Your guide to first trimester nutrition

By Annemarie Aburrow RD

The first trimester covers your pregnancy right from the time of conception when the first cells are formed, up until the end of week 12. It's an important trimester in terms of your baby's development – organs take shape, your baby starts moving and muscles form. Your 12 week old baby emerges from this trimester as a fully-formed foetus, about the size of a peach, ready to enter the second trimester.

Tips for a healthy diet

A healthy diet is really important throughout the whole of pregnancy. The Eatwell Guide shows the right proportions of foods which make up a healthy diet. Following these tips will will help you to eat healthily:

Nutritional requirements in the first trimester

You don't need extra energy (calories) until the third trimester. You will likely only gain a very small amount of weight or none at all in the first trimester. Most of your pregnancy weight will be put on in the second trimester, so there's plenty of time for weight gain! Your body has a small increased requirement for protein (found in foods like meat, fish, nuts, beans, pulses and cheese). However dietary surveys show that most of us eat more than our requirements anyway – average intake for women aged 19-49 is 61g per day (pregnancy requirement is 57g).

There are increased requirements for folic acid and vitamin D, and supplements for these vitamins are required. Vitamin A requirements are slightly raised, but be sure to avoid supplements containing vitamin A and liver/liver products as they contain a potentially toxic form of vitamin A. Safe forms of vitamin A are found in fruits, vegetables and dairy products.

Supplement needs

We need to take folic acid (400 micrograms per day) and vitamin D (10 micrograms per day) during the first trimester. Taking folic acid supplements during pre-conception and for the first 12 weeks has been shown to help prevent neural tube defects, e.g. spina bifida. If you didn't take folic acid pre-conception, try not to worry – just start taking it as soon as you find our you're expecting.

Vitamin D is important for bone health, and helps us absorb calcium from our diet. Most women get the majority of their vitamin D needs from the action of sunlight on skin, but requirements are higher during pregnancy, so supplements are required. You can either take single vitamin supplements of folic acid and vitamin D (check the label to ensure you're getting the right dose), or you can take pregnancy multi-vitamin supplements or Healthy Start Vitamins. Don't take regular vitamins or cod liver oil because they contain high doses of vitamin A which could be harmful for your baby.

Which prenatal vitamins

If you already consume a healthy, well-balanced diet, all you need is the basic formula that contains the recommended 400mcg of folic acid and 10mcg of vitamin D. You can get it from Boots or Holland & Barrett. Also, it’s a great option if you’re on a budget!

For those of you who feel like you could use some additional help in the nutrition department, go for a more complete supplement such as UK’s bestselling prenatal formula Pregnacare Plus Omega-3. It contains a combination of 19 vitamins and minerals, including 400mcg of folic acid and 10mcg of vitamin D, plus fish oil capsules.

Another option is New Chapter Perfect Prenatal. It’s an organic, whole food supplement rich in high quality nutrients, including multivitamin complex and probiotic blend. Although quite expensive, the supplement is very highly rated on the other side of the Atlantic and you can buy it in the UK from Amazon or small online vitamin retailers.

Foods to limit / avoid

Coping with morning sickness

Morning sickness is common in pregnancy, affecting around 50% of women. This nausea and vomiting usually improves by the end of the first trimester, leaving you to enjoy your pregnancy 'bloom' during the second trimester. Try not to worry if you can't eat much on some days. Remember that you don't need to gain any weight this trimester. Try to keep your fluids up and eat when you feel you can. If you affected by morning sickness, you may find these tips helpful:

Other considerations

Physical activity

It's safe to continue your usual exercise during pregnancy. If you're not active, now is the time to start something regular. Build up gradually, aiming for 30 mins at least 5 days a week. Regular physical activity will not only keep your weight in check, but may help you have an easier pregnancy and labour.

Wash fruits and veggies well

Unwashed fruits, veggies and salads could contain toxoplasmosis, a parasite which could potentially cause miscarriage and birth defects.


There are many theories for why women get cravings, but there is no firm evidence as to why they occur. If your cravings involve unhealthy foods, try not to worry as cravings are usually only temporary.


You may experience this, although it can be worse during the second and third trimesters. Eating small, frequent meals, sitting up at the table and not eating too close to bedtime may help ease heartburn.

You might also like:

Your guide to second trimester nutrition

Your guide to third trimester nutrition

A guide to your nutritional requirements in pregnancy

Digestive problems during pregnancy

“Pass the sick bag”: Eating your way through Hyperemesis Gravidarum

The sunshine vitamin: Vitamin D in pregnancy

The role of folic acid in pregnancy and pre-conception

Alcohol consumption during the first trimester of pregnancy

Healthy diet for vegan pregnancy

Healthy nutrition tips for the vegetarian mothers-to-be

Prenatal vitamins explained

Foods to avoid in pregnancy


Your New Pregnancy Bible

The experts' guide to pregnancy and early parenthood - by Dr Anne Deans


Your guide to second trimester nutrition

Your guide to third trimester nutrition

Bulimia, fertility and pregnancy

Caffeine in pregnancy: How much is too much?

“Pass the sick bag”: Eating your way through Hyperemesis Gravidarum

The role of probiotics in breastfeeding

Digestive problems during pregnancy

Calcium during pregnancy – what you need to know

Your guide to first trimester nutrition

Trying to Conceive? Foods you should avoid

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