Most people recognise that during pregnancy, the mother’s habits can affect the health of her offspring.  Thus it is important that expecting mums know what to eat and what to avoid when pregnant.

Our advice is to always follow the advice of your local healthcare team that you will engage with during pregnancy.  Let them guide you as to what your nutrition goals might be, then let us know so that we can support you. That said, we always refer to the evidence available and advise to be wary of people selling you supplements that aren’t required.

Good nutrition during pregnancy

Pregancy is a period of anabolism, or growth.  Women are encouraged to eat more when pregnant than they typically do, and recognise that the resulting weight gain is a critical part of a healthy pregnancy.

Studies that show low gestational weight gain (in other words, not gaining enough weight when pregnant) often results in infants with low birth weights, who may experience delayed development.  Therefore the mother’s weight determines foetal weight: if she does not gain enough weight, the foetus may remain small simply to protect the mother’s bodyweight.

Here are some guidelines for weight gain during pregnancy:-

  • 30-40lb (13-18Kg) for women starting out underweight.
  • 25-35lb (11-16Kg ) for women starting out at a normal/ideal weight
  • 15-25lb (7-11Kg) for women starting out overweight, or women 5’2″ of shorter.

To achieve this weight gain, women will need up to an additional 300-500 kcals per day, and closer to 500 if exercising regularly.  This means total intake could climb to 2500 or even 3000 kcal per day during pregnancy.

According to the the UK NHS, Start 4 Life nutrition website, women in their first trimester are encouraged to continue to eat the same amount of calories as they did prior to becoming pregnant.  This is because as you adjust to being pregnant, you would become more sedentary thus saving calories.  It is in the third trimester that calorie needs increase by 300-500 kcals.

Of course if the food choices are sound during this increased intake, pregnant women will also benefit from an increase in vitamins, minerals and phytonutrients.  This is also critical to mother’s health as well as the health of developing foetus.

Without enough calories and micronutrients, the rapidly developing foetus can be subject to a host of birth defects. Inadequate nutritional status during development can also have consequences for the child’s later life, even as an adult: poor nutrition during development can lead to eventual cardiovascular disease, hypertension and Type 2 diabetes years later.

During pregnancy, women are strongly encouraged to avoid the following:

  • alcohol and caffeine (no more than 300mg/day); high intakes of alcohol and caffeine can lead to birth defects and spontaneous abortion.
  • tobacco
  • cured/deli meats, raw eggs, and raw seafood, all of which carry harmful bacteria
  • artificial sweeteners (or at least significantly limit)
  • more than 6oz of fish per week, because of potential heavy metal contamination.  In particular women should avoid shark, swordfish, king mackerel and tilefish which are known to be high in mercury.
  • more than 10% calories from highly processed foods

The following nutrients should be included and/or increased during pregnancy.

Vitamins B12

Vitamin B12 is an important nutrient in cell development.  Since B12 is abundant in animal foods, omnivores may get enough B12.  However if clients are limiting their intake of animal foods, a supplement will be essential.


Folate (vitamin B9) is essential to prevent neural tube defects. Intake is most critical within the first few weeks of pregnancy. Those of childbearing age should include ample folate and typically, a folic acid supplement is recommend by many doctors.

Vitamin D

A deficiency in vitamin D can lead to minimal calcium absorption and a low infant birth weight.  Sun exposure (20-30 minutes, 2-3 times per week) is the ideal source for vitamin D.


Calcium intake can be important for the prevention of a condition known as pre-eclampsia.  Pre-eclampsia leads to hypertension and protein in the urine pf pregnant women.  Calcium needs are increased during pregnancy.


Iron is essential for many processes, especially during pregnancy.


Zinc is important not only for athletes but pregnant women.  Its role in growth and development is critical in the developing foetus. Deficiency can lead to congenital malformations.


Iodine is critical for foetal brain and nervous system development . A deficiency, which is uncommon in the western world, is the single most important cause of preventable intellectual disability and brain damage worldwide.

Iodine deficiency is also an associated risk of miscarriage, preterm delivery and stillbirth.


We would aim to increase overall protein intake by at least 25g (about 1 palm of protein dense foods) during the second and third trimesters.  This can be obtained by increased overall energy intake via whole food or by supplementing with protein supplements.

This protein becomes part of the foetus’ structural development, as approximately 2.2lb (1kg) of protein are incorporated into the development of the foetus and the placenta.

Fatty Acids

Since most women are advised to limit intake of large fish (eg tuna) due to potential environmental pollutants, toxins and contaminants during pregnancy, pregnant women should get an ample amount of omega-3 fatty acids from other foods including flax, chia, walnuts, hemp, small fish (eg herring) green leafy vegetables and seaweed.

Supplementation with omega-3 fish oil rich in EPA and DHA has also been shown to be beneficial for both mother and child.  This will improve infant brain development during pregnancy and help to prevent preterm birth and may reduce the incidence of postpartum depression in the mother after giving birth.

It’s important though to avoid oil that comes from the liver of fish , such as cod liver oil, as it can provide potentially toxic levels of Vitamins A and D.


The Essentials of Sports & Exercise Nutrition 3rd Edition – Precision Nutrition

ROAR – How to match your food and fitness to your female physiology – Stacy T. Sims PhD

NHS Start 4 Life Website – Pregnancy nutrition.






About the Author

James Belbin is the Uk's most experienced Precision Nutrition ProCoach.  Since 2016 James has been providing clients support and guidance to optimise their nutrition.  Currently studying evidence-based nutrition, James ultimate goal is to reduce the burden of obesity on the population of the UK.



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