Antenatal Care Flashcards
What percentage of the UK pregnant population are offered invasive screening per year?
a. 0.5%
b. 1%
c. 2.5%
d. 5%
e. 7.5%
D - 5%
Approximately 30,000 women are offered invasive prenatal diagnostic testing each year in the UK – equivalent to around 5% of the total obstetric population.
What is the maximum outer-gauge needle size used in diagnostic amniocentesis?
a. 0.3mm
b. 0.5mm
c. 0.9mm
d. 1.0mm
e. 1.2mm
C - 0.9mm
The maximum (outer) needle gauge for use in amniocentesis procedures is 0.9mm, equivalent to 20G. There is no firm evidence on the maximum diameter recommended for CVS.
A subspecialty trainee is learning to perform amniocentesis and CVS. What is the minimum number of procedures performed per annum required to maintain competency in invasive testing?
a. 30
b. 50
c. 75
d. 100
e. 120
A - 30
The RCOG advise that those performing invasive procedures should be performing a minimum of 30 per annum to maintain competency. Rates of miscarriage are estimated in some studies to be up to 6-8x higher amongst less experienced when compared with ‘very experienced’ operators performing >100 procedures per annum. The guideline does not set 30 as an absolute minimum threshold though suggests that those performing less than 30 procedures each year should meticulously audit their own data to evidence safety.
A patient attends for a CVS following a high risk combined test result. On first pass, the operator is unsuccessful in obtaining a satisfactory specimen. What is determined to be an acceptable ‘second insertion’ rate for a given practitioner in invasive testing?
a. 1 in 100
b. 3 in 100
c. 4 in 100
d. 6 in 100
e. 7 in 100
E - 7 in 100
7 cases of ‘second-insertion’ per 100 consecutive procedures is quoted as the upper limit of acceptability. Guidelines suggest that in all cases, no more than 2 attempts should be made by a single practitioner – if unsuccessful twice, a more experienced or senior operator should take over.
What is the quoted risk of severe maternal sepsis following amniocentesis or CVS?
a. <1 in 1000
b. 2 in 1000
c. 5 in 1000
d. 7 in 1000
e. 1 in 100
A - <1 in 1000
Severe sepsis (including maternal death) is reported following invasive testing though is rare (<1 in 1000). Potential routes of infection include skin contaminants, inadvertent bowel perforation or organisms present on the probe or gel. Use of a sterile field, sterile gel, probe covers and aseptic precautions help to decrease the risk.
With continuous ultrasound visualisation of the needle, what is the incidence of blood-stained specimen collection (‘bloody tap’) in amniocentesis?
a. 1/100
b. 4/100
c. 1/1000
d. 8/1000
e. 15/1000
D - 8/1000
The incidence of blood-stained amniocentesis varies, though with continued visualisation of the needle throughout the procedure, is reduced from ~2.4% to 0.8% - equivalent to 8 bloody taps per 1000 procedures.
What is the maximum gauge of the outer needle used in amniocentesis?
a. 22G
b. 20G
c. 16G
d. 14G
e. 12G
B - 20G
The maximum (outer) needle gauge for use in amniocentesis procedures is 0.9mm, equivalent to 20G. There is no firm evidence on the maximum diameter recommended for CVS.
In additional to the increased rate of fetal loss, which of the following is increased in those undergoing ‘early’ amniocentesis (i.e. <15/40) compared with when the procedure is performed beyond 15/40?
a. Fetal growth restriction
b. Bloody tap
c. Talipes
d. Long bone deformities
e. Neural tube defects
C - Talipes
While technically possible, amniocentesis generally should not be performed prior to 15+0/40 owing to an increased risk of fetal loss, talipes and respiratory morbidity compared with procedures performed after 15/40.
A Para 3 attends for review in fetal medicine at 14+2/40 after receiving a ‘high-risk’ result on her combined screening. She opts for invasive testing. Within which gestational age timeframe can chorionic villus sampling be performed?
a. 9+0 > 14+6
b. 10+0 > 13+6
c. 11+0 > 13+6
d. 12+0 > 14+6
e. 12+0 > 15+6
C - 11+0 > 13+6
CVS may be performed either transabdominally or transcervically (dependent on operator experience) between 11+0 and 13+6 weeks gestation. Amniocentesis should not be performed earlier than 15+0/40. The patient in the scenario will require an amniocentesis.
A patient attends the fetal medicine clinic at 15+2/40. She was originally seen with a ‘high-risk’ result on combined screening at 13/40 though it was not possible to perform a CVS owing to placental position. She now wishes to proceed with an amniocentesis. What is the increased risk of miscarriage associated with amniocentesis in addition to background risk?
a. 0.5%
b. 1%
c. 1.5%
d. 2%
e. 2.5%
B - 1%
Women should be informed that the ‘additional’ risk of miscarriage following amniocentesis (that is to say, in addition to existing background risk) is 1% with a ‘slightly higher’ risk for CVS (the guideline does not commit to a number). Several large cohort studies have suggested that the true rate is probably lower, though 1% should be used in counselling patients.
A late-booker is offered invasive testing after undergoing her first scan in pregnancy at 31/40. Unfortunately this scan highlights a number of abnormalities which may indicate a chromosomal abnormality. Compared with second trimester amniocentesis, which of the following is increased when the procedure is performed in the third trimester?
a. Emergency delivery
b. Oligohydramnios
c. Fetal growth restriction
d. Bloody tap
e. Infection
D - Bloody Tap
Third trimester amniocentesis is associated with a higher risk of bloody tap (est. 5-10% in one study) and (perhaps surprisingly) multiple attempts (est. 5%) when compared with second trimester procedures. This may be in part attributable to the fact that in addition to late karyotyping as required in this scenario, a number of third trimester procedures are carried out with the intention of detecting suspected fetal infection in the setting of PPROM.
A patient who is HIV positive attends for invasive screening after a high risk quadruple test. She is taking highly active anti-retroviral therapy (HAART) and has an undetectable viral load and normal CD4 count. What threshold is advised before undertaking invasive testing in HIV positive mothers?
a. Viral load <1000 copies/ml
b. Viral load <400 copies/ml
c. Viral load <100 copies/ml
d. Undetectable viral load
e. Invasive testing is contraindicated in HIV positive patients
D - Undetectable viral load
All patients undergoing invasive testing should have their blood-borne virus status reviewed prior to the procedure. In HIV positive patients, consideration should be given to delaying the procedure until there is no detectable viral load in patients on treatment. In patients not currently on anti-retroviral therapy, this should be considered before invasive testing is performed. Testing can be performed on women who carry Hep B or C though evidence to support this is lacking. The limited data available appears to suggest the risk of transmission is very low (Hep B) or not increased at all (Hep C). It is worth noting that the exact terminology used differs slightly between the RCOG Green Top Guideline (which states that an ‘undetectable’ viral load must be achieved prior to invasive testing) and the BHIVA Guideline on HIV in Pregnancy (which states <50 copies/ml, though surrounding text suggests that this threshold and ‘undetectable’ may be considered interchangeable).
The varicella zoster virus which causes chickenpox belongs to the family of Human Herpes viruses – which number is it allocated?
a. 1
b. 2
c. 3
d. 4
e. 5
C - 3
Varicella zoster belongs the human herpes-virus family of DNA viruses. It is also known as human herpes-virus 3.
What is the incubation period of chickenpox infection?
a. 1-2 days
b. 4-5 days
c. 7-10 days
d. 7-21 days
e. 3-4 weeks
D - 7-21 days
Chickenpox has an incubation period ranging from 1-3 weeks; or 7-21 days
How long prior to appearances of the chickenpox rash does an infected individual become capable of passing on the virus?
a. At the time of the rash appearing
b. 24 hours
c. 48 hours
d. 72 hours
e. 5 days
C - 48 hours
Individuals with chickenpox are potentially infectious from approximately 48 hours prior to the appearance of the rash until all vesicles have crusted over. This has implications for susceptible pregnant women who may have exposure to an infected individual without knowing it as the rash is yet to appear.
What is the approximate incidence of primary VZV infection (chickenpox) in pregnancy in the UK?
a. 3 in 10,000
b. 3 in 1000
c. 7 in 10,000
d. 7 in 1000
e. 1 in 300
B - 3 in 1000
90% of women in the UK are seropositive for VZV although the number may be considerably lower in women from overseas, particularly those from the tropics. It is not routine practice in the UK to test booking bloods for VZV IgG though this can be done on request if required – usually a simple enquiry about a past history of chickenpox will suffice. Around 3 in 1000 pregnancies are complicated by chickenpox on average.
What percentage of individuals in the UK are seropositive for varicella zoster virus (chickenpox) IgG?
a. 50%
b. 60%
c. 75%
d. 90%
e. 95%
D - 90%
90% of women in the UK are seropositive for VZV although the number may be considerably lower in women from overseas, particularly those from the tropics. It is not routine practice in the UK to test booking bloods for VZV IgG though this can be done on request if required – usually a simple enquiry about a past history of chickenpox will suffice. Around 3 in 1000 pregnancies are complicated by chickenpox on average.
You are asked to review a patient on the post-natal ward who is known to be VZV (chickenpox) seronegative and has been advised to have post-partum vaccination. She asks for more information on the vaccine – specifically how the vaccine is administered. How do you counsel her?
a. Single dose live-attenuated vaccine.
b. Single dose inactivated vaccine
c. Two dose live-attenuated vaccine, 4-8 weeks apart
d. Two dose inactivated vaccine 3-4 months apart
e. Two dose subunit/conjugated vaccine, 4-8 weeks apart
C - Two dose live-attenuated vaccine, 4-8 weeks apart
Vaccination for VZV is via a live-attenuated vaccine given in 2 doses 4-8 weeks apart. As it is a live vaccine it cannot be given in pregnancy though may be given postnatally or pre-conceptually. Deferring pregnancy for 4 weeks after the second dose is advised however. It is safe for women who have been vaccinated to be around pregnant women though not if a post-vaccine rash appears - while this is unlikely, cases of transmission of vaccine virus have been reported. Small studies have failed to detect evidence of the vaccine in breast-milk when given postpartum thus it is safe to breastfeed.
A patient on the postnatal ward requires vaccination against chickenpox. She is keen to breastfeed though has some concerns regarding the safety of the vaccine in breastfeeding. She is also hopes to rely on breastfeeding for contraception initially though asks about whether or not falling pregnant after the vaccine would be an issue. What do you tell he?
a. Breastfeeding safe though avoid pregnancy for 4 weeks
b. Breastfeeding safe, no restrictions on pregnancy
c. Avoid vaccine while breastfeeding and avoid conception for 4 months
d. Avoid vaccine while breastfeeding, no restrictions on pregnancy
e. Avoid vaccine while breastfeeding and avoid conception for 4 weeks
A - Breastfeeding safe though avoid pregnancy for 4 weeks
Vaccination for VZV is via a live-attenuated vaccine given in 2 doses 4-8 weeks apart. As it is a live vaccine it cannot be given in pregnancy though may be given postnatally or pre-conceptually. Deferring pregnancy for 4 weeks after the second dose is advised however. It is safe for women who have been vaccinated to be around pregnant women though not if a post-vaccine rash appears - while this is unlikely, cases of transmission of vaccine virus have been reported. Small studies have failed to detect evidence of the vaccine in breast-milk when given postpartum thus it is safe to breastfeed.
What time frame spent in the same room or large open ward, is considered the minimum to qualify as ‘significant contact’ with VZV in a non-immune patient?
a. 5 minutes
b. 10 minutes
c. 15 minutes
d. 20 minutes
e. 30 minutes
C - 15 minutes
‘Significant exposure’ is defined as contact in the same room, face to face or in a large open ward for 15 minutes or more with an infectious individual.
You receive a phone call from a GP looking for advice regarding a primigravidae at 18/40 gestation, originally from Tanzania, who spent 30 minutes playing with her nephew yesterday. Today however she has been informed that the child has developed a chickenpox rash. The patient does not recall ever having had chickenpox herself. What immediate action do you recommend?
a. No action required as child was not infectious at time of contact
b. No action required as the contact was not significant
c. Immediate VZIG
d. VZV vaccination urgently
e. Blood test for VZV IgG
E - Blood test for VZV IgG
As the patient does not recall having had chickenpox herself, she is at risk of primary infection in pregnancy which is associated with significant maternal and potential fetal morbidity. While 90% of British women are infact seropositive, women from the tropics are less likely to be. While the child in the scenario did not have a rash at the time of contact, the rash has appeared in the subsequent 48 hours thus he was infact infectious at the time. The first step is to ascertain the patient’s IgG status which can be done by either testing her stored booking sample or from a blood test now.
You receive a phone call from a GP looking for advice regarding a primigravidae at 18/40 gestation, originally from Tanzania, who spent 30 minutes playing with her nephew yesterday. Today however she has been informed that the child has developed a chickenpox rash. You check the woman’s stored booking sample which tests negative for VZV IgG and thus recommend a course of VZIG urgently. The woman informs the GP that she is unable to wait for this today but may return tomorrow. How long after exposure is VZIG thought to be effective in such a setting?
a. 24 hours
b. 48 hours
c. 5 days
d. 10 days
e. 15 days
D - 10 days
VZIG may be given up to 10 days after significant exposure in susceptible individuals thus there is usually always time to check IgG status rather than rushing to administer needlessly.
A primigravida who received VZIG the previous day, following a significant exposure to chickenpox, informs you that her sister is coming to stay with her for a few days the following week. She is also pregnant and the patient asks whether or not there is any risk of her passing VZV on to her sister. How long after exposure to chickenpox should women be regarded as infectious when given VZIG?
a. 7-10 days
b. 7-14 days
c. 8-21 days
d. 8-28 days
e. Women given VZIG are not at risk of passing the virus on
D - 8-28 days
Patients with a history of significant exposure must be treated as potentially infectious regardless of whether they receive VZIG or not as there remains a possibility of them developing infection. While the incubation period of chickenpox is known to be 7-21 days, those who receive VZIG should be treated as potentially infectious for an additional 7 days – i.e. from 8-28 days. Patients who do not receive VZIG after significant exposure should be managed as potentially infectious throughout the incubation period – i.e. from 8-21 days.
How long should non-immune exposed women who are not given VZIG be regarded as potentially infectious?
a. 7-10 days
b. 7-14 days
c. 8-21 days
d. 8-28 days
e. 10-14 days
C - 8-21 days
Patients with a history of significant exposure must be treated as potentially infectious regardless of whether they receive VZIG or not as there remains a possibility of them developing infection. While the incubation period of chickenpox is known to be 7-21 days, those who receive VZIG should be treated as potentially infectious for an additional 7 days – i.e. from 8-28 days. Patients who do not receive VZIG after significant exposure should be managed as potentially infectious throughout the incubation period – i.e. from 8-21 days.