What not to eat during pregnancy (and what you can eat)

Which foods should you avoid during pregnancy, and why?

The foods to avoid during pregnancy relate to four specific risks: the bacterium Listeria monocytogenes, the parasite Toxoplasma gondii, and mercury accumulated by large fish. The fourth risk comes from substances that harm the developing baby, such as alcohol or too much caffeine [1]. Most can be avoided by choosing foods carefully and following good kitchen hygiene [1]. See “Listeria in pregnancy”.

Avoiding these foods does not make your diet less nutritious, because each has a safe alternative with the same nutritional value. To plan your meals over the nine months, see the pregnancy diet. If you are in the first weeks, the guide to eating during the first trimester can help with nausea and appetite.

Why can raw meat and cured meats transmit toxoplasmosis?

Toxoplasma is a parasite found in raw or undercooked meat from infected animals. It is also found in soil and water contaminated by cat faeces. If you become infected for the first time during pregnancy, it can cross the placenta. It can then cause a miscarriage or damage to the baby’s brain, eyes and other organs [1].

The Spanish Society of Gynaecology and Obstetrics does not recommend testing all pregnant women for toxoplasma [3]. If you are not sure that you are immune, avoid raw or undercooked meat and eggs, and cured meats that have not been cured for long [3]. Raw cured meats, such as chorizo, salchichón or cured ham, can be eaten when cooked. The guideline is to reach 70 °C at the centre of the food, as in a thoroughly baked pizza or croquettes [1].

For meat and poultry [3], the guideline is to reach 70 °C at the centre of the food [1]. Check this with a kitchen thermometer.

Which dairy products, cold cuts and pâtés may contain listeria?

Listeria is a bacterium that can multiply at refrigerator temperatures. In the mother, it may go unnoticed or feel like a mild bout of flu. Infection is uncommon, but it can cause miscarriage, premature birth, stillbirth, or meningitis or sepsis in the baby [1].

According to the Spanish Agency for Food Safety and Nutrition, the foods at greatest risk are refrigerated ready-to-eat foods [1]. These include raw milk and cheeses made from unpasteurised milk, such as brie, camembert, feta or artisanal blue cheeses. They also include industrially sliced or grated cheeses, refrigerated pâtés, sliced cold cuts and packaged sandwiches [1]. Smoked fish, such as salmon, may also contain listeria [1]. Freezing it does not help, because cold slows the bacterium down but does not kill it. See “Ham and cold cuts in pregnancy”.

The alternative is simple. Check that the cheese label says “made with pasteurised milk”. Pasteurised hard and semi-hard cheeses, mozzarella and pasteurised ricotta are suitable. Cooked ham and turkey are best heated in a hot dish rather than eaten cold in slices.

Which fish contain too much mercury during pregnancy?

Fish is an excellent food during pregnancy. It provides protein, iodine and omega-3, including DHA, which plays a role in the baby’s neurological and visual development [3]. The problem is certain large, long-lived species, which accumulate methylmercury along the food chain [4]. This metal crosses the placenta and can affect the baby’s nervous system development [4].

For this reason, if you are pregnant, breastfeeding or trying to become pregnant, it is best to avoid four species [4]: swordfish or emperor fish, Atlantic bluefin tuna (Thunnus thynnus), shark (school shark, blue shark, shortfin mako) and pike.

The rest of the fish can remain on your menu: at least three servings a week, prioritising oily fish and varying the species [1]. Hake, cod, sole, sea bream, sea bass, squid, sardines and salmon are good options. Canned light tuna comes from smaller species, such as yellowfin or skipjack. It contains considerably less mercury than bluefin tuna and can be eaten in moderation.

Can you drink alcohol during pregnancy?

No. Alcohol crosses the placenta and reaches the baby’s bloodstream at concentrations similar to those in the mother. The baby’s liver cannot yet eliminate it, so exposure continues while the organs are forming.

The Spanish Society of Gynaecology and Obstetrics recommends avoiding alcoholic drinks throughout pregnancy [3]. There is no amount of alcohol that is safe for health (WHO): the less, the better; and none during pregnancy, breastfeeding, childhood, if you are going to drive, or if your medication does not allow it. Ideally, stop drinking as soon as you start trying to conceive. Alcohol during pregnancy causes fetal alcohol spectrum disorder. This ranges from low birth weight and birth defects to lifelong behavioural and learning difficulties.

At celebrations and meals with friends, sparkling water with lemon or chilled herbal tea are safe options.

How much caffeine can you have during pregnancy?

Up to 200 mg of caffeine per day, counting all sources. This is the figure set by the European Food Safety Authority, which concludes that this amount does not pose a risk to the fetus [2]. During pregnancy, the body eliminates caffeine more slowly. It also crosses the placenta, and the baby’s liver cannot process it quickly. High caffeine intake has been associated with a greater risk of low birth weight and restricted growth [2].

Some other international recommendations set a slightly higher limit and advise people who consume more than 300 mg a day to cut down [5]. We follow the more cautious European limit.

In practice, 200 mg is roughly equivalent to two coffees a day. But tea, cola drinks, energy drinks and chocolate also add to your intake. If you do not want to keep track, decaffeinated coffee is the easiest option.

How to wash raw vegetables and prevent contamination in the kitchen

Raw fruit and vegetables are essential for their fibre, vitamins and minerals. However, their surfaces may carry toxoplasma from soil or bacteria such as Listeria or Escherichia coli. Wash them under running tap water and scrub those with firm skins [1].

Leafy vegetables eaten raw and fruit with the skin on also need to be disinfected. Use bleach whose label states that it is suitable for disinfecting drinking water. Add about four drops per litre of water and leave the produce submerged for at least ten minutes [1]. Then rinse it thoroughly with drinking water.

The rest of the prevention is about avoiding cross-contamination, which means germs from a raw food passing to another food that is ready to eat [1].

If you eat out

At a restaurant, you cannot control the kitchen, but you can choose what you order. Ask for meat and fish to be thoroughly cooked, and avoid dishes that are medium-rare, marinated or served as carpaccio. If you do not know how the salad was washed, choose cooked, roasted or steamed vegetables. For dessert, peeled fruit, yoghurt or thoroughly baked pastries are safe options. Homemade mousses, tiramisu and unset meringue contain raw egg.

Which questions come up most often in consultations?

These three come up almost every week, often at the first appointment.

“If I freeze it, I can eat sushi.” Freezing fish protects against anisakis, a parasite found in raw fish. Listeria, on the other hand, survives freezing [1]. During pregnancy, avoid raw fish even if it has been frozen.

“Alcohol-free beer does not count.” Conventional alcohol-free beers may contain a small amount of alcohol. If you fancy one, look for those labelled “0.0%”.

“I ate it before I knew I was pregnant.” This happens very often, and there is no point in worrying now. Mention it to your midwife at your next appointment and follow these guidelines from today onwards.