in the case of trisomy 21 which may be due to higher FF (Fetal fluid)
37
Q

The most common reason for non-reportable results include;

A
  1. Insufficient absolute amount of total and/ or fetal/ placental DNA
  2. Fetal fraction (FF) below an acceptable level
  3. Insufficient numbers of fragments sequenced and /or aligned.
38
Q

Pros of NIPT

A
  1. Non-invasive prenatal testing offers an intermediate step between serum screening and invasive diagnostic testing.
  2. NIPT is most accurate screening test and produces fewer false positives.
  3. The only physical risk associated with the procedure are those normally associated with a blood draw and there is no risk of miscarriage.
39
Q

What is the point of prenatal investigations

A
  1. To assess development of a fetus
  2. To detect any abnormalities in the development of fetus.
  3. To offer option of terminating pregnancy in case of a or outcome.
40
Q

Pregnant Woman off all ages need prenatal testing if?

A
  1. There is a close relative/previous child with a serious genetic condition.
  2. One of the partners of a couple has a serious condition that may be passed on to a baby.
  3. One or both parents are known carriers or are affected with a genetic disorder.
  4. There has been some teratogenic exposure during the pregnancy.
  5. There has been a positive screening test indicating an increased risk of an abnormality
41
Q

Utilisation of fetal ultrasound

A
  1. Determine existence and gestational age of pregnancy
  2. Determine size of fetus
  3. Examine growth and development
  4. Detect structural features
  5. Recognise and detect some fetal abnormalities, malformations.
42
Q

What do the increased measurement of the nuchal translucency mean.

A

Increased measurement = risk of chromosome, skeletal, cardiac abnormalities.

43
Q

What do the 11-14week and 20 week ultrasound look for ?

A

11-14week: thickness of fluid -filled space behind neck
20 weeks : baby’s bones, heart, brain, spinal cord, face, kidney and abdomen

44
Q

Soft markers

A

Fetal sonogaphic findings that are generally not abnormalities as such but are indicative of an increased age adjusted risk of an underlying fetal aneuploidic or some non-chromosomal abnormalities.

45
Q

What does the First trimester (11 to14weeks ) biochemical screening look for ?

A
  1. Blood test measures levels of specific proteins in mother blood.
  2. This is done conjunction with 12 week sonar -> detects 90% of babies with DS
46
Q

Goals of dong prenatal diagnosis

A
  1. Manage risk
  2. Enable couples to have healthy children
  3. Plan prenatal or postnatal treatment
  4. Psychological preparation
47
Q

What sample is taken during chronic villus sampling (CVS)

A
  1. Sample is retrieved from the placenta which contains the same material as fetus which originates from the same embryonic tissues.
48
Q

When is chronic villus sampling done

A

11 and 14 weeks gestation

49
Q

Pros of chronic villus sampling

A
  1. Earlier results which allows for easier termination of pregnancy
50
Q

Cons of chronic villus sampling

A

Invasive procedure;
1. Miscarriage risk
2. Risk of infection
3. Risk of bleeding/ cramping
4. Risk of MTCT
5. Evidence for limb defects < 9 weeks
6. Maternal contamination

51
Q

What sample is taken during amniocentesis

A
  1. Sample of amniotic fluid, which contains fetal skin/ fibroblast cells.
52
Q

When is amniocentesis performed

A

16-22 weeks

53
Q

Pros of amniocentesis

A
  1. Miscarriage risk
  2. Less risk of sample failure than CVS
54
Q

Cons of amniocentesis

A
  1. Invasive procedure
  2. Miscarriage risk
  3. Infection risk
  4. Risk of mother to child transmission
  5. Later stage- psychosocial issues
  6. TOP more complex
55
Q

What sample is taken in cordocentesis

A

Fetal blood collected from umbilical cord which contains white blood cells

56
Q

When is cordocentesis performed

A

18 weeks gestation

57
Q

Pros of cordocentesis

A
  1. Offer if patient has booked in too late for earlier testing, and abnormalities have been noted
  2. Convenient sample for analysis
58
Q

Cons of cordocentesis

A
  1. Invasive procedure
  2. Miscarriage risk
  3. Infection risk
  4. Fetus older-psychosocial issues
  5. TOP more complex
  6. Risk of mother to child transaction
59
Q

Termination of pregnancy at 12 weeks

A
  1. Upon request
  2. consultation with medical professional not required
  3. Permission from parental guardians not required for minors
60
Q

Termination of pregnancy act at 13-20

A
  1. Requires consultation with medical practitioner/ midwife
  2. Risk to mother mental/ physical health
  3. Risk to foetus because of severe physical/mental abnormalities.
  4. Significant effect on social/ economic circumstances
61
Q

Termination of pregnancy act 20 weeks

A
  1. Requires consultation with medical practitioner/midwife.
  2. Mothers life endangered
  3. Severe malformation of fetus
  4. Poses risk of injury to fetus.

GH Coarsework 2023 (13 decks)

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