Most women gain about 12 to 14 pounds during the second trimester, which works out to roughly a pound per week across those 13 weeks (weeks 14 through 27). The exact target depends on your pre-pregnancy weight, but that pound-per-week pace is the benchmark for women who started pregnancy at a normal BMI.
Weekly Targets by Pre-Pregnancy BMI
Weight gain recommendations for the second and third trimesters are set as weekly rates rather than trimester totals, since the pace matters more than hitting a single number at the end. Here’s what those rates look like for a singleton pregnancy:
- Underweight (BMI under 18.5): about 1 pound per week
- Normal weight (BMI 18.5 to 24.9): about 1 pound per week
- Overweight (BMI 25 to 29.9): about 0.6 pounds per week
- Obese (BMI 30 or higher): about 0.5 pounds per week
Over 13 weeks, that translates to roughly 13 pounds for underweight and normal-weight women, about 8 pounds for overweight women, and about 6.5 pounds for obese women. These are averages. Some weeks you might gain two pounds, other weeks nothing, and that’s completely normal. The trend over several weeks matters far more than any single weigh-in.
Why the Second Trimester Feels Different
During the first trimester, most women gain only 1 to 4.5 pounds total. Nausea, food aversions, and a still-tiny fetus keep the number low. The second trimester is when the pace picks up noticeably, and there’s a reason for that: your baby is growing rapidly, your blood volume is expanding by nearly 50%, and your body is building the placenta, adding amniotic fluid, and laying down fat stores that will fuel breastfeeding later.
This is also when appetite tends to return or even ramp up. Your body needs about 300 extra calories per day during the second trimester compared to your pre-pregnancy intake, bringing the typical daily total to around 2,200 calories. That’s not a dramatic increase. It’s roughly the equivalent of a yogurt parfait with fruit and granola, or a peanut butter sandwich. You don’t need to “eat for two” in any literal sense.
Where the Weight Actually Goes
It’s easy to assume that gaining a pound a week means you’re putting on body fat, but most of the weight during the second trimester is going to places other than your fat stores. By the end of pregnancy, a typical weight breakdown looks something like this: the baby accounts for about 7 to 8 pounds, the placenta adds 1.5 pounds, amniotic fluid adds about 2 pounds, your uterus grows by about 2 pounds, breast tissue adds a pound or more, and the extra blood your body produces accounts for roughly 3 to 4 pounds. Additional fluid retention and some fat storage make up the rest.
During the second trimester specifically, much of the gain comes from expanding blood volume and fluid, the growing placenta, and the baby’s transition from a few ounces to about 2 pounds by week 27. The fat storage that supports later pregnancy and breastfeeding is also accumulating, but it’s only one piece of the picture.
Twin Pregnancy Targets
If you’re carrying twins, the total recommended gain across the entire pregnancy is significantly higher: 37 to 54 pounds for normal-weight women, 31 to 50 pounds for overweight women, and 25 to 42 pounds for obese women. There aren’t separate weekly benchmarks published specifically for the second trimester with twins, but the overall gain is roughly 1.5 times higher than for a singleton, and the second trimester is when much of that accelerated growth begins. Your provider will likely monitor your weight more closely and adjust targets based on how the pregnancy is progressing.
What Happens if You Gain Too Much
Gaining significantly more than the recommended range raises the risk of gestational diabetes, high blood pressure, and having a larger-than-average baby, which can complicate delivery. Excess gain also tends to be harder to lose postpartum and is associated with a higher likelihood of needing a cesarean birth. A few weeks of faster gain isn’t cause for alarm on its own, but a consistent pattern of exceeding the targets is worth discussing with your provider. Small changes, like swapping calorie-dense snacks for more protein and fiber, can make a meaningful difference without requiring anything drastic.
What Happens if You Gain Too Little
Gaining below the recommended range carries its own risks. Insufficient weight gain is linked to premature birth and low birth weight (under 5.5 pounds at birth), both of which can lead to health complications for the baby. It also means your body may not be storing enough fat to support the energy demands of late pregnancy and early breastfeeding. If nausea from the first trimester is lingering, or you’re struggling to eat enough, nutrient-dense foods and smaller, more frequent meals can help you catch up gradually. Persistent difficulty gaining weight deserves a conversation with your care team, since sometimes an underlying issue like thyroid dysfunction or severe food aversion is at play.
Practical Ways to Track Your Gain
Weighing yourself once a week at the same time of day, ideally in the morning before eating, gives you the most consistent picture. Daily weigh-ins tend to create unnecessary stress because water retention alone can swing your weight by a pound or two from one day to the next. Write the number down or use an app so you can see the trend line over weeks rather than fixating on any single reading.
If you notice you’re consistently above or below the weekly targets for your BMI category, that’s useful information to bring to a prenatal visit. Your provider can look at the overall curve and factor in things like your height, muscle mass, and how the baby is measuring. The guidelines are population-level averages, not rigid rules, and individual variation is expected. What matters most is a steady, gradual upward trend rather than sharp spikes or long plateaus.