CMV in pregnancy

Background

• Infection with cytomegalovirus during pregnancy
• Infection can be primary infection, non-primary reinfection with another strain, or non-primary reactivation of latent virus
• Mainly of concern because of the risk of causing congenital CMV

Epidemiology

• Maternal seroconversion in about 2% of pregnancies
  • Higher in childcare workers
• Affects about 1 in 200 live births in US
• Risk of transmission to fetus is highest with maternal primary infection, and much lower for non-primary infection
  • Primary infection: 30% risk of congenital CMV
  • Non-primary:
    • Reinfection: 5% risk
    • Reactivation: 1% risk
• Risk of transmission to fetus following primary infection increases with gestational age, but risk of neurological sequelae decreases substantially1

Maternal Serostatus	Trimester	Transmission to Fetus	Severity of Neurological Disease			Overall Probability (of any neurological disease)
			Severe	Mild/Transient	None
Primary	first	30%	5%	30%	65%	10%
	second	40%	0%	15%	85%	6%
	third	70%	0%	0%	100%	0%
Reinfection	overall	5%				<1%
Reactivation	overall	1%				<1%

Diagnosis

• Serology with IgM and IgG
  • IgM usually positive for 6 weeks after primary infection, but can remain positive for as long as 12 months
  • IgM has false positives, including from rheumatoid factor, EBV infection, lupus

IgG	IgM	Avidity	Interpretation
+	–	N/A	past infection, low risk for congenital infection
+	+	high	past infection, low risk for congenital infection
+	+	low	primary maternal infection within the past 3 months
–	–	N/A	either no infection, or repeat in 4 weeks

• Fetal infection is confirmed by amniocentesis sent for PCR
  • To minimized the risk of a false-negative result, it should be be done after 17 weeks gestation and at least 7 weeks after maternal infection

Management

• Counsel mother on risk of fetal infection and subsequent development of congenital CMV
• If they would terminate if CMV-positive due to those risks, then proceed with amniocentesis to diagnose