The average recommended weight gain during pregnancy is 25 to 35 pounds for someone starting at a healthy weight. But that number shifts significantly depending on your pre-pregnancy body size, and most people don’t actually land within the recommended range. Only about 1 in 3 women gain the guideline amount, while roughly half gain more than recommended and 1 in 5 gain less.
Recommended Gain by Body Size
Your pre-pregnancy BMI is the single biggest factor in how much weight you’re expected to gain. The guidelines, originally set by the Institute of Medicine and used by the CDC and most OB-GYNs, break down like this:
- Underweight (BMI below 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 higher): 11 to 20 pounds
These ranges exist because someone carrying more body fat before pregnancy already has energy reserves the body can draw on. Someone starting underweight needs to build those reserves from scratch, which is why their target is higher.
How the Weight Breaks Down
It’s easy to assume pregnancy weight gain is mostly fat, but the baby itself only accounts for about 6 to 8 pounds at birth. The rest is spread across your body in ways that support the pregnancy: the placenta (about 1.5 pounds), amniotic fluid (roughly 2 pounds), increased blood volume (3 to 4 pounds), breast tissue growth (1 to 3 pounds), and an enlarged uterus (about 2 pounds). Maternal fat stores, which your body lays down to fuel breastfeeding, typically make up 5 to 9 pounds. Fluid retention adds a few more.
This means the majority of what you gain isn’t permanent. Most of it leaves your body within the first few weeks after delivery through birth itself, fluid loss, and the return of your blood volume to normal levels.
Weight Gain by Trimester
Weight gain isn’t evenly distributed across pregnancy. In the first trimester (weeks 1 through 13), most people gain very little. If you start at a healthy weight, expect only about 1 to 4 pounds total during those early months. Some people gain nothing or even lose a small amount due to nausea.
The real accumulation happens in the second and third trimesters, from week 14 through delivery. For someone at a healthy or underweight starting point, the target is roughly 1 pound per week. If you start out overweight or obese, a slower pace of about half a pound per week is typical for those later months.
Your calorie needs follow the same pattern. The first trimester doesn’t require extra calories at all. In the second trimester, you need about 340 additional calories a day, and in the third trimester, about 450 extra. That’s roughly a substantial snack, not a second dinner.
Why Gaining Too Much Matters
Exceeding the guidelines isn’t just about postpartum weight retention. A large meta-analysis covering 1.6 million women found that gaining above recommendations raised the risk of cesarean delivery by 37%, increased the chance of a larger-than-expected baby by 77%, and made pregnancy-related high blood pressure conditions 37% more likely. Babies born to mothers who gained excessively were also 26% more likely to need intensive care after birth.
Interestingly, the relationship between weight gain and gestational diabetes is less straightforward than you might expect. Studies have produced mixed results depending on the population and starting BMI, so excess weight gain isn’t as clearly tied to gestational diabetes as it is to the other complications listed above.
The extra pounds also tend to stick around. Women who gain well above the guidelines are more likely to retain significant weight a year or more after delivery, which can affect health in future pregnancies and long-term cardiovascular risk.
Risks of Gaining Too Little
Gaining below the recommended range carries its own set of problems, particularly for the baby. Insufficient weight gain increases the likelihood of delivering a low-birthweight infant (under 5 pounds, 8 ounces) and raises the risk of preterm birth. Low-birthweight babies face higher rates of breathing problems, infection, and developmental challenges in the newborn period.
The same meta-analysis found that women who gained below recommendations were more likely to have a baby measuring small for gestational age. On the other hand, they had a lower rate of cesarean delivery and were less likely to have an abnormally large baby, so the trade-offs run in both directions.
Twin and Multiple Pregnancies
If you’re carrying twins, the targets are higher across all BMI categories. Someone at a normal pre-pregnancy weight carrying twins is generally advised to gain 37 to 54 pounds. Overweight individuals carrying twins typically aim for 31 to 50 pounds, and those starting at an obese BMI are guided toward 25 to 42 pounds. The pace of gain is faster too, since two babies, two placentas, and a greater blood volume all demand more from the body earlier in pregnancy.
What Steady Gain Looks Like in Practice
Week-to-week fluctuations are completely normal. Water retention, meal timing, and even constipation can swing the scale by a few pounds in either direction on any given day. What matters is the overall trend over weeks and months, not individual weigh-ins.
A sudden jump of several pounds in a week, especially in the third trimester, is worth mentioning to your provider. Rapid weight gain can sometimes signal fluid retention related to preeclampsia rather than normal pregnancy changes. Similarly, losing weight or gaining nothing over several consecutive weeks in the second or third trimester may prompt your provider to check on fetal growth.
Tracking your own gain doesn’t need to be obsessive. A weekly weigh-in at roughly the same time of day, wearing similar clothing, gives you enough data to spot the overall pattern without turning the scale into a source of anxiety.