Parvovirus in Pregnancy

Question 1

Pathophysiology

Answer 1

• Spread via respiratory secreations or hand to mouth contact
• Cytotoxic to red blood cell precursors

Question 2

Epidemiology

Answer 2

• 40% women are at risk of infection
  -Risk depends on exposure
  50% risk if susceptible and exposure is at home
  20% risk if exposure is in community
• Risk of transmission to fetus depends on GA at infection
  In general increasing GA has increased transmission rate
  <15w: 15%
  15-20w: 25%
  20w to term: 70%

Incubation period 5-7 days
Infectious from 3-10/7 post exposure (Until rash disappears)

Adults may be asymptomatic
OR have Erythema Infectiosum (Fifth disease)

Question 3

Complications

Answer 3

Proven maternal infection in <20w pregnancy
- 10% risk of miscarriage
- 3% risk of hydrops
§ 32% spontaneously resolve
§ 33% die prior to IUT
§ 27% resolve after IUT
§ 6% die after IUT
- 0,6% risk of fetal loss post treatment

NOT teratogenic therefore no increased risk of congenital malformation
- small risk of fetal thrombocytopaenia

> 20w pregnancy:
- <1% risk of fetal loss
- <0,3% risk of hydrops

Question 4

Clinical assessment

Answer 4

• History
  o Symptoms of infection
• 20-25% of adults are asymptomatic
• Slap-cheek rash rare in adults
• Symmetrical polyarthropathy occurs in 80%
  o Assess nature of exposure
• Examination
  o Vitals
  o Evidence of rash or arthropathy
  o Cardiorespiratory examination
  o Fetal heart +/- CTG
• Investigations
  o FBE
• May cause transient maternal anaemia
  o Parvovirus B19 serology (IgM and IgG)
• IgG+ IgM-
• Likely represents past infection and immunity
• If clinical concern, check paired serology from booking bloods
• If IgG- at booking, antenatal infection confirmed
• IgG- IgM-
• Susceptible
• Repeat serology in 2 weeks
• IgG- -> no infection
• If IgG+ -> recent infection
  *
  -IgG- IgM+
• ? recent infection
• Repeat serology in 2 weeks
• IgG- -> false positive IgM
• If IgG+ -> recent infection
• IgG+ IgM+
• Confirmed infection

Question 5

Management

Answer 5

• Education and counselling
  o Risks of fetal loss and hydrops
• Referral to MFM unit
• Surveillance for fetal anaemia
  o Weekly ultrasound assessment of MCA PSV from 16/40 until 30/40 or for 12/52 after diagnosis, whichever is sooner
  o If MCA PSV >1.5 MoMs -> requires cordocentesis +/- IUT
• Management of fetal anaemia
  o Intrauterine transfusion
• Platelets should also be available for transfusion
• Send blood sample for Parvovirus PCR to confirm diagnosis
• Delivery
  o Timing
• Delivery at term if hydrops resolved
• If ongoing hydrops/anaemia, delivery timing individualised with risk/benefit assessment
  o Intrapartum
• CS for obstetric indications (ie hydrops)
• CEFM recommended as anaemia increases risk of fetal acidosis
• Post-partum
  o Neonatal follow-up for 1 year due to risk of congenital aplasia