CMV in pregnancy

Question 1

Pathophysiology

Answer 1

• Most common congenital infection
  -Risk factors for infection
• Child-care worker – 12.5% annual seroconversion
• Transmission via urine/saliva contact
• 50% of women are immune
  Transmission mainly related to primary infection in pregnancy and depends on GA at infection
• Risk of infection increases with GA BUT risk of fetal damage decreases with increasing GA
  -T1 and T2: 40% risk of transmission with 10% risk of fetal damage
• T3: 80% risk of transmission but nil fetal damage seen after 27 weeks
• Recurrent infection has transmission risk of 1-2%

Question 2

Clinical Assessment

Answer 2

• History and examination
  o Most infections are asymptomatic but primary infections can have mild illness with fever, lethargy, malaise
• Investigations
  o CMV serology
• IgM remains in circulation for months and can be positive in reinfection
• If IgG + and IgM + check IgG avidity
  o Fetal investigation in confirmed maternal infection
• Ultrasound (low sensitivity/specificity) >6/52 after infection
• Microcephaly, hydrocephalus, intracranial calcification
• Hydrops, ascites, polyhydramnios, pleural effusions
• IUGR, oligohydramnios
• Echogenic bowel, pseudomeconium ileus
  § Amniocentesis
• CMV PCR
• Most sensitive if taken after 21/40
  o High specificity at all gestations
• Positive PCR is not predictive of fetal damage

Question 3

Management

Answer 3

• Referral to specialist MFM service is essential
• No proven therapies to prevent fetal transmission or reduce fetal sequelae
  1 RCT shows CMV specific hyperimmune globulin may prevent congenital infection
  o Termination may be considered, especially if USS abnormalities
• Counselling
  o Primary infection in pregnancy
• 30% chance of fetal transmission
• 10% symptomatic at birth
• Increased mortality
• Microcephaly, seizures, hearing loss, chorioretinitis
• Purpura, hepatosplenomegaly, jaundice, pneumonia
• 50% have long term sequelae
• 90% asymptomatic at birth
• Risk of hearing loss, chorioretinitis
• 10% have long term sequelae
  o Reinfection or reactivation in pregnancy
• 1% risk of fetal transmission
• <1% risk of symptomatic CMV
• Neonatal review by neonatologist
  o Full examination, ophthalmology assessment, cranial USS
  o Serology for CMV IgM and urine and saliva for CMV PCR
  o Long-term follow-up for children diagnosed with congenital CMV