When a pregnant individual receives a Cytomegalovirus (CMV) IgG positive test result, it indicates their body has previously encountered the virus. This means specific IgG antibodies are present in their blood, signifying a past infection rather than a current, active one.
Understanding Cytomegalovirus
Cytomegalovirus (CMV) is a very common virus. Many healthy individuals who contract CMV experience no symptoms, or only mild, flu-like symptoms. This virus can be transmitted through close contact with various body fluids from an infected person, including saliva, urine, blood, tears, breast milk, and through sexual contact.
Meaning of an IgG Positive Result
The immune system produces different types of antibodies in response to a viral infection. IgG antibodies are produced later in an infection and remain in the bloodstream for a long time, providing long-term immunity. Their presence indicates a past CMV infection and a developed immune response. This differs from IgM antibodies, which are produced earlier and indicate a more recent or active viral presence.
Healthcare providers may utilize an avidity test to gain insight into the timing of a past infection. High avidity results suggest the infection occurred many months ago. Conversely, low avidity results can suggest a more recent infection. An IgG positive result, especially with high avidity, is reassuring because it indicates the mother has established immunity to the virus.
CMV and Fetal Health
A primary concern for pregnant individuals is the potential impact of CMV on fetal health. When a mother has a pre-existing CMV IgG positive status, the risk of transmitting the virus to the baby (congenital CMV) is lower compared to a primary infection occurring during pregnancy. Maternal antibodies from a past infection provide protection, helping prevent the virus from crossing the placenta or mitigating its effects. This protective effect reduces the likelihood of severe outcomes for the baby.
While rare, it is possible for a non-primary CMV infection to occur during pregnancy. Even in these instances, the risk of congenital CMV is much lower, less than 1-2%, compared to the 30-40% risk associated with a primary infection. When transmission occurs from a non-primary infection, the resulting congenital CMV is often milder or asymptomatic for the infant, highlighting the protective role of pre-existing maternal immunity.
Next Steps and Monitoring
Following an IgG positive result, a healthcare provider will review avidity test results. If the timing of the past infection remains uncertain, an IgM test might be considered, though a positive IgM with high avidity IgG is less concerning. Routine ultrasounds monitor fetal development, but specific concerns for CMV are low with an IgG positive status. Invasive procedures like amniocentesis are not recommended unless other risk factors or anomalies are identified. It is important to discuss all test results and any recommended follow-up with your healthcare provider.
Reducing CMV Risk
Even with a positive CMV IgG status, individuals can still shed the virus intermittently. Adopting general hygiene practices remains beneficial for reducing viral transmission. Frequent handwashing is recommended, especially after contact with young children’s saliva, tears, or urine. Avoiding the sharing of food, drinks, or eating utensils with others, particularly young children, also helps to minimize potential viral spread. These measures contribute to general health and reduce the circulation of various common viruses.