Your body burns roughly 300 extra calories per day during pregnancy on average, but that number varies dramatically by trimester. In the first trimester, the increase is barely noticeable. By the third trimester, your resting metabolism alone can burn nearly 400 extra calories daily compared to your pre-pregnancy baseline. Here’s how that breaks down and what drives it.
Calorie Burn by Trimester
During the first trimester, your body’s resting metabolic rate rises by only about 60 calories per day. Once you account for the small amount of weight gained early on, the true metabolic increase is closer to 20 extra calories. That’s essentially nothing, which is why most guidelines say you don’t need any additional food during the first 13 weeks.
The second and third trimesters are where things ramp up significantly. Your resting metabolism climbs by about 17 additional calories per day each week throughout this period, reaching a combined increase of roughly 390 calories per day by late pregnancy. The American College of Obstetricians and Gynecologists recommends eating an extra 340 calories per day in the second trimester and about 450 in the third to keep pace with this rising demand.
Why Your Body Burns More
Less than half of the increased calorie burn comes from simply carrying more weight. The rest, over 50%, is driven by the biological machinery of pregnancy itself. Your heart pumps a significantly higher volume of blood, your lungs work harder, and the fetus becomes increasingly metabolically active as it grows. These processes all consume energy even while you’re sitting still.
Hormonal shifts also play a role early on. Rising levels of progesterone and other pregnancy hormones nudge your metabolism upward in the first trimester before the fetus is large enough to account for much energy use on its own. By the third trimester, the fetus’s own tissues, the placenta, and the energy cost of fetal movement all contribute meaningfully to total calorie burn.
How Activity Levels Shift
While your resting metabolism rises, most pregnant women naturally compensate by moving less intensely. A study of healthy, moderately active women found that pregnant participants spent about 90 more minutes per day sitting, lying down, or sleeping compared to non-pregnant controls. They also spent over an hour less standing and about 20 fewer minutes walking, and they walked at a slower pace.
These shifts in activity reduced daily energy expenditure from movement by roughly 190 calories, offsetting a good portion of the metabolic increase. This appears to be a natural compensation rather than laziness. Your body redirects energy toward growing the baby, and you instinctively dial back physical effort. The net effect is that total daily calorie burn increases, but not as dramatically as the resting metabolism numbers alone suggest.
Twin and Multiple Pregnancies
Carrying twins pushes energy demands higher. Estimates suggest a twin pregnancy requires about 150 additional calories per day beyond what a singleton pregnancy needs, accounting for two developing fetuses, heavier maternal tissues, and greater metabolic strain. Some guidelines recommend that women carrying twins consume 700 extra calories daily in the second and third trimesters compared to their first-trimester intake.
The range of advice varies. Some providers recommend 300 to 500 extra calories, while others go as high as 1,000 additional calories per day after the 20th week (roughly 500 per baby compared to a non-pregnant baseline). Weight gain targets are also higher: 37 to 54 pounds for women of normal pre-pregnancy weight carrying twins, versus the 25 to 35 pounds typically recommended for a single baby.
How Pre-Pregnancy Weight Matters
Your starting weight affects both how many calories you burn and how many extra you should eat. Women who begin pregnancy at a higher weight already have a higher resting metabolism simply because larger bodies require more energy to maintain. The metabolic increase from pregnancy itself is layered on top of that existing baseline.
Weight gain targets reflect these differences. Women with a normal pre-pregnancy BMI are guided to gain 25 to 35 pounds total. Overweight women are advised to gain 15 to 25 pounds, and women with obesity are recommended to gain 11 to 20 pounds. These targets aren’t about restricting food arbitrarily. They reflect the fact that women starting at higher weights already have larger energy reserves available to support fetal growth.
Individual variation also exists along racial and ethnic lines. Research has found that Black women tend to have resting metabolic rates about 80 calories per day (roughly 5%) lower than white women, a difference that persists during pregnancy and mirrors patterns seen in non-pregnant populations.
After Delivery: Breastfeeding Burns More
Calorie burn doesn’t drop back to pre-pregnancy levels immediately, especially if you breastfeed. Producing breast milk requires an estimated 500 to 700 calories per day, which actually exceeds the metabolic cost of late pregnancy. This is one reason many breastfeeding women experience increased hunger and gradual postpartum weight loss even without deliberate dieting.
For women who don’t breastfeed, metabolic rate typically returns toward pre-pregnancy levels over the weeks following delivery as blood volume normalizes, the uterus shrinks, and hormonal changes settle. The timeline varies, but most of the metabolic shift reverses within a few months.