Safe to wear heated thermal garments while pregnant?
March 3, 2021 1:37 PM   Subscribe

I'm going to be working at an outdoor job site for a few days. The employees will be given "thin electric heated thermals" to wear- basically battery operated long johns. I'm 17 weeks pregnant but my workplace doesn't know. Is this safe? Can I make it safer?

We'll all have to be outside for about 8 hours, and every other person will be wearing the heated thermals, so if my cold tolerance is much less than everyone else's, that's a problem. I won't have leeway to leave the group, and there won't really be anywhere to go to warm up.

I have to wear a specific uniform for work - basically a warm fall outfit with layers - not terrible but not warm enough to be outside all day in the winter. I cannot add extra layers over it as all employees need to match.

So I pretty much have to wear the thermals but I'm a bit worried. My plan was:

Wear another layer against my skin below them
Wear wool and silk etc to stay extra warm
Be very familiar with how to turn the thermals off and take heat breaks
Drink lots of water
Pad my belly area with extra fabric so the heat is buffered over that area

Anything else I can do? Anything specific I should be aware of?
posted by anonymous to Science & Nature (9 answers total)
This is something I would talk to your OB about.
posted by DoubleLune at 1:52 PM on March 3 [3 favorites]

I don't think the concern would be heat, but would be electromagnetic fields from the heating elements.

I googled "electric blankets while pregnant" to get comparable, but couldn't find any results that I would trust.

Given that, I'd go with DoubleLune and talk to your OB.
posted by Winnie the Proust at 2:11 PM on March 3

I feel like I should expand on my answer - as someone who has been pregnant, and who sometimes works outdoors in extreme temperatures, I, personally, would not be comfortable wearing heated thermals because a) the localized heat could in theory get above what is recommended for pregnancy and b) if they operate like electric blankets, there's theoretically some issue with electromagnetic waves that could harm the fetus. If it were me, and I hadn't told work yet, I would call my OB and discuss the thermals. I was potentially in a situation of having to be in extreme conditions on a barge for a day or two while ~12 weeks pregnant (I told work at 14 weeks), and while I ended up not having to go, I discussed it with my OB at the time.

In your situation, if there's some reason you can't talk to/don't trust your OB, I would not wear the thermals, but I would wear lots of layers under your uniform, heat packs in your shoes/boots and gloves, have a warm, sugary, uncaffeinated beverage at hand to keep your core temperature up, and take lots of breaks in a warm area.
posted by DoubleLune at 2:11 PM on March 3 [4 favorites]

A battery-powered set of electrified thermals won't give off any emf as it's going to be DC powered. Additionally I don't think there's really any meaningful risk in terms of emf from AC electric blankets either, although overheating is of course a possible issue.

Assuming that the electric thermals work as intended and keep you comfortably warm I'd be more concerned about making sure you have a backup battery or two as the heated base layers I've seen might only last a couple hours on the highest setting.
posted by GuyZero at 2:31 PM on March 3 [8 favorites]

My doctor explained to me the real danger is any systematic overheating. So he was actually ok with me taking hot baths, going to hot springs, etc. as long as I was cognizant of body temperature and took breaks as needed. Your body has really good insulation between the outside of your body and the baby. I don't think I would worry about any spot insulation, if you feel warm like you have on a good coat, that is good. If you feel hot, stuffy, sweaty, beginning to flush, etc. it is too hot and you need to be able to turn it off or get out of it ASAP.

Talk to your doctor though, that is the only real answer. They all have different levels of experience and comfort in these matters and hopefully they have a good read on your general health and can make appropriate recommendations.
posted by stormygrey at 2:42 PM on March 3 [10 favorites]

Can you wear some stick-on heat packs/patches on your extremities instead of activating the thermals?
posted by trig at 3:07 PM on March 3

I can't speak to the pregnancy aspect but you might check with coworkers that have used the garments before how much heat they actually put out. Unless they have a seriously beefy battery or you're swapping batteries frequently, the amount of heat that they put out is pretty small.
posted by Candleman at 3:42 PM on March 3

You will get a lot more electromagnetic exposure from living in a house than from wearing a battery-powered heater. Even if not, I am not aware of any credible evidence that electromagnetism is harmful to any living thing under any circumstances. It seems very unlikely, because we're surrounded by various fields all the time.
As for heat, you'll know if you're too hot. A baby is extremely well protected, and your body will not casually allow it to come to harm. I can't imagine that you could get so overheated that the baby would suffer without being extremely uncomfortable yourself.
As a student I wondered if being in a hot bath would raise my body temperature, so I sat in the hottest bath I could tolerate, with a thermometer in my mouth. After an hour there was no change.
I really don't think either of these things are worth worrying about.
posted by AugustusCrunch at 9:54 PM on March 3 [3 favorites]

There's a section in MeFi fave Expecting Better about this. Here's the salient paragraph:

It's probably important to note that the real concern is about an increase in body temperature to above 101F degrees or so. [Some notes about typical hot tub and Bikram yoga temperature being 105F, and cooler versions of about 85F or 90F are fine.] In addition, the neural tube defect concern is limited to the first trimester; by the end of that period, neural tube formation is complete.

According to a couple of Amazon listings for thermal underwear, the low setting is about 95-100F and the high setting is about 135F.

Given that the main concerns about overheating are in the first trimester, which you are well past, you're probably fine, especially if you keep them on the lowest setting and plan to take breaks if you feel overheated. But obviously, double check with your OB! (I am not a doctor, just a fellow pregnant person who likes to research things.)
posted by natabat at 1:53 PM on March 4

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