Most pregnant women should gain between 25 and 35 pounds over the full nine months, but the right number for you depends on your pre-pregnancy weight. The Institute of Medicine sets specific ranges based on BMI, and these guidelines are used by major medical organizations including the CDC and ACOG.
Recommended Gain by Pre-Pregnancy BMI
Your starting weight is the single biggest factor in how much you should gain. The guidelines break down like this for a single pregnancy:
- 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 or higher): 11 to 20 pounds
If you’re carrying twins, those numbers go up significantly. Women at a normal pre-pregnancy BMI should gain 37 to 54 pounds with twins. Overweight women carrying twins should aim for 31 to 50 pounds, and obese women for 25 to 42 pounds.
Where the Weight Actually Goes
It’s easy to assume the extra pounds are all baby, but the baby typically accounts for only 7 to 8 pounds at birth. The rest supports the pregnancy in specific, necessary ways:
- Placenta: about 1.5 pounds
- Amniotic fluid: about 2 pounds
- Breast tissue: 1 to 3 pounds
- Fat stores: 6 to 8 pounds
Your body also increases its blood volume by nearly 50% during pregnancy and retains extra fluid, both of which add several more pounds. The fat stores aren’t excess weight in the usual sense. Your body builds them deliberately to fuel breastfeeding and recovery after delivery.
How Gain Should Pace Across Trimesters
Weight gain isn’t evenly distributed over 40 weeks. During the first trimester, most women gain only 1 to 4 pounds total. Some gain nothing at all, especially if morning sickness is severe. That’s normal and not a concern.
The real growth happens in the second and third trimesters, when you can expect to gain roughly 1 pound per week if you started at a normal weight. Women who were overweight before pregnancy typically gain a bit less per week, closer to half a pound. This is when the baby is growing fastest, the placenta is fully developed, and your blood volume peaks.
Caloric needs shift to match this pattern. You don’t need any extra calories in the first trimester. In the second trimester, about 400 additional calories per day supports healthy growth, rising to roughly 600 extra in the third trimester. For context, that second-trimester increase is about 2,200 calories total per day, and third trimester about 2,400, for most normal-weight women.
Risks of Gaining Too Much
Exceeding the recommended range is linked to several complications. Excessive gain increases the chance of having a larger-than-average baby, which raises the likelihood of a cesarean delivery and can cause complications during vaginal birth. It also increases risk for gestational diabetes and preeclampsia, a dangerous blood pressure condition.
There’s a lasting effect too. Women who gain well above the guidelines have a harder time losing the weight afterward. Postpartum weight retention is one of the strongest predictors of long-term weight gain, and it compounds with each subsequent pregnancy.
Risks of Gaining Too Little
Gaining below the recommended range carries its own set of problems. Low weight gain in the second or third trimester is strongly associated with having a baby that’s too small at birth, a condition called intrauterine growth restriction. In two large studies, women who gained less than about two-thirds of a pound per week during the second trimester had roughly double the risk of delivering a growth-restricted baby compared to women who gained at a normal rate. The pattern held in the third trimester as well.
Interestingly, low gain in the first trimester alone didn’t carry the same risk. It’s the sustained growth period of mid- and late pregnancy where inadequate nutrition has the most impact on fetal size.
What Happens Right After Delivery
Most women lose 10 to 13 pounds immediately after giving birth. That accounts for the baby, the placenta, and amniotic fluid. Over the next few weeks, you’ll shed additional water weight as your blood volume returns to normal and your body releases the extra fluid it retained during pregnancy.
The remaining pounds, mostly the fat stores your body built intentionally, come off more gradually. For women who gained within the recommended range, most of the pregnancy weight is typically gone within 6 to 12 months, though the timeline varies widely. Breastfeeding burns roughly 500 extra calories a day, which helps but isn’t a guarantee of faster loss.
Tracking Without Obsessing
Your provider will weigh you at every prenatal visit and flag any trends that fall outside the expected range. If you’re gaining too quickly, small adjustments to portion sizes and activity level are usually enough to get back on track. If you’re not gaining enough, your provider may recommend calorie-dense, nutrient-rich foods or investigate whether nausea, food aversions, or another condition is interfering with intake.
Week-to-week fluctuations are completely normal. Water retention, meal timing, and even the time of day can swing the scale by a few pounds. The overall trend across weeks matters far more than any single weigh-in. If your trajectory is roughly within the guidelines for your BMI category, the exact number on the scale at any given appointment is less important than the pattern over time.