Thread by @VikiLovesFACS

A lot of people have been asking if #fever as a side-effect of #COVID19 #vaccination is something we should worry about in #pregnancy. So let’s talk about that… 1/

Fever in pregnancy is potentially a concern because a having temperature of more than 39 C (102 F), lasting for at least 24 hours, during the first trimester is associated with an increased risk of certain birth defects. 2/

I like this review, even though it’s a bit old now, because it does a good job of integrating the animal and human data in this area. 3/

tandfonline.com/doi/pdf/10.108…

Fever is a commonly-reported side-effect of vaccination – whether you are pregnant or not. 4/

cdc.gov/vaccines/acip/…

So, should we be worried about vaccination-associated fever in the context of pregnancy? 5/

I think it’s first important to be clear that these are self-reported fevers. So they will not all meet the criteria for increased risk: being higher than 39 C (102 F) and lasting for 24 hours. 6/

Nonetheless, some of them may, and I think that’s a possibility we should take seriously. Luckily, there are ways we can mitigate against these potential bad effects of fever… 7/

(This, by the way, also applies to – indeed was discovered in the context of – fevers associated with infectious diseases. So all the information below applies equally if you have a fever because of an infection.) 8/

We know that taking folic acid around the time of conception and in the first trimester of pregnancy reduces the risk of certain birth defects – this is why we recommend that everyone take it when they are trying to conceive, or pregnant. 9/

But taking folic acid *also* reduces the risk of these problems specifically associated with fever by about a third. 10/

sciencedirect.com/science/articl…

We also know that paracetamol (Tylenol) can bring down a fever. In this study, using it to treat a fever in the first trimester reduced the risk of birth defects back to normal levels. 11/

journals.lww.com/greenjournal/F…

Paracetamol (Tylenol) is safe in pregnancy and does not prevent COVID19 vaccines from working. For this reason @acog recommends taking paracetamol to treat any post-vaccination fever if you are pregnant. 12/

acog.org/-/media/projec…

So, although most vaccination-related fevers will not be high or long-lasting enough to be of concern, it is still likely to be worth mitigating any potential effects of fever when vaccinating in the first trimester, just in case. 13/

We can do this by recommending folic acid (which hopefully people will be taking anyway!) and treating any fever that may occur with paracetamol (Tylenol). 14/14