Which Trimester Do You Gain the Most Weight During Pregnancy?

How much weight should you gain during pregnancy?

You don't need to gain much weight during the first trimester, however, during the second and third trimesters your weight gain should be pretty steady.
You don't need to gain much weight during the first trimester, however, during the second and third trimesters your weight gain should be pretty steady.

Gaining a healthy amount of weight during your pregnancy is important for you and your baby. If you don't gain enough weight, your baby may be too small. Babies who are born too small may have trouble breastfeeding, be more prone to illness, and be developmentally delayed. If you gain too much weight, you're more likely to have a premature baby or a baby who is very large. You are also more likely to have a C-section and have trouble losing weight after your baby is born.

How much weight you should gain during pregnancy depends on what your body mass index (BMI) was before you got pregnant. If you were underweight before pregnancy, you'll need to gain more weight than someone who was overweight. Your doctor can tell you the best amount of weight to gain, but the general guidelines for women pregnant with one baby are:

  • If you were underweight (BMI less than 18.5), you should gain between 28 and 40 pounds.
  • If you were normal weight (BMI between 18.5 and 24.9), you should gain between 25 and 35 pounds.
  • If you were overweight (BMI between 25 and 29.9), you should gain between 15 and 25 pounds.
  • If you were obese, (BMI of 30 or more), you should gain between 11 and 20 pounds.

How much you should gain by trimester

However, when you gain weight is important, too. You don't need to gain much weight during the first trimester. You may be relieved to hear that if you've been having a hard time keeping food down because of morning sickness. You should only gain 1 to 4 pounds during the first trimester. You don't need to add any extra calories during this trimester, just eat a healthy diet.

During the second and third trimesters, your weight gain should be pretty steady at one-half to 1 pound weekly, depending on how much you should gain. Since the second and third trimesters are both around 13 weeks, you'd expect to gain the same amount in each one. However, for many women, weight gain slows or stops in the last month. Because of this, most women gain the most weight during their second trimester of pregnancy.

Where does the weight go?

Since your baby will probably weigh around 7 or 8 pounds, you may be wondering why you need to gain more than that. Every woman is different, but here's a general breakdown of how the weight is distributed:

  • Baby, 7.5 pounds
  • Placenta, 1.5 pounds
  • Amniotic fluid that surrounds your baby, 2 pounds
  • Increased blood, 4 pounds
  • Other body fluids, 3 pounds
  • Breasts, 2 pounds
  • Fat, protein, and other nutrients, 6 to 8 pounds
  • Uterus, 2 pounds

The healthy way to gain weight during pregnancy

On average, you'll only need about 340 extra calories per day during the second trimester and 450 in the third. That's a far cry from "eating for two." Here are some tips to help you gain a healthy amount of weight during pregnancy.

Eat a healthy diet

Your diet doesn't need to change that much during pregnancy. You'll still need to eat a healthy diet with lots of fruits, vegetables, whole grains, low-fat dairy, and lean protein. There are some foods you should avoid when you're pregnant because of the risk of foodborne illnesses. These include:

  • Raw or undercooked seafood, including sushi
  • Refrigerated, smoked seafood that hasn't been cooked
  • Unpasteurized juice or cider
  • Raw milk products, including milk and soft cheese
  • Raw or undercooked eggs
  • Premade meat or seafood salad
  • Raw sprouts
  • Undercooked meat or poultry
  • Hot dogs or luncheon meat that hasn't been reheated to 165 degrees F.
  • Refrigerated meat spreads from the deli or refrigerated section
  • Raw dough

Limit added sugars and solid fat

Though you need extra calories, they should come from healthy foods, not added sugar and saturated fat. Avoid foods such as:

  • Fatty meats
  • Desserts
  • Fried foods
  • Whole milk
  • Soda

Track your weight gain

Work with your doctor or midwife to keep track of how much weight you're gaining throughout your pregnancy. Compare it to the healthy guidelines to make sure you're staying on track.

Exercise regularly

If you've been exercising regularly, keep it up during your pregnancy. If you're not used to exercising, work your way up to at least 150 minutes of exercise weekly. You can break it up into 30-minute sessions 5 days per week. Talk to your doctor to be sure exercising is safe for you, but most women will benefit from staying physically active while pregnant. Exercise can help you feel better and avoid gaining too much weight.


The first sign of pregnancy is most often: See Answer
Centers for Disease Control and Prevention: "Weight Gain During Pregnancy."

March of Dimes: "Weight Gain During Pregnancy."

Institute of Medicine (US) and National Research Council (US) Committee to Reexamine IOM Pregnancy Weight Guidelines: "Weight Gain During Pregnancy: Reexamining the Guidelines."