When you’re pregnant, the hormonal changes your body goes through affects your immune system and increases your susceptibility to certain infections. The foods that you are often told to avoid while pregnant have to do with the fact that the risk of contamination is higher in those foods, particularly with Listeria or Salmonella. The foods themselves are not necessarily harmful—but because of improper preparation or storage, they have a higher likelihood of contamination.
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What is Listeria and how does it affect you while pregnant?
Listeria is a bacteria that causes infection if ingested. In healthy and young people, a listeria infection typically causes food poisoning symptoms, like nausea, diarrhea and fever. But for pregnant people (and the elderly or those with weakened immune systems) Listeria can be serious, and for the fetus, it can be fatal.
How is Listeriosis treated?
In the event of infection, early detection and a course of antibiotics can significantly reduce the negative outcomes to the fetus.
How common are Listeria infections?
These infections happen about 20 times more in pregnancy than in the general public. The incidence of listeriosis in pregnancy has been reported as 12 cases per 100,000 pregnancies. The Centers for Disease Control and Prevention (CDC) estimated that there were about 800 cases of listeriosis in pregnancy in the US in 2007. In Canada, there are approximately 134 cases in the general population per year. The majority of Listeriosis (caused by Listeria) outbreaks have been linked to contaminated deli meats, soft cheeses and unpasteurized dairy products. When food is properly prepared and stored, the risk of being infected with Listeria is fairly low.
What is salmonella and how does it affect you while pregnant?
Salmonella is a bacteria that causes infection in the intestinal tract. This can cause severe dehydration and diarrhea in the pregnant person and the infection can be passed on to the fetus, causing the same symptoms to be present at birth as well as sepsis or meningitis.
How is a Salmonella infection treated?
Much like Listeriosis, early detection and a course of antibiotics can significantly reduce the negative outcomes to the fetus.
How common are Salmonella infections?
Salmonella contamination is more common in raw or unpasteurized eggs and foods that contain them, like mayonnaise, salad dressings, cookie dough and even some ice creams. The chance of an egg being contaminated with salmonella ranges from one in 30,000 to one in 10,000.
How can I avoid bacterial infections?
You don’t necessarily need to avoid all soft cheeses or deli meats—but do make sure to get them from a reputable source, consume them in a timely manner (ideally within two days) and keep them refrigerated. Ready-to-eat foods that are stored in refrigeration for long periods also have a higher risk of contamination (in Canada this includes bagged salads). The same can be said for seafood: a gas-station or supermarket is not a place to buy sushi. If you’re craving salmon sashimi, go to a reputable sushi restaurant that gets frequent fresh deliveries, and consume it soon after preparation. To reduce the risk of food poisoning, refrigerate leftovers within two hours and avoid eating leftovers that are older than three days.
Foods to avoid while pregnant
The risk of food poisoning is very low if you’re eating high-quality food from trusted sources that has been prepared and stored properly. If you do want to enjoy that oven-roasted turkey sandwich, there are ways to minimize the risks associated with consuming deli meat. But, if you’re erring on the side of caution, here’s a list of what to avoid.
- Raw fish (and fish high in mercury like tuna and swordfish)
- Deli meats
- Raw or undercooked eggs (including foods that include them like mayonnaise and cookie dough)
- Soft cheeses
- Unpasteurized dairy products
Should I avoid all alcohol during pregnancy?
It has been well established that alcohol can negatively impact a growing fetus during pregnancy and increase the risk of Fetal Alcohol Spectrum Disorder (FASD). Alcohol is a known reproductive toxin and teratogen, meaning it can easily cross the placenta and cause abnormalities during the development of the embryo and fetus. When a pregnant person drinks, alcohol can accumulate in the amniotic fluid, prolonging the effect for the fetus. A fetus also doesn’t have strong enough liver function to process alcohol the way a grown adult does.
Apart from the developmental impacts, there is also a strong association between maternal drinking during pregnancy and miscarriage. Most studies found miscarriage to be linked to having two to four drinks per week. For example, in a cohort study of pregnant women in San Francisco, it was reported that women who drank four or more drinks per week, and those who consumed spirits, had two times the risk of miscarriage compared to women who abstained. As well, a greater risk was found when drinking occurred in early pregnancy (less than 10 weeks).
There is no amount of alcohol exposure during pregnancy that is established as safe, so it’s best to just avoid alcohol while pregnant.