Most women gain between 11 and 40 pounds during pregnancy, with the exact target depending on pre-pregnancy BMI. A woman at a normal weight before conceiving should aim for 25 to 35 pounds total. These ranges come from guidelines originally set by the Institute of Medicine and still endorsed by both the CDC and the American College of Obstetricians and Gynecologists as of 2025.
Recommended Ranges by BMI
Your pre-pregnancy body mass index is the single biggest factor in how much weight you’re expected to gain. The current guidelines break it down into four categories:
- Underweight (BMI below 18.5): 28 to 40 pounds
- Normal weight (BMI 18.5 to 24.9): 25 to 35 pounds
- Overweight (BMI 25.0 to 29.9): 15 to 25 pounds
- Obese (BMI 30.0 to 39.9): 11 to 20 pounds
These ranges exist because women who start pregnancy at a higher weight already carry additional energy reserves, so they need less added weight to support a healthy pregnancy. Women who are underweight need more to ensure adequate nutrition reaches the baby.
Where the Weight Actually Goes
A common worry is that pregnancy weight gain is “all fat,” but most of it is biological infrastructure your body builds to grow and sustain a baby. Here’s the approximate breakdown for a woman who gains around 30 pounds:
- Baby: 7 to 8 pounds
- Placenta: 1.5 pounds
- Amniotic fluid: 2 pounds
- Uterus growth: 2 pounds
- Breast tissue: 1 to 3 pounds
- Increased blood volume: 3 to 4 pounds
- Maternal fat stores: 6 to 8 pounds
Your blood volume increases by nearly 50% during pregnancy, which accounts for several pounds on its own. The fat stores aren’t wasted weight either. Your body lays them down deliberately to fuel breastfeeding after delivery. So out of 30 total pounds, only about 6 to 8 are actual body fat, and even that fat has a purpose.
How the Gain Should Be Paced
Weight gain isn’t evenly distributed across all nine months. During the first trimester, most women gain only 1 to 4 pounds total. Some gain nothing, especially if morning sickness is severe, and that’s generally not a concern.
The real acceleration happens in the second and third trimesters, when the baby is growing fastest. For women at a normal pre-pregnancy weight, gaining roughly a pound per week during these months is typical. Women who were overweight before pregnancy generally aim for about half a pound per week in those later months.
Calorie needs follow a similar pattern. The first trimester requires little to no extra food. During the second trimester, about 2,200 calories per day supports healthy growth (compared to roughly 1,800 in the first trimester). By the third trimester, that rises to about 2,400 calories per day. The often-quoted advice to “eat for two” overstates it considerably. The real increase works out to about 300 extra calories a day on average, which is roughly a banana with peanut butter and a glass of milk.
Weight Gain With Twins
If you’re carrying twins, the targets are significantly higher. For women at a normal pre-pregnancy weight, the recommended gain is 37 to 54 pounds. Overweight women carrying twins should aim for 31 to 50 pounds, and obese women for 25 to 42 pounds. No official guidelines exist for triplets or higher-order multiples because the data is too limited to set reliable targets.
Risks of Gaining Too Much
Exceeding the recommended range raises the odds of several complications. Gestational diabetes becomes more likely, which means your body can’t manage blood sugar efficiently during pregnancy. This can cause the baby to grow unusually large (a condition called macrosomia), which in turn increases the chance of a difficult delivery or cesarean section. Excessive gain also raises the risk of preeclampsia, a dangerous spike in blood pressure that can threaten both mother and baby.
There’s a longer-term effect too. Women who gain well above the guidelines tend to retain more weight after delivery, which can make subsequent pregnancies higher risk and contribute to lasting changes in metabolic health.
Risks of Gaining Too Little
Gaining less than recommended carries its own set of problems, particularly for the baby. Insufficient weight gain is a recognized risk factor for intrauterine growth restriction, where the baby’s estimated weight falls below the 10th percentile for its gestational age. Babies affected by growth restriction face higher rates of premature birth and cesarean delivery. They can also have difficulty regulating body temperature and blood sugar after birth.
This is especially relevant for women who are underweight before pregnancy or who experience prolonged nausea that limits food intake well into the second trimester. Gaining at least the lower end of your BMI range gives the baby the best chance of reaching a healthy birth weight.
What Matters More Than the Scale
The guidelines are ranges, not rigid rules. A woman who gains 36 pounds with a normal pre-pregnancy BMI (one pound over the upper limit) isn’t in a fundamentally different situation than one who gains 34. What tends to matter more is the pattern of gain: steady and gradual is better than a sudden spike in one trimester followed by a plateau.
Nutrient quality also outweighs calorie counting for most women. Protein supports the baby’s tissue development, iron and folate prevent anemia and neural tube defects, and calcium keeps your own bones intact while the baby’s skeleton forms. A diet built around whole foods, with reasonable portions, typically lands within the right calorie range without much tracking.
If your weight gain is tracking significantly above or below the guidelines by mid-pregnancy, your provider will likely adjust your nutrition plan or investigate underlying causes. A single weigh-in that looks high or low rarely matters. The overall trend across weeks is what tells the real story.