How Much Weight Should You Gain in the Second Trimester?

For a healthy pre-pregnancy BMI, expect to gain about 0.5 to 1 pound per week in the second and third trimesters.

You’ve probably heard the phrase “eating for two” tossed around like a free pass. But when the second trimester starts and your bump becomes noticeable, many people suddenly wonder if they’re gaining too much or too little. It’s one of those pregnancy questions that feels simple but turns out to be surprisingly personal.

The honest answer is that healthy second-trimester weight gain depends almost entirely on where you started. Your pre-pregnancy BMI sets the target, and you don’t need to guess — the guidelines from major medical groups give clear weekly ranges that can help you stay on track.

Understanding Second Trimester Weight Gain Goals

Most pregnancy weight gain happens during the second and third trimesters, not the first. In the first three months, many people gain only about 2 to 4 pounds total, sometimes less if morning sickness is significant.

By the second trimester, your body is building the placenta, increasing blood volume, and supporting rapid fetal growth. That’s when the scale starts moving more steadily. The Institute of Medicine (IOM) guidelines, backed by ACOG and the CDC, are the gold standard for setting these targets.

Your recommended weekly gain changes based on your pre-pregnancy body mass index, so comparing yourself to a friend with a different body type isn’t helpful. Your goal is unique to you.

Why Your Pre-Pregnancy BMI Changes The Equation

Two people due the same week might have very different recommended weight gain ranges. That’s because the IOM guidelines tailor the number by where you started. Here’s what the research recommends for total pregnancy weight gain based on BMI category:

• Underweight (BMI under 18.5): Target a total gain of 28 to 40 pounds over the full pregnancy, with about 1 to 1.3 pounds per week in the second and third trimesters.
• Normal weight (BMI 18.5 to 24.9): Aim for 25 to 35 pounds total, with roughly 0.8 to 1 pound per week during the second half of pregnancy.
• Overweight (BMI 25 to 29.9): The recommended range is 15 to 25 pounds total, with a slower pace of about 0.5 to 0.7 pounds per week.
• Obese (BMI 30 or greater): Expect a total gain of 11 to 20 pounds, with just 0.4 to 0.6 pounds per week in the second and third trimesters.

These numbers are based on large population studies and are meant to balance healthy fetal growth with lower risk of complications for you. Gaining significantly more or less than your BMI-based target is worth discussing with your provider.

Weekly Gain Ranges Based On Your Starting Weight

A peer-reviewed study published by the NIH provides slightly more granular weekly ranges that line up with the IOM totals. For normal-weight women, the mean weekly gain in the second and third trimesters is 0.8 to 1 pound. For those who started overweight, the range drops to 0.5 to 0.7 pounds — roughly half a pound each week.

If you started in the obese category, the target narrows to 0.4 to 0.6 pounds per week. The Mayo Clinic’s guide on overweight weight gain guidelines notes that for people with a BMI of 25 or higher, gaining about half a pound a week is typical, and an extra 300 calories per day is often enough to meet that goal.

These weekly targets aren’t meant to be hit perfectly every seven days — some weeks you’ll gain a little more, others a little less. The overall trend is what matters.

These ranges come from the IOM guidelines and the longitudinal study data. If your weight gain seems off by more than a pound from one week to the next, it’s usually not a reason to worry — but a consistent pattern outside your range is worth mentioning at your next prenatal visit.

How To Hit Your Weekly Target

Hitting your weekly target doesn’t require complicated math. Small, consistent changes to your eating habits typically do the trick. Here are practical steps based on the CDC and Mayo Clinic recommendations:

1. Add about 340 extra calories per day during the second trimester if you were at a healthy weight before pregnancy. That’s roughly a yogurt with fruit and a handful of nuts — not a whole extra meal.
2. Aim for around 300 extra calories if you started overweight or obese. You may not need as much of a bump to stay on the slower gain track.
3. Focus on nutrient-dense choices rather than empty calories. Protein, healthy fats, and fiber keep you full and support your baby’s development without excess sugar.
4. Weigh yourself once a week at the same time of day, ideally in the morning before breakfast. Consistent tracking helps you see the trend without fixating on daily fluctuations.
5. Talk to your provider if you’re gaining less than half a pound per week or more than 2 pounds per week for several weeks in a row. A quick adjustment to your diet or activity level can bring things back in line.

Your appetite may naturally increase in the second trimester, but listening to hunger cues and eating balanced meals is usually enough to land within your target range without measuring every calorie.

What About The Last Trimester?

The third trimester continues with the same weekly gain guidelines based on your pre-pregnancy BMI, but your calorie needs increase slightly. The CDC notes that you’ll need roughly 450 extra calories per day during the third trimester to support ongoing fetal growth and your body’s preparation for birth.

Per the healthy weight gain per week guidance from ACOG, the weekly pace doesn’t change. If you were gaining 0.5 to 1 pound per week in the second trimester, you should expect a similar pace in the third — unless your provider advises otherwise due to conditions like gestational diabetes or high blood pressure.

Near the end of pregnancy, some people notice the scale slows down or plateaus. That’s often normal, but if you have concerns about sudden changes or lack of movement, your obstetrician can help sort out whether it’s related to fluid, your baby’s position, or something else.

The Bottom Line

Second-trimester weight gain doesn’t have to be a guessing game. Knowing your pre-pregnancy BMI and the corresponding weekly target gives you a clear framework. Add a few hundred extra calories from whole foods, weigh yourself weekly, and trust the gradual trend over any single number on the scale.

Your obstetrician or midwife can help you fine-tune your weekly target based on your health history and your baby’s growth pattern — especially if your BMI puts you in a higher-risk category or if you have specific nutritional needs that require tailoring the general guidelines.