During the second trimester (weeks 14 through 27), most women should gain about 1 pound per week, putting the total second trimester gain in the range of 12 to 14 pounds. That rate applies to women who started pregnancy at a normal weight. Your specific target depends on your pre-pregnancy BMI, whether you’re carrying multiples, and how much you gained in the first trimester.
Weekly Targets by BMI Category
The Institute of Medicine guidelines, endorsed by ACOG, set both total pregnancy gain and weekly rate targets. For the second and third trimesters, steady weekly gain matters more than any single weigh-in. Here’s how the numbers break down:
- Underweight (BMI below 18.5): Total gain of 28 to 40 pounds, with a weekly rate of roughly 1 to 1.3 pounds starting in the second trimester.
- Normal weight (BMI 18.5 to 24.9): Total gain of 25 to 35 pounds, with about 1 pound per week in the second and third trimesters.
- Overweight (BMI 25 to 29.9): Total gain of 15 to 25 pounds, with about half a pound per week in the second and third trimesters.
- Obese (BMI 30 or higher): Total gain of 11 to 20 pounds, with about half a pound per week.
Most women gain only 1 to 5 pounds during the entire first trimester, so the bulk of pregnancy weight gain happens from week 14 onward. If you gained very little (or even lost weight from nausea) in your first trimester, your provider may suggest a slightly faster pace now. The reverse is also true: gaining more than expected early on doesn’t mean you need to “make up for it” by restricting later.
Twin Pregnancy Targets
If you’re carrying twins, the numbers increase significantly. A woman who started at a normal weight should gain 37 to 54 pounds total over the course of a twin pregnancy. That typically means a faster weekly rate in the second trimester, often 1.5 pounds per week or more. Your provider will likely track your gain more closely with twins, since adequate early weight gain is especially important for fetal growth when two babies are sharing resources.
Where the Weight Actually Goes
It can help to understand that second trimester weight gain isn’t just body fat. By the end of pregnancy, a typical 30-plus-pound gain breaks down roughly like this: the baby accounts for about 7.5 pounds, the placenta adds 1.5 pounds, and the uterus itself grows by about 2 pounds. Amniotic fluid adds another 2 pounds, and breast tissue grows by about 2 pounds as it prepares for milk production.
The rest is your body’s support system. Blood volume nearly doubles during pregnancy, adding around 4 pounds. Extra body fluids (the swelling in your feet and ankles) account for another 4 pounds. The remaining weight is a combination of fat stores your body builds to fuel breastfeeding and the energy demands of late pregnancy. Much of this growth accelerates during the second trimester, which is why the scale starts moving more noticeably now.
Calorie Needs in the Second Trimester
Supporting this growth doesn’t require as many extra calories as you might expect. During the first trimester, you need about 1,800 calories per day. In the second trimester, that rises to about 2,200 calories, an increase of roughly 300 calories over your pre-pregnancy baseline. That’s the equivalent of a yogurt with fruit and a handful of nuts, or a small sandwich. The third trimester bumps the target to around 2,400 calories per day.
Quality matters more than quantity here. Your body needs more protein, iron, calcium, and folate during this period. Eating nutrient-dense foods helps you hit your weight targets without overshooting, and it supports the rapid fetal development happening between weeks 14 and 27, when your baby’s organs are maturing and bones are hardening.
Risks of Gaining Too Little or Too Much
Falling well below the recommended range increases the risk of premature birth and having a baby with a low birth weight (under 5.5 pounds). Babies born too small can face breathing difficulties, trouble maintaining body temperature, and longer-term developmental challenges. If your weight plateaus for two or more weeks during the second trimester, it’s worth mentioning to your provider.
Gaining significantly more than recommended carries its own set of problems. Excess weight gain raises the likelihood of gestational diabetes, preeclampsia (a dangerous condition involving high blood pressure and potential organ damage), and the need for a C-section delivery. It can also make postpartum weight loss harder and increase the baby’s risk of being unusually large at birth, which complicates delivery for both parent and child.
A few weeks of faster or slower gain are completely normal. What matters is the overall trend across the trimester, not any single week. Water retention, constipation, and meal timing can all cause the number on the scale to jump around day to day.
Tracking Your Weight Gain
Most prenatal visits during the second trimester are scheduled every four weeks, and your provider will weigh you at each one. That monthly check is enough for most women. If you want to monitor at home, weighing yourself once a week at the same time of day (morning, before eating) gives you a more reliable picture than daily weigh-ins, which tend to fluctuate by a pound or two from fluid shifts alone.
If you notice your gain is consistently above or below the targets for your BMI category, your provider can help adjust your nutrition plan. Small changes, like adding a protein-rich snack or swapping calorie-dense drinks for water, are usually enough to bring the trajectory back on track without dramatic dietary overhauls.