Nutrition in the first trimester of pregnancy: what to eat

Why do nausea and aversions to certain foods occur in the first trimester?

Nausea and aversions to certain foods are very common during the first twelve weeks. They are part of the expected changes in the first three months [2], and do not mean that anything is wrong.

During these weeks, human chorionic gonadotropin, the hormone detected by pregnancy tests, rises rapidly. Progesterone also increases, relaxing the muscles of the digestive tract and slowing digestion. As a result, the stomach takes longer to empty, and you feel full after small portions. Your sense of smell also becomes more sensitive. The smell of coffee, hot fish or fried foods may be enough to make you gag. See “Ham and cold cuts in pregnancy”.

Knowing where it comes from can help ease your anxiety. You are not losing your appetite through neglect or harming your baby.

What should you eat to ease nausea in the first trimester?

What usually works best is to spread your food across five or six small meals throughout the day. Nausea often gets worse when your stomach is empty.

On waking, dry foods that are high in carbohydrates and low in fat are often easier to tolerate. Options include toast, rusks, breadsticks, rolled oats, or rice or corn cakes.

Cold or lukewarm dishes can help at lunch and dinner. For example, a lukewarm potato or rice salad, a mild puréed vegetable soup, or boiled chicken with a hard-boiled egg. Steamed white fish is also often well tolerated. Without hot steam, the food smells less and is less likely to put you off.

Ginger is among the options listed by the World Health Organization for relieving nausea in early pregnancy [1]. If you want to take it, ask your pharmacist or doctor, especially if you take medication or are pregnant. There is no need to use capsules or concentrated preparations.

Folic acid, iodine and iron in the first weeks

Your energy needs barely change at first, but some nutrients matter even before conception. The embryo’s neural tube, from which the brain and spinal cord develop, closes during the first weeks.

Folic acid (vitamin B9) is the key nutrient in the first trimester. Taking it in time reduces the risk of neural tube defects, such as spina bifida. Your midwife or gynaecologist recommends your folic acid supplement; your dietitian-nutritionist helps you with the food you eat alongside it [1]. During pregnancy, 600 µg per day of dietary folate equivalents is recommended [3].

Spinach, chard, lentils and nuts are rich in folates. Even so, food alone does not replace the supplement. If you are still trying to conceive, the guide to eating before pregnancy explains how to prepare.

Iodine is used to make thyroid hormones, which are essential for your baby’s brain development. Sociedad Española de Ginecología y Obstetricia recommends using iodized salt and supplementing with potassium iodide during pregnancy [2]. Other Spanish guidelines reserve supplementation for people who do not get enough iodine from their diet—that is, three servings of dairy a day and iodized salt [4]. The adequate iodine intake during pregnancy is 200 µg per day [5]. If you need a supplement, your doctor or dietitian-nutritionist will prescribe it.

Iron, calcium and vitamin D are obtained mainly from food. For iron, choose meat, fish, eggs and legumes, alongside foods containing vitamin C. For calcium, choose dairy products or a calcium-fortified plant-based drink with at least 3% protein, preferably soy (an allergen). For vitamin D, take walks outdoors. Your doctor or dietitian-nutritionist will prescribe an iron supplement based on your blood test results. The WHO recommends it for all pregnant women; in Spain, it is adjusted case by case [2]. If you already have anaemia, your doctor will prescribe iron treatment. Diet alone does not correct anaemia.

If you can barely eat because of vomiting or nausea

This is one of the situations that causes the most anxiety, and one of the issues we hear about most often in consultations during these weeks. You open the fridge, feel nauseated, and can barely tolerate a few bites all day. It is understandable to worry that your baby is not getting what they need. Eating little for a few days or weeks does not usually put your baby at risk in early pregnancy.

During these weeks, the embryo is very small, and so are its needs. If for a while you eat little more than toast, boiled potato, broth and apple, your baby will usually continue to develop normally . On bad days, hydration comes first.

Dehydration from repeated vomiting is a real risk. Avoid drinking whole glasses at once, because liquid in an empty stomach can trigger vomiting. Take small sips every ten to fifteen minutes. You can try cool water, water with a few drops of lemon, mild chamomile, lemon balm or lemon verbena infusions, or oral rehydration solution if you tolerate it better. If one day you can only manage mashed potato or yoghurt, eat that without forcing yourself to finish the plate or feeling guilty. For most women, nausea starts to ease as they enter the second trimester.

If you are vomiting so much that you cannot keep even liquids down, do not wait. Further below, you can find out when to see a doctor.

Which foods should you avoid from the start?

During pregnancy, the immune system adapts to tolerate the fetus. This makes you more vulnerable to some foodborne infections, which can cross the placenta. Agencia Española de Seguridad Alimentaria y Nutrición explains how to avoid them [6].

Listeriosis, caused by the bacterium Listeria monocytogenes, can cause miscarriage or premature birth. To prevent it, avoid raw milk and unpasteurized soft or blue cheeses, refrigerated pâtés, and prepared dishes that have been open for several days. The cheese label must state that it is made with pasteurized milk.

Toxoplasmosis and salmonellosis can be prevented by cooking meat, poultry, fish and eggs thoroughly, until the yolk is firm, and washing raw fruit and vegetables well. If you are not sure whether you are immune to toxoplasmosis, avoid raw cured sausages such as chorizo, salchichón or cured ham. They can be eaten if cooked to 70 °C at the centre of the food [6].

Large predatory fish accumulate methylmercury, a metal that is toxic to the developing baby’s nervous system. For this reason, avoid swordfish or emperor fish, bluefin tuna, shark (school shark, shortfin mako, blue shark) and pike [6]. There is no safe amount of alcohol, so it is best not to drink any. Caffeine does not pose a risk to the fetus up to 200 mg per day from all sources combined [7]. That is roughly two coffees; energy drinks and cola drinks count too.

What mistakes do we see in consultations?

We hear these questions almost every week, and they are easy to address.

• Eating for two from day one. In the first trimester, your energy needs barely change, and the Spanish prenatal care guideline only adds extra energy from the second trimester onwards [2]. For now, tolerating food and staying hydrated matter more.
• Starting folic acid once you find out you are pregnant. It is recommended from at least one month before conception and throughout the first three months [2]. If you were not taking it, mention this at your first appointment.
• Taking iron or multivitamins on your own, “just in case.” Take them when prescribed by your doctor or midwife, based on your blood test results.
• Avoiding all cheese and yoghurt because of listeria. Pasteurized dairy products are safe to eat. You need to avoid raw milk and unpasteurized soft or blue cheeses.
• Giving up fish because of mercury. Only large fish need to be avoided. Properly cooked white fish can still be part of your meals.

What changes when you move into the second trimester?

After the first trimester, your energy often returns, and the period of greatest growth for the baby begins. Your energy and nutrient needs increase gradually.

For guidance on planning meals in the second and third trimesters, and supporting healthy weight gain without restrictive diets, see the complete guide to eating during pregnancy. See “How much weight to gain in pregnancy based on your starting weight”.