Most pregnant women should gain about 1 pound per week during the second trimester, which works out to roughly 12 to 14 pounds over those 14 weeks. The exact target depends on your pre-pregnancy BMI, whether you’re carrying one baby or multiples, and how much you gained in the first trimester. The guidelines most doctors still use come from the Institute of Medicine’s 2009 recommendations, which remain the current standard.
Weekly Targets by BMI Category
The second trimester is when weight gain picks up noticeably. In the first trimester, most women gain only 1 to 4 pounds total. Starting around week 14, the pace increases to a steady weekly rate that varies by your starting weight.
For a single pregnancy, here’s what the guidelines recommend per week during the second and third trimesters:
- Underweight (BMI under 18.5): about 1 to 1.3 pounds per week, with a total pregnancy gain of 28 to 40 pounds
- Normal weight (BMI 18.5 to 24.9): about 0.8 to 1 pound per week, with a total pregnancy gain of 25 to 35 pounds
- Overweight (BMI 25 to 29.9): about 0.5 to 0.7 pounds per week, with a total pregnancy gain of 15 to 25 pounds
- Obese (BMI 30 or higher): about 0.4 to 0.6 pounds per week, with a total pregnancy gain of 11 to 20 pounds
In practice, the observed range of weekly gain during the second trimester spans from about 0.7 to 1.4 pounds per week across all women. That’s a wide range, and small fluctuations from week to week are completely normal. Water retention, a larger meal the night before, or a bowel movement can shift the scale by a pound or more on any given day. The weekly rate matters more as an average trend over several weeks than as a number you hit precisely each time you step on the scale.
Twin Pregnancies Need a Faster Pace
If you’re carrying twins, the targets are significantly higher. Research on favorable twin outcomes points to a total gain of 35 to 45 pounds, which means aiming for about 1.5 pounds per week during the second and third trimesters. That’s roughly double the rate for a normal-weight woman carrying one baby. The extra gain supports two placentas, a larger uterine volume, and the growth needs of both babies.
Where the Weight Actually Goes
It can feel unsettling to watch the scale climb steadily for months, but very little of the gain is body fat. By the end of pregnancy, the roughly 30 pounds a typical woman gains breaks down like this: the baby accounts for about 7.5 pounds, the placenta adds 1.5 pounds, and amniotic fluid adds another 2. Your uterus grows to about 2 pounds heavier than its pre-pregnancy size. Breast tissue adds around 2 pounds.
The rest is your body’s support system. Blood volume increases dramatically during pregnancy, adding about 4 pounds. Other body fluids (the extra fluid in your tissues that can make your ankles swell) contribute another 4 pounds. Maternal fat stores, which your body lays down to fuel breastfeeding later, account for about 7 pounds. Much of this resolves in the weeks and months after delivery.
Calorie Needs in the Second Trimester
Gaining at the right pace doesn’t require dramatic changes to how much you eat. The second trimester calls for roughly 300 extra calories per day beyond what you normally need, bringing most normal-weight women to about 2,200 calories daily. That’s the equivalent of a banana with peanut butter and a glass of milk, not the “eating for two” overhaul many people imagine.
Those 300 calories do the most good when they come from nutrient-dense foods, since your needs for iron, folate, calcium, and protein all increase during the second trimester. The calorie target is an average. Some days you’ll eat more because you’re genuinely hungry, and other days less because you’re not. What matters is the overall pattern across weeks.
Why Gaining Too Little Is Risky
Insufficient weight gain is linked to a higher chance of having a smaller-than-expected baby. In one study of underweight women, 27% of those with insufficient gain delivered a small-for-gestational-age infant, compared to about 12% of those who gained enough. Inadequate gain also correlated with higher rates of restricted fetal growth (17% versus 4%) and premature rupture of membranes (42% versus 19%).
These risks are most pronounced for women who were underweight before pregnancy, but they apply across BMI categories. If you’re consistently gaining less than half a pound per week during the second trimester and you started at a normal weight, that’s worth raising with your provider. Morning sickness that persists into the second trimester, food aversions, or simply not feeling hungry enough are common reasons women fall short.
Why Gaining Too Much Is Also a Concern
Excessive gain is associated with delivering a larger baby, which can increase the likelihood of a cesarean delivery, and with retaining more weight after pregnancy. The link between high gain and gestational diabetes or preeclampsia is less clear than many people assume. Research results have been inconsistent, and some studies find no significant association at all, particularly in women who started pregnancy at a healthy weight. Still, gaining well above the guidelines does shift the odds toward a bigger baby and a harder time returning to your pre-pregnancy weight.
A sudden jump of several pounds in a single week, especially in the late second or early third trimester, is worth paying attention to not because of fat gain but because rapid swelling can be an early sign of preeclampsia. If you notice your face or hands becoming puffy alongside a sharp spike on the scale, contact your provider.
How to Track Your Gain Practically
Weighing yourself once a week at the same time of day, in similar clothing, gives you the most useful data. Daily weigh-ins tend to cause unnecessary anxiety because normal fluid shifts can mask or exaggerate the real trend. What you’re looking for is a roughly steady upward slope when you plot your numbers across weeks, not perfection at each individual data point.
If you gained very little in the first trimester due to nausea, you may find the second trimester gain feels rapid by comparison. That’s typical. If you gained more than expected in the first trimester, you don’t need to restrict calories to “make up for it,” but it’s reasonable to aim for the lower end of the weekly range going forward. The goal is a healthy total by the end of pregnancy, and there’s flexibility in how you get there.