Antenatal screening Flashcards

1
Q

What are the principles of screening?

A
Highly sensitive
Highly specific
High positive predictive value 
Easily used in a large population 
Safe and cheap
Quick and straightforward to perform 
Able to detect a disease with a known natural history and where early diagnosis has a proven benefit
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2
Q

How is sensitivity assessed?

A

True positive/ (positive + false negative)

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3
Q

How is specificity assessed?

A

True negative / (negative + false positive)

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4
Q

What eye screening is offered to diabetic women in pregnancy?

A

DE screen when first present for care

DE screening anually

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5
Q

What bloods should be taken off in the 1st trim?

A

Sickle cell and thalassaemia
IF WANTED; blood test for DSS
Syphilis, hep B and C, HIV and rubella susceptibility
Haemaglobin, group, rhesus and red cell antibodies

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6
Q

When are scans performed in pregnancy?

A

At booking app; 11-13 weeks

Anomaly scan at 20 weeks

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7
Q

What does the newborn gurthrie prick test for?

A
CF
Congenital hypothyroidism 
Sickle cell 
Metabolic disorders: 
Phenylketonuria (PKU)
medium-chain acyl-CoA dehydrogenase deficiency (MCADD)
Maple syrup urine disease (MSUD) 
Isovaleric acidaemia (IVA) 
Glutaric aciduria type 1 (GA1) 
Homocystinuria (pyridoxine unresponsive) (HCU)
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8
Q

What is performed at the booking visit?

A
Hx; 
Menstruation 
Medical
Obstetric
Family
Social 
Exam: 
BMI 
BP
CVS
Abdominal
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9
Q

What is the cut off for BMI in terms of allowing for midwife led care in place of obstetric lead care?

A

BMI of 40 needs to be under care of obstetrician

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10
Q

What is naegele’s rule?

A

Predicts an EDD based on LMP

Add on 9 months and 7 days to arrive at due date

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11
Q

What is the most accurate measurement of EDD?

A

CRL on USS

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12
Q

What investigations are performed at the booking visit?

A
Bloods; 
Hb
ABO 
Rhesus
Syphilis
HIV
Hep B and C 
Urinalysis; MSSU, C+S
USS
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13
Q

What is assessed on USS at the booking visit?

A
Confirm viability 
Singleton/ multiple pregnancy
Estimate gestational age
Detect major structural anomalies; abdominal wall defects or anencephaly 
Offer DSS
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14
Q

Where should you look if there is an empty sac but a positive pregnancy test?

A

Adnexae for ectopics

Do hCG level to monitor

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15
Q

What are the different types of twins?

A

Dichorionic/ diamniotic
Monochorionic/ diamniotic
Monochorionic/ monoamniotic
Conjoined

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16
Q

What is assessed at follow up antenatal visits with the midwife post booking appointment?

A

Hx; physical and mental health, foetal movements
Exam: BP and urinalysis, symphysis (fundal height(, lie and presentation, engagement of presenting part, foetal heart auscultation

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17
Q

Which are the main anomalies incompatible with life?

A

Major heart abnormalities
Anencephaly
Trisomy 13 and 18

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18
Q

What is assessed in the H+N in anomaly scan?

A

Skull
Nunchal skin fold
Brain; cavum septum pellucidum, ventricular atrium, cerebellum

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19
Q

What is assessed in the face in anomaly scan?

A

Lips; cleft lip

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20
Q

What is assessed in the chest in an anomaly scan?

A

Heart; four chambers. outflow tracts

Lungs

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21
Q

What is assessed in the abdomen in an anomaly scan?

A

Stomach; stomach and short intra-hepatic section of umbilical vein
Abdo wall; bowel, renal pelvis
Bladder

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22
Q

What is assessed in the spine in an anomaly scan?

A

Vertebrae

Skin covering

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23
Q

What is assessed in the limbs in an anomaly scan?

A

Femur
Hands; metacarpals
Feet; metatarsals

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24
Q

What is assessed in the uterine cavity in an anomaly scan?

A

Amniotic fluid

Placenta

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25
What are the main foetal anomalies picked up on the 20 wk scan?
``` Anencephaly Open spina bifida Cleft lip Diaphragmatic hernia Gastroschisis Exomphalos Serious cardiac abnormalities Bilateral renal agenesis Lethal skeletal dysplasias Edwards syndrome (trisomy 18) Patau's sundrome (trisomy 13) ```
26
What is placental praevia?
Placenta is low lying in the womb and covers all or part of the cervix In most women, as the women grows upwards, the placenta moves with it so that it is in a normal position before birth
27
What should be offered if a low lying placenta is seen at the anomaly scan?
Scan at 32 weeks | If this is unclear, vaginal scan
28
What is the recommendation for women with placenta praevia?
C-section
29
How is down's syndrome assessed in the 1st trim?
Measure of nuchal thickness; >3.5mm is bad | PAPP-A and hCG blood testing
30
How should a risk of down's syndrome be estimated?
hCG (goes up) PAPP-A (goes down) NT Maternal age
31
What is PAPP-A?
It is produced by the placental syncytiotrophoblast and deciduas. It increases the bioavailability of insulin like growth factor, which in turn mediate trophoblast invasion and modulates glucose and amino acids transport in the placenta
32
What down's risk assessment can be performed in 2nd trim?
Blood sample at 15-20 wks | Assay of hCG and AFP
33
What is considered high risk for down's syndrome?
>1:250 change | Then a scan is arranged with amniocentesis
34
What can a thickened nuchal thickness indicate?
Chromosomal defect Foetal death Major foetal anomaly Much more unlikely to have a foetus alive and well
35
What maternal markers are used for 2nd trim screening for aneuploidy?
AFP hCG Unconjugated oestradiol (UE3) Inhibin A
36
When is an amnio performed?
After 15 weeks
37
What is the rate of miscarriage from an amniocentesis?
1%
38
When is chorionic villus sampling (CVS) performed?
After 12 weeks
39
What is the miscarriage rate for CVS?
2%
40
What are the 2 major hemoglobin disorders?
Sickle cell | Thalassemias
41
What is the rate and mode of inheritance of sickle cell and thalassemia?
AR 50% risk of carrier 25% risk affected 25% risk carry nothing
42
What does a normal haemoglobin contain?
Haemaglobin A: | 2 alpha and 2 beta chains
43
What is the difference between HbS and thalassemias?
HbS; mutation results in a change to the structure and quality of hemoglobin variants Thalassaemias; amount of hemoglobin the body produces is reduced, impacting on its oxygen carrying capacity
44
Risk of HbS in pregnancy?
``` Stroke, VTE, meningitis Miscarriage Infection Still birth Pelvic inflammation Papillary necrosis Bone crisis Amnionitis Anaemia Pulmonary cx Premature birth Hypertx Placenta praevia Maternal mortality ```
45
What are the different types of maternal anaemia?
Iron deficiency Folate deficiency B12 deficiency
46
Why is maternal Hb optimised for birth?
To prevent fatal PPH
47
What is foetal hydrops?
Serious condition Abnormal accumulation of fluid in 2 or more foetal compartments: Ascites Pleural effusion Pericardial effusion Skin oedema Can be assoc with polyhydramnios and placental oedema
48
What is rhesus disease?
Haemolytic disease of the newborn; In a foetus; anaemia In a newborn; anaemia and jaundice
49
How can foetal anaemia be assessed?
Doppler to assess increased flow in the middle cerebral artery; indication that the baby is hypoxic and anaemic
50
What rhesus of the mother puts the baby at risk?
Rhesus neg
51
What are RF for gestational diabetes?
BMI > 30 Previous macrosomic baby weighing 4.5kg (9 pounds 9) or above Previous gestational diabetes FMHc of diabetes Minority ethnic family origin with high prevalence of diabetes
52
What is the gold standard for diagnosis of gestational diabetes?
2hr 75g oral glucose tolerance test FPG; 5.6 mmol/l 2hr OGTT; 7.8 mmol/l
53
At what gestation is the fundal height around the umbilicus?
20 weeks
54
At what gestation is the fundal height at the xiphisternum?
36 wks
55
What are major risk factors for SGA foetus?
``` Maternal age over 40 Smoker > 11 cigs Paternal SGA Cocaine Daily vigorous exercise Previous SGA baby Previous stillbirth Materna SGA Chronic hypertx Diabetes with vascular disease Renal impairment Antiphospholipid syndrome Heavy bleeding similar to menses PAPP-A < 0.4 MoM ```
56
What screening is performed for SGA foetus?
Reassess at 20 wks PAPP-A <0.5 MoM Foetal echogenic bowel
57
What should be performed if baby still small at 20 weeks?
Serial assessment of foetal size and umbilical artery doppler from 26-28 weeks Reassess during 3rd trim
58
How is foetal growth assessed?
Serial measurement of SFH at each antenatal app from 24wks of pregnancy Plot SFH on customiased chart
59
At what cut off should women with a reduced SFH have further assessment?
Below 10th centile or serial measurements which demonstrate slow or static growth by crossing centiles Refer for USS measurment
60
In what conditions is SFH inaccurate?
BMI >35 Large fibroids Hydraminos
61
What are the major risk factors for pre-eclampsia?
``` Hypertensive disease in a previous preg CKD Autoimmune disease such as SLE or APS T1DM or T2DM Chronic hypertx ```
62
What is the treatment for high risk patient groups for PET?
75 mg of aspirin daily from 12 wks until birth at baby
63
What are the moderate risk factors for PET?
``` First preg Age 40 or over Pregnancy interval of >10 years BMI >35 FMHx of PET Multiple pregnancy ```
64
What is the recommendation for women with more than 1 moderate risk factor for PET?
75mg of aspirin from 12 weeks until birth of baby
65
What is urinalysis assessing in antenatal screening?
UTI Asymptomatic bacteriuria (send MSSU for C+S) PET; proteinuria Diabetes
66
What are the minor RF for SGA foetus?
``` Maternal age >35 IVF singleton Nulliparity BMI <20 BMI 25-34.9 Smoker 1-10 cigs Low fruit intake pre-preg Previous PET Pregnancy interval <6 months Pregnancy interval >60 monthd ```
67
How many minor risk factors are needed to warrant further screening for SGA?
3 or more
68
How should SGA be assessed if minor risk factors are found?
``` Reassess at 20 wks PAPP-A <0.4 Foetal echogenic bowel Uterine artery doppler at 20-24 weeks Assessment of foetal size and umbilical artery doppler in 3rd trim ```
69
What ia nuchal thickness?
Measure of skin thickness behind foetal neck using USS | Assess fluid levels
70
What is considered an abnormal nuchal thickness?
<3.5 mm when CRL is between 45-85mm (11-13 +6)