Healthy weight gain during pregnancy can help prevent pregnancy complications such as gestational diabetes, preeclampsia, and cesarean delivery.
The amount of weight a woman can safely gain during pregnancy depends on her pre-pregnancy Body Mass Index (BMI), a calculation based on height and weight that can provide a better estimate of total body fat than weight alone.
The Centers for Disease Control (CDC) weight gain recommendations for women pregnant with one baby are as follows in the table below.
| Pre-pregnancy BMI | Safe weight gain |
|---|---|
| Underweight: BMI less than 18.5 | 28 to 40 pounds |
| Normal weight: BMI 18.5 to 24.9 | 25 to 35 pounds |
| Overweight: BMI 25 to 29.9 | 15 to 25 pounds |
| Obese: BMI 30 or greater | 11 to 20 pounds |
The Centers for Disease Control (CDC) weight gain recommendations for women pregnant with twins are as follows in the table below.
| Pre-pregnancy BMI | Safe weight gain |
|---|---|
| Underweight: BMI less than 18.5 | 50 to 62 pounds |
| Normal weight: BMI 18.5 to 24.9 | 37 to 54 pounds |
| Overweight: BMI 25 to 29.9 | 31 to 50 pound |
| Obese: BMI 30 or greater | 25 to 42 pounds |
About one-third of women gain the recommended amount of weight during pregnancy and most women gain weight outside the recommendations (21% gain too little, 48% gain too much).
It is important to gain the recommended amount of weight during pregnancy because:
- Gaining too little during pregnancy is associated with delivering a baby who is too small, and the baby may:
- Have difficulty starting breastfeeding
- Be at increased risk for illness
- Experience developmental delays
- Gaining too much weight during pregnancy is associated with delivering a baby who is too large
What Accounts for Weight Gain During Pregnancy?
Weight gain during pregnancy can be attributed to the following:
- Baby: 7 or 8 pounds
- Larger breasts: 1 to 3 pounds
- Larger uterus: 2 pounds
- Placenta: 1-1/2 pounds
- Amniotic fluid: 2 pounds
- Increased blood volume: 3 to 4 pounds
- Increased fluid volume: 2 to 3 pounds
- Fat stores: 6 to 8 pounds
How Can A Woman Meet Pregnancy Weight Gain Recommendations?
A woman should determine her weight gain goals with her doctors at the start of pregnancy, and revisit them regularly throughout the pregnancy.
- Track pregnancy weight gain regularly throughout pregnancy and note how your progress compares to the recommended ranges of healthy weight gain
- Eat a balanced diet
- Consume plenty of whole grains, vegetables, fruits, low-fat dairy, and lean protein
- Limit added sugars and fats found in foods like soft drinks, desserts, fried foods, whole milk dairy products, and fatty meats
- Identify calorie needs for each trimester
- During the first trimester (first three months) women do not usually require any extra calories
- During the second trimester (second three months) women usually need about 340 additional calories per day
- During the third (last three months) trimester women usually need about 450 additional calories per day
- Aim for a minimum of 150 minutes (2-1/2 hours) of moderate-intensity aerobic activity (such as brisk walking) per week
From 
Pregnancy and Parenting Resources
https://americanpregnancy.org/healthy-pregnancy/pregnancy-health-wellness/pregnancy-weight-gain-968/