The first trimester is also the most crucial stage of your baby’s development so it’s the most important time to sit up and take notice of your diet. Considering that an appointment with a midwife may not come until the end of your first trimester, this leaves many weeks of uncertainty if you don’t research your dietary needs yourself.

Here is the definitive guide as set out by The Food Standards Agency, the independent food advisors working on behalf of the government:

You should be eating at least five varied portions of fruit and vegetables a day in any form. Include plenty of nutritious wholegrain starchy foods such as brown bread, brown pasta, brown rice and sweet potatoes. Protein is important too so include lean meat and poultry, eggs and fish (see below) and pulses such as beans and lentils.

A common early symptom of pregnancy is constipation so include plenty of fibre. Good sources are wholegrain bread, pasta, rice, pulses, fruit and vegetables. You also need to boost your intake of calcium so include milk, cheese, yoghurt and calcium-enriched dairy alternatives.

Though you need to take a daily supplement of 400mcg of folic acid until week 12, you should also include foods containing folate, the natural form of folic acid, contained in green vegetables, brown rice, fortified bread and breakfast cereals.
Pregnant women can easily become deficient in iron so include plenty of iron-rich foods including red meat, pulses, bread, green vegetables and fortified cereals. Drink a glass of juice with iron-rich meals as it will help your body to absorb the iron. There are certain foods that you should avoid when you’re pregnant, because they might make you ill or harm your baby. Avoid cheeses such as Camembert, Brie, chèvre (a type of goats’ cheese) or others that have a similar furry rind. Also avoid any unpasteurised cheeses and blue cheeses, which can contain the bacteria listeria. Avoid all types of pâté, including vegetable as this can also contain listeria. Avoid eating raw eggs and foods containing raw or partially-cooked eggs. Mayonnaise made with pasteurised milk is okay, but check the labels. Make sure you only eat meat that has been thoroughly cooked with no pink areas as raw meat can contain food poisoning bacteria. This is especially important with poultry and products made from minced meat, such as sausages and burgers.

Make sure you don’t have too much vitamin A. This means you should avoid eating liver and liver products such as pâté and avoid taking supplements containing vitamin A or fish liver oils. You can eat most types of fish when you’re pregnant, but you need to avoid eating any large fish including shark, swordfish and marlin because of the levels of mercury they contain. Limit the amount of tuna you eat to no more than two tuna steaks or four medium-size cans of tuna a week. Have no more than two portions of oily fish a week. Oily fish includes fresh tuna (not canned tuna, which doesn’t count as oily fish), mackerel, sardines and trout. Avoid raw shellfish, which can sometimes contain harmful bacteria and viruses. You can eat them if they are thoroughly cooked in a hot meal though.
Your baby may be at higher risk of developing a nut allergy if you, the baby’s father, brothers or sisters have certain allergic conditions such as hayfever, asthma and/or eczema. If your baby is in this higher-risk group, you may wish to avoid eating peanuts and peanut products when you're pregnant and breastfeeding.