How Can I Measure My CMV Risk?

Hi Emily! Somewhat of a niche question here, but hopefully a solid exercise in evaluating risk. My wife and I (same-sex couple) have a 21-month-old and are planning for our second child. Originally we were set on having me carry the second baby, as my wife carried our daughter, who was born via C-section. However, after reading your newsletter on CMV, we’re concerned about that plan, as I’m CMV-negative. How do we evaluate the risk of being pregnant and CMV-negative with a toddler at home vs. the potential risks with a second IVF pregnancy after C-section? Obviously most couples don’t have the luxury of choosing who becomes pregnant, but I almost wish this decision were made for us.
—Conflicted because of… too much data?

I’m going to answer it. But first, let me say this question is an extremely good example of structured decision-making. In yesterday’s post I talked about the importance of recognizing that no option is risk-free; here, you’re clearly articulating a tradeoff between two (very slightly risky) options and being clear on them. So, excellent.

To answer: luckily, both sides of this risk coin are low-risk. Pregnancy after a single C-section has a slightly elevated risk of placental complications, but only slightly; these risks increase more substantially after multiple surgeries.

In terms of CMV, we can draw some numbers out of the earlier post. If you haven’t had primary CMV before, the estimated risk of transmission is about 2% per year, so let’s say 2% over the course of the pregnancy. The risk of passing the virus on is then about 40% if you did have primary infection, so the overall risk is about 0.8%. I will note that if your wife is a carrier of CMV, she would also have a risk of transmitting to the fetus; also around 1%. In either case, there is some small risk here. In your case, you could significantly mitigate this risk by being careful about saliva transmission with your daughter (no mouth kissing, no sharing food).

Bottom line: From a risk standpoint, these are both in line with the kind of risks you take every day without thinking about it. So this decision should likely be made based more on your family preferences.