cmv: the fallout

At the beginning of the diagnostic process, it’s common nature to want to order of barrage of tests and studies, to amass as much information as possible and then sift through it all to find that one golden diagnosis that will put all the pieces together.  In med school, we learn to try resist that temptation.  Not only is it incredibly expensive (maybe why health care in the U.S. costs over 2.5 times the amount it does in other developed nations), but it can also muddle more than clarify the means of health care delivery.  It’s why we screen for breast cancer in women without certain predisposing conditions with mammograms rather than MRIs, the latter being the arguably more sensitive study.  Too frequently the MRI will come back with incidental findings or false positives that will require follow-up, often more invasive testing (like a biopsy) and, ultimately, a lot of stress for patient, family, and provider.  When I order a study, I try to remind myself, “What will I do with the results?  And will it change my management?”

As a patient, I allow myself the luxury of not thinking like a care provider, and I’m afraid a become a pretty paranoid individual, going way overboard with diagnostic tests and procedures as a means of reassurance.  In the fall, I was mostly convinced that I wasn’t a carrier of Tay-Sachs, but I asked to be tested so I could really put any sense of worry out of my head…and look what it got me.  You’d think I’d learn, but when we found out our babysitter had parvovirus, I though, might as well get tested for both parvo and CMV, since they’re both ubiquitous infections in the pediatric population.  Chances are, I’d be in the 50-80% of women already exposed to CMV and I could just put the matter to bed.

You already know where this story is going.  My serology testing for parvo confirmed that I was IgG positive, meaning that I had already a previous exposure without any signs of an acute infection, and I am likely immune.  Score!  CMV, not so much.  I had both the presence of IgG and IgM antibodies in my blood.  This result is frustrating.  IgM signals an acute infection, but it can remain positive up to 12 months or more after the initial infection.  It can also spike again during re-exposure or reactivation, although the risks to the fetus in such a scenario are incredibly low.  Unfortunately the presence of IgG doesn’t help us out because, with this particular virus, it can rise quite quickly after the initial exposure.

I was disappointed and concerned with the results but, given the fact that I had a normal anatomy scan at 20 weeks and the fetus was growing appropriately for gestational age, I was able to talk myself down off the ledge.  Even an acute CMV infection does not necessarily mean that the fetus is affected.  If I was infected during the first trimester, the risk of transmission is quite low, but the consequences are great (calcifications on the brain, microcephaly, intrauterine growth restriction are some of the common findings)–my normal 20-week ultrasound is reassuring.  If I was infected late in the pregnancy, the transmission risk is much higher (some estimate as much as 40%), but the possible effects on the fetus are less severe, with many being entirely asymptomatic and hearing loss often being the most significant deficit.  I spoke at some length with one of the neonatologists with whom I’m working who specializes in virology.  She validated my frustrations.  In the end, there is so much we don’t know about CMV and, since there is very little we can do to prevent exposure (though pediatricians and daycare workers are certainly at higher risk) and no proven method of treatment, it’s not standard prenatal testing.  I was happy to let the issue rest for now, though accepting that our second born would need to be tested at birth and followed for a couple years to test of hearing impairment mostly.

The midwives I see are normally very low-key, but they did decide to consult Infectious Disease (ID) with my case, and it was recommended that I be followed by both ID and Maternal-Fetal Medicine (MFM).  It’s likely overkill, but I’m already down this road.  Today I met with MFM and had an ultrasound to check for any findings consistent with congenital CMV.  What a treat!  Not only does our daughter look normal (in a good way!) and healthy and growing appropriately, but the technician also noted that she looked to have a full head of hair, taking after her sister and everyone else on her father’s side!  Estimated current weight is 4 lb 9 oz, more than most of the babies I’m caring for in the NICU–we normally throw up a celebratory sign on the crib or isolette when a baby hits the 4-pound mark!

One of the MFM docs recommended an IgG avidity test, which could give us information about whether my infection is acute or likely from more than four months ago.  I declined.  I’m content with my level of reassurance at this point, and I’m not sure what the results of an avidity test would do to this precarious happy place I’m in currently.  If the tests showed low CMV IgG avidity (indicating likely acute infection), I would worry about the high transmission rate of CMV in the third trimester.  If there was high CMV IgG (meaning the infection was likely over four months ago), I would be concerned about the more concerning potential effects of a first trimester infection.  I’m finally trying to discern ahead of time how I would deal with the results of a given study, and act accordingly.  And, regardless, the results would not change management.

I’ll try to focus instead on this little healthy nugget I have at home, who apparently delights in stacking her Chex cereal on top of her sippy cup.  Fingers crossed she’s spared of this awful cold John and I have been hacking through!  Can it please be Spring?