Pregnancy Nutrition Calculator
Get your personalised calorie, protein, iron, folate, and calcium targets for each trimester of pregnancy. Includes gestational weight gain guidance based on pre-pregnancy BMI.
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Medical note: This calculator provides general guidance only. Always discuss your nutrition needs with your midwife, obstetrician, or registered dietitian during pregnancy.
Pregnancy Nutrition: The Evidence-Based Overview
Pregnancy nutrition is one of the most consequential nutritional periods in a woman's life. Adequate intake of key nutrients, particularly in the first trimester, when most organ systems are forming, has lifelong health implications for the child.
Despite this, most pregnancy nutrition advice is vague ("eat well, avoid these foods") without providing the specific targets that would allow women to actually monitor adequacy. This calculator provides evidence-based targets by trimester.
The Trimester Nutrition Differences
Each trimester has distinct nutritional priorities:
- First trimester: Folate/folic acid is critical, the neural tube closes at approximately week 4, often before pregnancy is confirmed. This is why folate supplementation is recommended for all women of reproductive age. Calorie needs are essentially unchanged. Nausea management is often the primary concern, small, frequent protein-rich meals work best.
- Second trimester: Most rapid period of foetal growth. Iron needs increase significantly as maternal blood volume expands by ~45% and the placenta develops. Energy needs increase by approximately 340 kcal/day. This is often the most comfortable trimester for eating.
- Third trimester: The baby gains approximately 50% of its birth weight in this period. Energy needs peak (~450 kcal/day above pre-pregnancy). Calcium and vitamin D are critical for foetal bone mineralisation. Smaller, more frequent meals are typically more comfortable as the growing uterus compresses the stomach.
Foods to Avoid During Pregnancy
Certain foods carry significant risk during pregnancy and should be avoided:
- Raw/undercooked meat, fish, and eggs, risk of Listeria, Salmonella, Toxoplasma
- High-mercury fish, shark, swordfish, marlin, tilefish, king mackerel (limit tuna to 2 portions/week)
- Unpasteurised dairy and soft mould-ripened cheeses, Listeria risk
- Deli meats and pâté, Listeria risk unless heated until steaming
- Raw sprouts, bacterial contamination risk
- Alcohol, no safe level established in pregnancy
- High-dose vitamin A supplements, teratogenic at high doses (liver is also very high in vitamin A)
Frequently Asked Questions
How many extra calories do you need during pregnancy?
The additional calorie needs vary by trimester. First trimester: approximately 85 extra kcal/day (the foetus is tiny, "eating for two" in the first trimester is a myth). Second trimester: approximately 340 extra kcal/day. Third trimester: approximately 450 extra kcal/day. These figures are from the Academy of Nutrition and Dietetics and align with NHS and WHO guidelines. The exact amount varies by pre-pregnancy weight, height, and activity level.
How much protein do you need when pregnant?
Protein needs increase during pregnancy to support foetal growth, placental development, and expansion of maternal blood volume and tissues. The minimum is 71g/day (WHO), but most practitioners recommend 1.1–1.2g/kg of pre-pregnancy bodyweight. For a 65kg woman, this means approximately 72–78g/day, notably higher than typical non-pregnant recommendations, and important throughout all three trimesters.
What nutrients are most critical during pregnancy?
The most critical nutrients with highest risk of deficiency: Folate/folic acid (400–600mcg/day, prevents neural tube defects, critical in first trimester and before conception); Iron (27mg/day, blood volume expands 45% in pregnancy); Vitamin D (400 IU/day minimum, NHS recommendation); Iodine (200mcg/day, thyroid function and neurological development); DHA omega-3 (200mg/day, brain development); Calcium (1,000mg/day, bone mineralisation). A prenatal supplement covers most of these.
Is it safe to exercise during pregnancy?
In the absence of complications, moderate exercise is safe and beneficial throughout pregnancy. Recommended: 150 minutes/week of moderate-intensity aerobic activity (brisk walking, swimming, prenatal yoga, low-impact cycling). Exercise reduces the risk of gestational diabetes, pre-eclampsia, excessive weight gain, and postnatal depression. Avoid contact sports, activities with fall risk (after first trimester), and lying flat on your back (after 16 weeks). Always consult your midwife or OB before starting or continuing any exercise programme.
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