GTG (+ other sources): Viruses in pregnancy Flashcards
What are the names of the virus responsible for chickenpox?
Varicella Zoster Virus/Human Herpes Virus 3
What type of virus is VZV?
DNA virus
What is the incubation period for VZV, Rubella, Parvovirus and Measles?
Parvovirus: 4-21 days
VZV: 7-21 days
Measles: 7-21 days
Rubella: 14-21 days
When is the infectivity period for VZV, Rubella, Parvovirus and Measles?
Parvovirus: 10 days before to day of rash
Measles: 4 days before to 4 days after
Rubella: 7 days before to 10 days after
VZV: 2 days before until vesicles crusted
What percentage of the population is seropositive for VZV, Rubella, Parvovirus, Measles?
Parvovirus: 50-60%
Measles: >95%
Rubella: 93%
Chickenpox: >90%
How frequently does primary infection with VZV occur in pregnancy?
3 in 1000 pregnancies
What type of vaccine VZV?
Live attenuated vaccine
How long does the immunity persist post VZV vaccination?
20 years
How many doses of VZV vaccine and when?
2 doses 4-8 weeks apart
Effect of VZV vaccination
Reduces primary infection 80%
Reduces mortality 2/3
How long after vaccination should pregnancy be avoided for?
4 weeks
Risks of varicella in pregnancy
Maternal risks:
- Pneumonia
- Hepatitis
- Encephalitis
- Death
Fetal varicella syndrome
Neonatal varicella infection
What percentage of mothers with VZV with contract pneumonia?
5%
Mortality rate associated with VZV in pregnancy
0-14%
When does fetal varicella syndrome occur?
Patients who contracted varicella in first 28 weeks. Virus subsequently reactivates in utero.
How often does fetal varicella syndrome occur?
1%
Features of fetal varicella syndrome
Dermatomal skin scarring
Eye defects (microphthalmia, chorioretinitis, cataracts)
Limb hypoplasia
Neurological abnormalities (microcephalic, Corsica atrophy, mental retardation, sphincter dysfunction)
Risk of miscarriage with VZV
No increase in risk of first trimester miscarriage
When does neonatal varicella infection occur?
When maternal infection occurs 1-4 weeks before delivery or immediately postpartum.
How is neonatal varicella infection contracted?
Transplacental, ascending vaginal or direct contact with lesions.
What proportion of babies whose mothers develop VZV in the 4 weeks prior or immediate postpartum period will become infected?
50% infected.
23% clinical varicella.
Management of babies born within 7 days of mothers rash or where rash occurs within 7 days of birth.
Babies should have VZIG +/- aciclovir.
What constitutes a significant contact?
Same room for 15 minutes or more
Face-to-face contact
Contact in setting of large open ward
Management of a pregnant woman who has a VZV contact?
If history of chickenpox - no further action required.
If uncertain history (or woman from tropical/subtropical country) - check booking sample for VZV IgG. If present - no further action.
If not immune then give VZIG if less than 10 days since contact (or for continuous exposure less than 10 days since appearance of rash in index case). Advise potentially infectious from 8-28 days after contact. Discuss postpartum varicella immunisation.
Management of pregnant woman with chickenpox
If <24 hours since appearance of rash and >20+0 weeks pregnant, aciclovir 800mg 5 x per day for 7 days. Consider if <20 weeks. Avoid delivery of baby until at least 7 days after rash.
If <28 weeks then refer to FMU at 16-20 weeks or 5 weeks after the infection and consider amniocentesis to detect varicella DNA.
Which pregnant women with chickenpox should be inpatients?
Severe disease - respiratory, neurological, haemorrhagic rash, bleeding.
IV Aciclovir.
RIsk of anaphylaxis with VZIG
<0.1%
Benefits of VZIG on fatal varicella syndrome
2.8% FVS if no VZIG, 0% if VZIG.
When can you give a second dose of VZIG?
Further exposure reported and 3 weeks elapsed since last dose.
What is the positive predictive value for the presence of VZV antibodies in a patient with a history of chickenpox?
99%
What type of virus is CMV?
DNA virus (herpes virus)
What percentage of pregnant population are seropositive for CMV?
Around 50%.
Within Asian population - 90%, White 45%.
What percentage of pregnant women seroconvert for CMV in pregnancy?
1-7%
What percentage of live births are affected by CMV?
0.2-2.2%
What are the consequences of congenital CMV?
12% sensorineural hearing loss
8% of cerebral palsy
Most common viral cause of congenital infection
CMV
Most common non-genetic cause of sensorineural hearing loss
CMV
What is the risk of congenital infection if mother has primary infection in pregnancy?
T1: 30%
T3: 47%
(But cases more severe and more likely to be detected antenatally in T1)
What is the risk of congenital infection if mother has secondary infection (reactivation) in pregnancy?
1-2%
What percentage of infected infants with CMV will be symptomatic at birth?
13%
What is the mortality rate associated with symptomatic congenital CMV?
30%
What proportion of infants who are asymptomatic at birth will go on to develop symptoms with CMV?
6-23%
What percentage of women will be asymptomatic with a primary infection with CMV?
90%
Who to suspect CMV seroconversion in?
- Anyone with flu-like illness
- Anyone with glandular fever and negative EBV serology
- Anyone with hepatitis and negative hepatitis serology
- Anyone with ultrasound features suggestive of CMV (only present in 25%)
How to test for maternal CMV?
- Presence of IgG in previously seronegative individual
OR - Presence of IgG and IgM of LOW avidity (<30%) suggests infection within last 3 months (>60% High avidity suggestive of infection more than 3 months ago or secondary infection)
How to confirm fetal infection with CMV?
Amniocentesis for CMV DNA - must be after 20 weeks and 6-7 weeks since infection.
Incubation period of CMV
3-12 WEEKS