perinatal infection Flashcards
What is the risk of transmission of CMV if primary infection occurs in pregnancy?
30%
If CMV is transmitted in pregnancy to the fetus, what is the risk that the fetus/neonate will be affected?
Symptomatic in 10-15%
Asymptomatic in 85-90%
If the fetus or neonate are affected by CMV (only 30% transmission, and of those only 10% affected) what is the risk of sequelae?
50% (50% affected with sequelae, 50% affected but with no sequelae)
Of the fetus or neonates that are asymptomatic with infection what is the risk of sequelae?
10-15%
How do you ascertain whether a woman has primary or secondary CMV?
Testing of IgG and IgM
- if IgG positive and IgM positive avidity testing required (low = recent primary infection, high = old infection)
- if IgG negative and IgM positive then repeat test in 2/52
What investigations are possible to review fetal risk if CMV testing indicates primary infection in pregnancy
Fetal USS and fetal MRI - sensitivities of 30-50% and low specificity
Amniocentesis - if performed <20/40 45% sensitive, high specificity, if performed >20/40 80-100% sensitive and high specificity
What investigations are possible to review fetal risk if CMV testing indicates primary infection in pregnancy
Fetal USS and fetal MRI - sensitivities of 30-50% and low specificity
Amniocentesis - if performed <20/40 45% sensitive, high specificity, if performed >20/40 80-100% sensitive and high specificity
How can you increase sensitivity of amniocentesis for fetal screening?
by waiting >6 weeks following maternal infection
what does fetal amniocentesis for CMV actually test?
CMV PCR
What would you advise a woman with +ve fetal screening for CMV
Positive result cannot predict the degree of fetal damage
What are the 3 main concerns for symptomatic congenital CMV infection?
- early mortality (first 3/12 of life) rates of 5-10%
- neurologica sequelae or microcephaly 35-50%, seizures (10%), chorioretinitis (10-20%), developmental delay (<70%)
- sensory neural hearing loss 25-50%, with progression expected in about half (mainly in the first 2 years of life)
What are the 2 main concerns for asymptomatic congenital CMV infection?
- sensorineural hearing loss (5%) with progression in about half with time
- chorioretinitis (2%)
What are the steps that need to be taken for a neonate born to a mother with primary CMV?
- thorough physical examination at birth
- serology CMV IgM or CMV PCR from saliva, blood, urine
- If +ve confirms congenital CMV
- categorise into symptomatic and asymptomatic
- if asymptomatic - 3-6 monthly reviews for first 2 years including regular hearing and neurodevelopment testing
How can you assess whether a neonate is symptomatic of congenital CMV?
- Head USS - hydrocephalus may be picked up
- brain MRI - intracranial calcifications, ventriculomegaly, cerebral atrophy, white matter abnormalities
What is the risk of transmitting HSV in the context of recurrent HSV?
HSV 1 15%
HSV 2 <0.01%
if detected in genital area at time of delivery then overall 1-3% risk
if not then overall risk 1%
what is the risk of spontaneous abortion, IUGR and pre term labour with HSV infection?
rare - <1% in either recurrent or new infection
what percentage of neonatal HSV infection is accounted for by true intra-uterine infection?
<5%
what assessment should you complete for a woman who has had her first suspected episode of HSV in pregnancy or labour?
- type specific PCR +/- genital swab/culture
- HSV type specific serology test
How would you interpret HSV 1 + genital swab
with HSV 1 and 2 IgG negative?
primary first episode of HSV infection
- would then have to consider gestation
- if well before 30-34/40 then risk of transmission is same as recurrent HSV
if the HSV is in the genital tract, the use of fetal scalp electrodes are contraindicated. What is the OR?
- increased risk of transmission, OR of 6.8
what would you advise a woman with current HSV at time of labour regarding mode of delivery?
- caesarean delivery reduces risk of transmission with OR of 0.14
what is the risk of transmission if primary HSV infection occurs at time of delivery?
25-50% risk
if HSV 1 (or2) +ve and HSV 1 (or 2) IgG +ve what would your management be?
consider suppressive antiviral therapy from 36/40 in women with multiple recurrent overt lesions
In someone who has had recurrent HSV in pregnancy and has been on suppressive acyclovir treatment what would you do at time of labour?
inspect for active lesions
- if none, then proceed to vaginal delivery
- consider avoiding FSE, forceps or ventouse, or rather be aware that these may increase risk of transmission
what is the dosing of suppressive antiviral treatment?
oral acyclovir 400mg PO TDS
oral valeclovir 500mg PO BD
what investigations are required of a baby born in condition high risk for HSV? (Mother with primary HSV at labour or genital lesions identified at labour)
- Lumbar puncture - CSF PCR, HSV PCR, viral culture
- blood count for low platelets (HSV attacks erythrocytes)
- LFT
- HSV PCR on blood
- surface swabs - eyes, throat, umbilicus, rectum, urine
- Commence IV acyclovir immediately
What treatment to babies iwht congenital HSV require?
20mg/kg IV TDS as 1-2 hour infusion
what is the treatment for listeriosis in pregnancy?
amoxicillin/ampicillin 2g IV 4-6 hourly for 14 days
what is the prognosis for the fetus if listeriosis occurs in the third trimester?
40-50% mortality rate for the fetus
how common is listeriosis in Australia?
rare - 0.3 cases per 100,000 of population
but of that 14% are pregnant women
how would you detect fetal listeria infection?
- placental, cord or post- pharyngeal granulomas
- multiple small skin granuloma
- meconium stained/discoloured liquor <34/40
- pneumonitis
- purulent conjunctivitis
what is the empiric treatment for the unwell neonate when listeria is suspected?
50mg/kg 12 hourly of either amoxicillin or ampicillin
what are the two principles used to avoid listeria infection?
- avoid high risk foods
- safe food handling practises
which foods are considered high risk for listeriosis infection>
- unpasteurised milk
- pates, dips and soft cheeses
- chilled, pre cooked seafoods
- pre cooked meat
- prepared salads
if exposed to parvovirus and results are IgG -ve and IgM -ve
or IgG -ve IgM +ve what would your next step be?
- either susceptible or recently exposed or false +ve IgM therefore repeat IgG in 2-4 weeks time
- if +ve indicates recent infection
- if -ve indicates false IgM +ve test
What makes listeria more common in pregnancy?
- intracellular infection
- reduced cell mediated immunity in pregnancy= more prone
(intracellular also means can cross BBB and placenta)
