The short answer: For a woman who starts pregnancy at a healthy weight, the federal estimate is about 0 extra calories a day in the first trimester, 340 in the second, and 452 in the third. ACOG gives the same pattern and rounds the last figure to about 450. These are averages for one baby. Pre-pregnancy weight, twins, and how fast you gain all change the real number.

What are the official numbers for each trimester?

The Dietary Guidelines for Americans, 2020-2025 list the extra daily calories in Table 5-2. The numbers compare each stage with your needs before pregnancy:

  • First trimester: +0 calories a day.
  • Second trimester: +340 calories a day.
  • Third trimester: +452 calories a day.

The table applies only to women with a healthy pre-pregnancy weight. The guidelines say women with overweight or obesity should ask their health care provider about calorie intake instead.

The American College of Obstetricians and Gynecologists (ACOG) says the same thing in plain terms. Usually no extra calories are needed in the first trimester. You need an extra 340 a day in the second trimester and about 450 a day in the third.

The NIDDK pregnancy tips page repeats these figures and adds one detail. You may not need extra calories during the final weeks of pregnancy.

For scale, 340 calories is roughly a snack, not a second dinner. The guidelines say the extra should come from nutrient-dense foods. They suggest moving up to a higher calorie level of the same healthy eating pattern in the second and third trimesters.

Why are no extra calories needed in the first trimester?

The baby and the supporting tissues are still very small. NIDDK notes that the baby is about the size of a walnut in the first 3 months. It calls "eating for two" a myth.

Expected weight gain early on is small too. The Dietary Guidelines base their weekly gain targets on a first-trimester gain of 1.1 to 4.4 pounds. ACOG says you may gain 1 to 5 pounds, or none at all, in the first 12 weeks.

The body does use some extra energy early on, but the amount is small. A review by Butte and King in Public Health Nutrition estimated the energy cost of pregnancy at 375 kJ a day in the first trimester. That is about 90 calories a day, and the federal table rounds the first-trimester increase to zero.

Where do the numbers come from?

The 340 and 452 figures are Estimated Energy Requirements (EER) set by the Institute of Medicine in its 2005 Dietary Reference Intakes report. The Dietary Guidelines cite that report as the source of Table 5-2.

The method adds two costs. One is the rise in energy the body burns each day, measured as basal metabolic rate or total energy expenditure. The other is the energy stored as new protein and fat during pregnancy.

Butte and King used this approach with doubly labeled water and body composition data. For women who gained 12.0 kg (about 26 pounds), they put the total cost of pregnancy at 321 to 325 MJ. That is roughly 77,000 calories over the full pregnancy.

They spread it as 375, 1,200, and 1,950 kJ a day across the three trimesters. In calories, that is about 90, 287, and 466 a day. The second and third trimester figures sit close to the federal 340 and 452, which helps explain why the official numbers look the way they do.

The Dietary Guidelines base their sample calorie levels on a reference woman who is 5 feet 4 inches tall and weighs 126 pounds. Your own baseline may be higher or lower. If you want to estimate it, our guide on how to calculate TDEE explains the inputs. The trimester figures are added to that baseline, not to a fixed 2,000.

Does pre-pregnancy weight change the target?

Yes. The calorie table is for healthy pre-pregnancy weight only. The weight gain targets that guide the calorie number depend on body mass index (BMI) before pregnancy.

The 2009 National Academies (then IOM) guidelines, reprinted in the Dietary Guidelines, set these total gains for one baby:

  • Underweight (BMI under 18.5): 28 to 40 pounds, about 1 pound a week in the second and third trimesters.
  • Healthy weight (18.5 to 24.9): 25 to 35 pounds, about 1 pound a week (range 0.8 to 1).
  • Overweight (25 to 29.9): 15 to 25 pounds, about 0.6 pounds a week.
  • Obesity (30 or higher): 11 to 20 pounds, about 0.5 pounds a week.

A lower gain target usually means a smaller calorie increase. NIDDK says a provider may advise more calories if you are not gaining enough, and fewer if you are gaining too fast. It also says not to try to lose weight while pregnant. That makes the usual deficit math in our guide to calories to lose a pound a week the wrong tool during pregnancy.

Research in women with obesity points the same way. A 2019 study in the Journal of Clinical Investigation measured energy use with doubly labeled water in 54 pregnant women with obesity. The few who gained within the guideline ate about 125 calories a day less than they burned in the second and third trimesters. Women who gained too much ate about 186 calories a day more than they burned. The authors estimated that these women needed no increase over early-pregnancy intake for recommended gain.

The stakes run past delivery. The Dietary Guidelines say about half of women keep 10 pounds or more at 12 months postpartum. Nearly 1 in 4 keep 20 pounds or more.

What about twins or triplets?

No federal source gives a per-trimester calorie figure for twins. The Dietary Guidelines table covers one baby. NIDDK simply says needs differ if you are carrying more than one.

What does exist is a weight gain target. The 2009 National Academies report offered provisional guidelines for twins at term:

  • Healthy weight: 37 to 54 pounds.
  • Overweight: 31 to 50 pounds.
  • Obesity: 25 to 42 pounds.

The committee called these provisional because it could not run the same analysis it did for single births. It found too little data to set any range for underweight women with twins.

Advice in practice is uneven. In a 2020 survey of 276 U.S. women who had twins, about 30% said their provider's weight gain advice fell below the guidelines. Women who got low advice, or none, were more likely to gain less than recommended. If you are expecting twins, ask your provider which target applies to you.

What happens to calorie needs after birth?

If you breastfeed, needs stay above your pre-pregnancy level. The Dietary Guidelines list +330 calories a day for the first 6 months and +400 for the second 6 months.

The first figure is built from a 500-calorie cost of making milk, minus 170 calories for expected weight loss after birth. The second assumes your weight is stable by then. Our post on how many calories breastfeeding burns covers this in more detail.

Calories are only part of prenatal nutrition. ACOG says you need 600 micrograms of folic acid a day in pregnancy and advises a daily prenatal vitamin with 400 micrograms. For how prenatal supplements compare, see supplements.md.

The bottom line

The standard figures are 0, 340, and 452 extra calories a day across the three trimesters, for one baby and a healthy starting weight. They are population averages built from energy studies, not a personal prescription. Weight gain against your BMI-based target is the better day-to-day guide, and your prenatal provider is the one to set it.

Last updated: October 2026. This article is for informational purposes only and does not constitute medical advice. Talk with your obstetrician, midwife, or a registered dietitian about calorie and weight gain targets for your pregnancy.