Maybe, but you should certainly avoid deli meats for the listeria (If you follow through that link and read you’ll know why). This isn’t an abstract risk, Listeria out breaks are happening all the time (just ask a Canuck how their year went). Let’s not go down that road and get back to the nitrates.
Nitrates can convert to nitrites in your gut if you have high pH. If you’re normal almost all of the nitrates are not converted or absorbed into your body. Now, there’s no good way to tell if you have a high pH gut so you’re going to have to assume that you do. So, these converted nitrites get absorbed and do one of two things: they form N-nitrosamines which are cancer causing agents, or they latch on to hemaglobin to form methemoglobinemia, a condition that makes it so your blood can’t carry oxygen around. When you’re pregnant, you’re worried about the second issue.
How that lack of oxygen leads to the effects nitrates are known for is unknown. Perhaps it through a different pathway. Regardless, from animal studies, we know that nitrate, nitrite, and N-nitroso compounds cross the placenta. Methemoglobin probably can’t after the 4th month or so but this doesn’t ease the problem of low oxygen delivery to the placenta.
The most consistent finding from nitrates is that of spontaneous abortion. This occurs in some studies at as little as 2.5mg/kg in not in others and seems to be about the break point. A pregnant rat is roughly 200 g or little under so that’s about 0.5 mg/day for a rat. To convert to an equivalent human dose toxicologists (good ones anyway) use a mg/m^2 basis. So 2.5 mg/kg is about 15 mg/m^2 in a rat; 15 mg/m^2 in a human is about 24 mg/day for an average person. The amount of nitrates in meats has gone down quite a bit over the past couple years and meats have between 6-20 mg/kg of nitrate so you’d have to eat over a kg of a highly perserved meat (like salami for instance) to get close to this.
You can see where I’m going with this: if you eat a small amount of food with nitrates once in a while you’re fine but it’s a good idea to generally avoid them. Interestingly enough, most of your nitrate intake comes from really healthy things like dark green veggies that you need to keep eating especially while pregnant (although a daily spinach salad may be overboard). All things in moderation. Oh, one more thing. If you eat a lot of vitamin C with the nitrates, it reduces the amount that’s converted to nitrites.
There is a better way.
Don’t want high nitrates or listeria? Do what I do: make your own! Last year I posted on my favorite breakfast sausage recipie, and you can make your own small hams and bacon and use very little or no nitrates. An excellent source is Charcuterie (I’ve got their breakfast sausage beat, though). The thing about making your own sausage is that it tastes much, much better, you’ll enjoy the product even more (and likely the process too), but best of all, you’ll end up eating less because you recognize the work that went into it and will view these cured meats as the treats they are.
Thanks to Liz for asking the question.