Most people should gain about 1 pound per week during the second trimester, which works out to roughly 12 to 14 pounds across those 14 weeks. That rate applies if you started pregnancy at a healthy weight or were underweight. If you started at a higher weight, the target drops to about half a pound per week. These numbers come from guidelines set by the Institute of Medicine, which remain the standard used by obstetricians today.
Weekly Targets by Starting Weight
Your pre-pregnancy BMI is the single biggest factor in how much you should gain. The second trimester (weeks 14 through 27) is when steady, consistent gain matters most, because the first trimester typically accounts for only a few pounds total.
- Underweight (BMI under 18.5): About 1 pound per week, with a full-pregnancy target of 28 to 40 pounds.
- Normal weight (BMI 18.5 to 24.9): About 1 pound per week, with a full-pregnancy target of 25 to 35 pounds.
- Overweight (BMI 25 to 29.9): About half a pound per week, with a full-pregnancy target of 15 to 25 pounds.
- Obese (BMI 30 or higher): About half a pound per week, with a full-pregnancy target of 11 to 20 pounds.
These weekly rates apply to both the second and third trimesters. If you gained very little (or even lost weight) during the first trimester due to nausea, don’t try to “make up” all the lost ground at once. A gradual return to the recommended weekly rate is what matters.
Where the Weight Actually Goes
It helps to know that the number on the scale isn’t just body fat. By the second trimester, your blood volume is expanding significantly to supply the placenta and growing baby. Amniotic fluid is increasing, the uterus is getting heavier, and breast tissue is growing. Your body also stores some fat to fuel milk production later. The baby itself weighs only about 1 to 2 pounds by the end of the second trimester, so the majority of what you gain during these weeks is supporting tissue and fluid your body needs right now.
Calorie Needs in the Second Trimester
Supporting healthy weight gain doesn’t require dramatic changes to your diet. Most normal-weight pregnant people need about 2,200 calories per day during the second trimester, which is roughly 300 extra calories beyond what you’d eat when not pregnant. That’s the equivalent of an extra snack: a cup of yogurt with fruit, a handful of nuts with cheese, or a small sandwich.
The quality of those extra calories matters more than the quantity. Protein, iron, calcium, and folate do the heaviest lifting during this stage of fetal development. If your gain is tracking on pace, you’re likely eating the right amount. If it’s consistently above or below the weekly targets, adjusting portion sizes by small amounts is usually enough to course-correct.
What Happens if You Gain Too Much or Too Little
Gaining well above the guidelines raises the risk of several complications. Gestational diabetes becomes more likely, which can cause the baby to grow larger than average (a condition called macrosomia) and make delivery more difficult. Excess gain also increases the chance of preeclampsia, a dangerous blood pressure condition that can damage your kidneys and other organs. After delivery, the extra weight is harder to lose and can contribute to long-term health issues for both parent and child.
Gaining too little carries its own risks. Inadequate nutrition in the second trimester is linked to preterm birth and low birth weight, both of which can lead to complications for the baby in the weeks after delivery. If you’re struggling to eat enough due to persistent nausea, food aversions, or other factors, that’s worth bringing up at a prenatal visit so your provider can help you find solutions early.
Weight Gain for Twin Pregnancies
If you’re carrying twins, the targets are substantially higher. For a normal-weight starting BMI, the recommended total gain is 37 to 54 pounds across the entire pregnancy. Overweight individuals carrying twins should aim for 31 to 50 pounds total, and those with a BMI of 30 or higher should target 25 to 42 pounds. These ranges translate to a noticeably faster weekly rate than singleton pregnancies, especially in the second and third trimesters when both babies are growing rapidly. For triplets or higher-order multiples, there isn’t enough data to set firm guidelines, so your care team will monitor you individually.
How to Track Your Progress
Your provider will weigh you at every prenatal appointment, which during the second trimester typically means once a month. That’s frequent enough to spot trends without obsessing over daily fluctuations. If you weigh yourself at home, keep in mind that hydration, meals, and time of day can swing the scale by a couple of pounds in either direction. The weekly average over several weeks is what matters, not any single reading.
A sudden jump of several pounds in a week, especially if paired with swelling in your hands or face, can be a sign of fluid retention related to preeclampsia rather than normal weight gain. On the other end, a plateau lasting two or three weeks in a row may signal that you’re not getting enough nutrition. Either pattern is worth mentioning to your provider at your next visit rather than waiting.