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Obstetrics > Antenatal screening & diagnosis > Flashcards

Antenatal screening & diagnosis Flashcards

1
Q

Ultrasounds in pregnancy

A

Booking scan at 10/12 weeks
Anomaly scan at 20 weeks
Monthly antenatal appointments until 28 weeks
Fortnightly antenatal appointments until 36 weeks
Weekly antenatal appointments until term

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2
Q

Booking Scan

A

Confirm intrauterine and viable
Check for twins and chorionicity
Exclude gross structural or uterine defects
Date pregnancy

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3
Q

Anomaly Scan

A

Significant structural defects
Locate placental site
>95% sensitive for significant anomalies

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4
Q

Down’s syndrome screening

A

Combined screening 11-14 weeks
Quadruple tests 14-22 weeks
Integrated or serum integrated tests

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5
Q

Combined screening test

A

Check for hCG, PAPP-A and nuchal translucency thickness

Given to all babies in first trimester

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6
Q

Quadruple test

A

Used to test patients who present too late for the combined test –> hCG, AFP, uE3, inhibin A
This is combined with the mother’s age to approximate the risk of Down’s syndrome
At this age NT ceases to be an effective measure

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7
Q

Integrated tests

A

A two stage test which combines serum protein markers with the NT (or not if serum)
Have two sets of tests –> must blind the results. Increased reliability if there is more serum tests

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8
Q

Down’s Risks

A

Low risk is defined as less than 1/150, while more than this is high risk
If high risk then Amniocentesis or CVS is offered past 15 weeks gestation

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9
Q

CVS (Chorionic villious sampling)

A

Ultrasound guided needle is pasted into the placenta to biopsy the chorionic villi
This can be done from 11-14 weeks and carries a 1% miscarriage risk - but rapid karyotyping

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10
Q

Amniocentesis

A

an US guided needle is used to sample the amniotic fluid around the baby and this can diagnose Down’s after 15 weeks
There is a 0.5-1% risk of miscarriage

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11
Q

Nuchal translucency (NT) thickness

A

Useful as a marker for significant defects.
the thicker the greater the chance of birth defect
3.5-4.4mm 86% chance of healthy birth
>6.5mm 31% chance of healthy birth

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12
Q

First trimester booking scan

A

An USS which is mainly to date and establish the pregnancy

Have a 90% detection rate for pregnancies

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13
Q

Uterine Artery Doppler

A

Measure the resistance into uterine artery and high resistance is linked strongly to IUGR, preterm labour etc
Looking for a saw tooth pattern, absent end diastolic flow is worrying, reversed end diastolic flow is super bad

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14
Q

Parameters checked at antenatal check

A

BP and urine (for protein and glucose)
abdominal auscultation
Assess fetal size (IUGR or Macrosomia) by USS or symphysio-fundal height

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15
Q

At risk pregnancies (8)

A

Hypertension or Pre-existing medical disorders
IUGR or macrosomia
Oligohydramnios or polyhydramnios
Multiple pregnancies or Antepartum haemorrhage

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16
Q

Number of ideal antenatal appointments

A

10 for nulliparous women
7 for multiparous women
More visits correlates to worse outcomes

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17
Q

Physical examination checked at antenatal visits

5 S’s

A

Shape –> ovoid, posterior position
Size –> symphysio-fundal height
Scars –> previous surgery or CSs
Striae –> sign of previous or present pregnancy
Signs of Fetal life –> movements or heart beat

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18
Q

Antenatal haematological checks

A

Booking –> FBC (Hb and platelets)
Group and save + Rhesus status
Infection screen (Rubella, syphilis, HIV, hepatitis)
28 weeks –> repeat FBC and group and save
36 weeks –> repeat FBC and group and save

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19
Q

Free fetal DNA testing

A

Started in late 90’s –> only available commercially but useful for screening for major trisomies, sex etc
Will replace other tests eventually

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20
Q

Nuchal Fold

A

Abnormal if over 6mm –> found 0.5% of fetuses

May be of no pathological significance

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21
Q

Choroid Plexus Cysts

A

2% of fetuses at 20 weeks –> 90% resolve at 26ws
A cyst over 2mm in one or both plexuses
Can be associated with trisomy 18 or 21 but usually of no pathological significant –> number, size or complexity not important

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22
Q

Intracardiac echogenic Foci

A

Rarely inductive of Aneuploidy in women below the age of 35.

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23
Q

Hyperechogenic Bowel

A

Bowel as bright as bone –>0.2-1.4% of 2nd trimester scans Subjective
Can be due to genetic abnormalities, congential infections or Intra-uterine haemorrhage or cystic fibrosis

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24
Q

Trisomy 21

A

Down’s syndrome

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25
Q

Holoprosencephaly

A

A spectrum of cerebral abnormalities resulting from incomplete cleavage of forebrain 1 in 1000 births
30% have karyotype abnormality - trisomy 13 & 18
Can be Lobar or alobar

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26
Q

Ventriculomegaly

A

1% of pregnancies at 20 week scan
Lateral ventricle diameter of 10mm or more
Aetiology–> genetic abnormalities, congential infections or Intra-uterine haemorrhage
When extreme lead to hydrocephalus

27
Q

Dandy Walker Complex

A

Spectrum –> Loss of cerebellar vermis, cystic dilation of 4th ventricle and enlargement of cisterna magna (mega CM)
1 in 30,000 births –> Occurs in 13,18 and triploidy

28
Q

Facial Defects

A

1 in 800 births –> only indicate trisomy 13 or 18 in 1-2% of cases .
unilateral or bilateral cleft lips most common

29
Q

Congential Heart Disease

A 
5-10 in 1,000 --> heterogenous aetiology
Recognised association with trisomies:
Present in --> 80-90% of 18 or 13
--> 40-45% of trisomy 21
--> 40% of turners
30
Q

Congential Diaphragmatic Hernia

A

Herniation of abdominal viscera into the thorax
1 in 4000 births
In 50% of cases it indicates trisomy 13 or 18

31
Q

Exomphalos

A

Saculated midgut outside the body due to failure of regression of midgut from umblical stock
1 in 4000 births
Likelihood of aneuploidy decreases with gestational age –> 50% at 12ws, 30% at mid gestation, 15% in neonates –> more likely in small exomphalos containing only bowel

32
Q

Duodenal Atresia

A

1 in 5000 fetuses, –> indicates trisomy 21 in 40% of cases

Will see double bubble or polyhydramnios on USS

33
Q

Hydrops

A

The accumulation of fluid in an abnormal fetal compartment –> either immune (rhesus) or aneuploidy (10-30%) –> can be Trisomy 21 or turners

34
Q

Hydronephrosis

A

In most cases mild hydronephrosis will resolve spontaneously –> is dilated if over 4mm at 15-19wks, >5mm at 20-29wks, >7mm at 30-40wks

35
Q

Trisomy 18

A

Edward syndrome

36
Q

Trisomy 13

A

Patau syndrome

37
Q

Turner’s Syndrome (lethal type)

A

Large nuchal cystic hygromata, oedema, pleural effusions, ascities, cardiac defects

38
Q

Ultrasound signs of Trisomy 21

A

Mild ventriculomegaly Mild renal pelvis dilation
Nuchal edema shortening of limbs
Atrioventricular septal defect Echogenic bowel
Duodenal atresia Hypoplasia of mid phalanx of 5th finger (60%)

39
Q

Ultrasound signs of Trisomy 18

A

Choroid plexus cysts Facial defects
Absent corpus callosum Nucheal edema
Dandy walker complex Heart defects
Diaphragatic hernia Esophageal atresia
Exomphalos Renal defects
Myelomeningocele Growth restriction
Overlapping fingers Talipes

40
Q

Ultrasound signs of Trisomy 13

A

Holoprosencephaly Facial defects
Microcephaly Cardiac/renal defects
Exomphalos Postaxial polydactyly

41
Q

Types of CHD in trisomy 21

A

AV canal –> 45%
VSD –> 35%
Isolated ASD 8%
Isolated Tetrology of fallot–> 7%

42
Q

Turner’s syndrome (Non-lethal type)

A

Usually no USS abnormalities seen

43
Q

USS abnormalities and chromosomal defects

A

Likelihood of chromosomal abnormalities increase with number of abnormalities detected.
Offer karyotyping if single large abnormality is found for if correctable defect is noted —> many abnormalities resolve and are found in normal pregnancies

44
Q

Renal pelvic dilatation

A

Relative risk of Downs is 2, amnio is not needed in absence of other risk factors

45
Q

Diagnosis of pregnancy

A

A gestational sac can be seen from 4 1/2 weeks transvaginally and 6 weeks Transabdominally

46
Q

Gestational Sac

A

Not definate evidence of viable pregnancy - may be a delayed miscarriage (blighted ovum) - must see a fetal pole and heart beat
A pseduosac is a sign of ectopic pregnancy

47
Q

Signs of a viable pregnancy

A

Regular sac, high in the uterus with rapidly increasing bHCG

A poor prognosis –> irregular sac, poor decidual reaction and abnormal yolk sac

48
Q

Gestational age by USS

A

using a crown-rump length (CRL) - accurate to 5-7days - reliable up to 13wks
After this the spine curves and biparietal diameter should be used.

49
Q

Types of Twins

A

Dizygotic 2/3, monozygotic 1/3
2% monochorionic monoamniotic or conjointed
Lambda sign–> Dichorionic,diamniotic but ‘T’ sign–> monochorionic, diamniotic

50
Q

Complications of twins

A

monochorionic twins have a much higher mortality, TTTS, growth restriction, death of twin in utero.
should have 2-4 weekly scans to check

51
Q

Therapeutic invasive procedures (6)

A 
Intrauterine transfusion
Pleural fluid aspiration
Shunt insertion
Bladder aspiration/shunt
Amnioinfusion
fetoscopy or laser ablation
52
Q

How many antenatal appointments should a women have?

A

Nulliparous women –> 10
Multiparous women –> 7
Initial appointment with GP, booking appointment 8-12/40 and dating scan at 8-12/40, then 18-20/40 anomaly scan – subsequent appointments

53
Q

Conditions requiring additional antenatal care

A

Current Conditions –> HTN, cardiac/renal/endocrine disease, psych or autoimmune conditions, severe asthma, malignancy
Previous pregnancies –> recurrent miscarriage, preterm birth, PE or HELLP, rhesus isoimmunisaion, previous uterine surgery

54
Q

FGM in antenatal care

A

Examine for type to see if it will present an obstetric problem
Explain rules relating to performing FGM on the child

55
Q

Mental health and antenatal care

A

Should specifically ask at booking, post natally at 4-6 weeks and 3-4 months (depression or psychosis)

56
Q

Safeguarding in antenatal care

A

Make sure to be alert for the signs of abuse

Provide a sale environment so that the women feels able to disclose if she has any concerns

57
Q

Haematology in antenatal care

A

Check for anaemia
Check for rhesus status, and screened for atypical red cell alloantibodies at the beginning and end of pregnancy
If women are at high risk screen for haemaglobinopathies

58
Q

Infection screening in antenatal screening

A

Routinely we screen for: asymptomatic bacteruria,

Hep B, HIV, Rubella susceptibility and syphilis

59
Q

Pregnancy related conditions which should be considered during care

A

Gestational diabetes
Pre-eclampsia
Gestational chloestasis

60
Q

Raised maternal serum a-fetoprotein

A

Open neural tube defect

61
Q

Ultrasound “banana” and/or “lemon” sign of cerebellum

A

Chiari II malformation and <24wks spina bifida

62
Q

Alpha-Fetal Protein levels

A

Low levels indicate Downs but high levels indicate a break in the skin which may be due to spina bifida.

63
Q

Timing of Twin division

A

Dizygotic - seperate eggs
Monozygotic dichorionic –> divide before 3days, monochorionic, diamnoitic –> between 4-7 days,
Monochorionic, monoamnitotic or conjointed –> after 7 days.

64
Q

Basic downs risk by age

A

1/1,000 at 30 then divide by 3 for every 5yrs.

Obstetrics (13 decks)

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