Yes, you burn more calories when pregnant. Your body’s resting metabolic rate, the energy you burn just by existing, rises steadily across all three trimesters. By the end of pregnancy, you’re burning roughly 250 to 390 extra calories per day before you even move off the couch. But the full picture is more nuanced than a single number, because how those extra calories get used, and how your activity patterns shift, changes the real-world math considerably.
How Many Extra Calories You Burn by Trimester
The increase isn’t dramatic at first. During the first trimester, your resting metabolic rate rises by only about 30 to 60 calories per day. That’s roughly the energy in half an apple. Your body is building the placenta and expanding blood volume, but the fetus is tiny and the metabolic demands are still modest.
Things ramp up in the second and third trimesters. Resting metabolism climbs by an average of 17 calories per day per week during this stretch, adding up to around 390 extra calories per day by late pregnancy. About half of that increase is explained by the simple fact that you weigh more and it takes more energy to run a larger body. The other half comes from the biological work of growing a baby: maintaining the placenta, circulating a much larger blood volume, and supporting fetal metabolism.
The total energy cost of a full pregnancy is estimated at roughly 55,000 to 85,000 calories. The lower end comes from real-world measurements across diverse populations, while the higher figure reflects theoretical calculations that assume more fat storage.
What’s Driving the Extra Burn
Your heart starts working harder almost immediately. Cardiac output increases by 20 to 50 percent, beginning as early as five weeks of gestation and peaking around mid-pregnancy. Your heart rate rises 15 to 30 percent, and each beat pushes out 15 to 25 percent more blood. All of that pumping costs energy.
Your kidneys filter significantly more blood to handle waste from both you and the fetus. Your lungs work harder too, since oxygen demand rises throughout pregnancy. Even your digestive system requires more energy to process the nutrients being shuttled to the placenta. These organ-level changes are running constantly, which is why the calorie increase shows up in resting metabolism rather than requiring you to do anything extra.
One thing that doesn’t change much is how many calories you burn digesting food. Researchers in the Netherlands tracked this across pregnancy and found the thermic effect of meals stayed essentially constant from pre-pregnancy through week 35. So the extra burn is coming from your organs and tissues, not from processing more food.
Your Body Compensates With Less Movement
Here’s the counterintuitive part: while your metabolism is burning more at rest, you’re likely burning fewer calories through physical activity. A Swedish study comparing pregnant and non-pregnant women found that pregnant women spent about 90 extra minutes per day sitting, lying down, or sleeping. They walked 21 fewer minutes per day and moved at a slower pace (about 10 percent slower). The net result was roughly 190 fewer calories burned through activity each day.
This wasn’t laziness. The researchers described it as a natural compensation. Your body is already spending more energy on basic functions, so it nudges you toward less demanding activities. The shift almost exactly offset the metabolic increase, meaning total daily energy expenditure didn’t rise as dramatically as the resting metabolic rate alone would suggest.
How Many Extra Calories You Actually Need
The American College of Obstetricians and Gynecologists and the CDC both align on the same guidance: no extra calories are needed in the first trimester, about 340 extra per day in the second trimester, and about 450 extra per day in the third. These numbers account for both the increased metabolism and the energy being deposited in fetal tissue, the placenta, and maternal fat stores.
Those figures assume a single pregnancy. If you’re carrying twins, the estimates jump significantly. Some experts recommend an additional 150 calories per day on top of singleton recommendations, while others suggest up to 1,000 extra calories daily after the 20th week. The range depends partly on pre-pregnancy weight. Recommendations for twin pregnancies run from about 3,000 calories per day for those starting at a higher weight to 4,000 for those who are underweight.
Where the Extra Energy Goes
Not all those extra calories fuel your metabolism. A significant portion gets stored as new tissue. Classic estimates break the energy cost of pregnancy into three buckets: the increase in basal metabolism (the largest share), the growth of the baby and placenta (protein and tissue that requires energy to build), and maternal fat storage of roughly 1.3 to 3.8 kilograms. The fat stores serve as an energy reserve for breastfeeding after delivery.
The balance between these components varies widely between individuals and populations. In studies across Scottish, Dutch, Thai, and Philippine women, the total energy cost of pregnancy was similar (around 55,000 calories), but fat deposition ranged from about 3 to 5 pounds. Women who stored less fat presumably directed more energy toward metabolism and fetal growth.
How Pregnancy Compares to Breastfeeding
If pregnancy increases your calorie burn, breastfeeding pushes it even further. Producing breast milk costs an estimated 480 calories per day. In studies, breastfeeding mothers consumed about 300 more calories per day and spent about 200 fewer calories on physical activity compared to after weaning, together covering the energy cost of milk production. Exclusive breastfeeding burned a cumulative 5,520 extra calories over a two-month period compared to supplementing with formula.
Breastfeeding also shifts how your body processes fuel. Lactating women showed higher total energy expenditure, lower insulin levels, and greater carbohydrate utilization than they did after weaning. So while the third trimester adds roughly 250 to 450 calories of daily burn, exclusive breastfeeding can exceed that, making it the most metabolically demanding phase of the entire reproductive cycle.
Why Individual Variation Matters
The numbers above are averages, and individual differences can be substantial. Your pre-pregnancy weight, activity level, how much weight you gain, and your body’s metabolic efficiency all influence how many extra calories you actually burn. Someone who gains 35 pounds will have a larger increase in resting metabolism than someone who gains 20 pounds, simply because there’s more tissue to maintain. Starting BMI also plays a role in how much additional fat your body stores and how much energy gets directed toward fetal growth versus reserves.
The bottom line is straightforward: pregnancy does increase your calorie burn, primarily through a steady rise in resting metabolism driven by your heart, kidneys, and the growing fetus. But the increase is modest in the first trimester, meaningful in the second, and most pronounced in the third. Your body naturally adjusts by dialing back physical activity, so the practical increase in daily energy needs is smaller than the metabolic numbers alone would imply.