Thanks for the great comments on my last post.  One of the commenters mentioned a book called Expecting Better by Emily Oster.  She’s an economist who decided to look into the research behind advice given to pregnant women.  I hadn’t heard of it before, and haven’t read it, but sounds like she got some flack because some people misinterpreted what she wrote about the research on alcohol.  I guess a small amount is thought to be unlikely to cause fetal alcohol syndrome.  They equated it to her saying it’s ok to drink in pregnancy.

Apparently per the book, the research on listeria in pregnancy is pretty strong.  This is the beauty of being pregnant (and of getting feedback on my blog posts).  Now I’m taking the opportunity to look further into it.  As doctors, we generally learn a lot about things that are common (like low back pain and heartburn in pregnancy), as well as things that are very important (knowing what to do about preeclampsia and postpartum hemorrhage).  This other stuff, like the nitty gritty details of food safety in pregnancy, has not been at the top of my priority list.

Now, with my 50-60 hr workweeks, I still don’t have time to be going through all the research articles.  My go-to source is the website UpToDate, which many of us docs subscribe to so that we can quickly look up what the latest research and practice recommendations are on various topics.  It has its limitations, but I generally find it to be a reliable resource.

The FDA website in my last post says that Listeria monocytogenes is a harmful bacterium that can be found in refrigerated, ready-to-eat foods.  It is unusual because it can grow at refrigerator temperatures, where most other foodborne bacteria do not.  The site says that pregnant women are about 10 times more likely to get listeriosis than other healthy adults, and that an estimated 1/7 of all Listeria cases occur in pregnant women.  They cite the CDC for those stats.

UpToDate says that listeriosis occurs most commonly in the third trimester.  Listerial infection in pregnant women can lead to fetal death, premature birth, or infected newborns.  I won’t list all the bad stuff it can cause, but it’s definitely very serious when it occurs.

But getting back to me and my roast beef sandwich.  More recently, at a work lunch where again sandwiches with cold cuts were being served, I did a non-scientific poll of several of my colleagues about whether they’d ever seen listeriosis.  And none of them had.  The fact is, it’s one of those things that’s rare- like none of us had ever even had a co-resident or colleague that we’d heard of with a patient with listeriosis.  Which is why until now, I’ve never really looked into it.  I’m sure none of us can remember to tell every single pregnant patient to avoid cold cuts and unpasteurized foods.  And even if we do, not everyone remembers or follows our advice 100%.  So inevitably a fair number of our patients are eating these “forbidden” foods, and still very rarely get listeriosis.

According to UpToDate, in the US, the incidence of laboratory-confirmed cases of listeriosis between 2009 and 2011 was 0.29 cases per 100,000 persons. In pregnant women, the incidence was 3.0 cases per 100,000 population. The highest incidence was observed in pregnant Hispanic women (7.0 cases per 100,000 population).  According to the FDA site, this is thought to be from these women eating soft cheeses and other traditional foods made from unpasteurized milk.

Like many things in medicine, we doctors have to be cautious about what we recommend to our patients.  You don’t want to tell your patient it’s probably fine to eat cold deli meat, and then have her be that one patient who gets listeriosis.  But when it comes to my own behavior, I’m willing to take some educated risks.


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