Congenital Cytomegalovirus (CMV): Reducing the Risk
Published: 19 October 2020
Published: 19 October 2020
Yet, many pregnant women have never heard of this condition, and among those who are infected, most don’t even realise it. If a woman contracts the virus whilst she is pregnant, she can pass it on to her unborn baby with devastating results.
Sadly, many mothers with CMV miscarry or suffer a stillbirth, and of those babies born alive, about one in five will have problems with hearing loss, cerebral palsy or physical impairment (MAMA Academy 2019).
Cytomegalovirus belongs to the same group of viruses as the herpes simplex viruses, varicella-zoster virus and the Epstein-Barr virus. Whilst it’s a common infection that is usually harmless, once it’s in the body it remains there for life.
CMV transmission is known to occur through close contact with someone who already has the virus, the main route of transmission being direct contact with infectious bodily fluids such as urine, saliva and semen. However, for pregnant women, exposure to the urine and saliva of young children poses a particularly high risk of transmission. This is largely due to the changes in a woman’s immune system during pregnancy, which results in depressed T cell function, leaving the body at greater risk of opportunistic viral infections.
The incidence of viral illness, the intensity of viral attack and the severity of illness are all higher in pregnant women than in non-pregnant women. In addition to the immunologic changes that occur during pregnancy, hormonal changes may also predispose women to a greater risk of infection (MAMA Academy 2019).
Perhaps one of the greatest challenges presented by CMV is that most infections are asymptomatic. When symptoms are present they often mimic those of other viral infections (e.g. fever, sore throat, swollen glands, aching muscles and fatigue), meaning the presence of CMV can often go unnoticed (NHS 2017).
Approximately one in five babies born with congenital cytomegalovirus (cCMV) will suffer damage, leaving them with life-long conditions such as hearing loss, cerebral palsy and epilepsy. Despite this, relatively little advice is given about preventative measures to reduce the risk of catching CMV.
As a result, CMV Action (2019) has made the following research-based recommendations to help reduce the infection rate and minimise the risk of fetal harm.
Without doubt, the best way to reduce the risk of cCMV is to provide greater antenatal education on the simple hygiene measures that can reduce infection. These include frequent hand washing, avoiding kissing young children on the mouth and avoiding sharing food or drinks with young children.
Greater awareness about the guidelines for managing CMV is needed among midwives and other healthcare professionals so that more families receive monitoring and support.
Recent studies suggest that targeted newborn screening for babies who fail their initial hearing screening test could be a cost-effective option for detecting and reducing hearing loss caused by cCMV.
Significant advances in diagnostic technology and treatments suggest that universal screening for cCMV could allow affected children to receive treatment much more quickly.
Information on cCMV is limited and often out of date, which makes monitoring treatments and evaluating long-term outcomes unnecessarily difficult. More research-based evidence is needed in order to assess the severity of symptoms and guide clinical decision-making.
Developing a vaccine to eradicate CMV is the ultimate long term goal, although at present it’s thought that the availability of an effective vaccine may be another ten years away.<.p>
(CMV Action 2019)
As Cannon et al. (2012) suggest, awareness of CMV among women still tends to be very low, even though disabilities caused by congenital CMV are more prevalent than many other conditions. This suggests that there is a need for much greater effort to raise public awareness about how maternal infection can be prevented.
As Adler et al. (2004) point out, women who know they are pregnant tend to be highly motivated to follow preventative advice and do what they can to prevent child-to-mother transmission. Sadly, it’s also true that many opportunities for prevention are missed because most women have not heard of CMV or know how to prevent it, and there is often little antenatal education available on the subject.
To date, the only effective means of preventing congenital CMV is through reducing exposure to the virus whilst the mother is pregnant. Research has shown that rates of maternal infection can be reduced through education regarding sources of infection and improved hygiene (Johnson & Anderson 2014), and there is good evidence to suggest that pregnant women are willing to change their behaviour once they are aware of the risks.
It could be argued, however, that avoiding high-risk activities isn’t enough and that there is also an urgent need for more research into possible vaccines and treatments. In addition to this, there is also the need for a much better understanding of the pathogenesis of infection from the mother via the placenta to the fetus.
That said, in recent years, some significant steps forward have been achieved. These include the diagnosis of primary maternal CMV infection in pregnant women by using the anti-CMV IgG avidity test, and the diagnosis and prognosis of fetal CMV infection by identifying the virus in amniotic fluid (Emery & Lazzarotto 2017).
Whilst the ultimate goal of creating an effective vaccine remains a challenge, the short term goal of raising understanding and awareness through education remains highly achievable.
As more members of the antenatal care team improve their understanding of the dangers of congenital CMV and then pass that knowledge on to the women in their care, reducing the devastating effects of congenital CMV may become a realistic possibility.