Signs of Hormonal Imbalance

Doctor P explains pregnancy weight gain targets by BMI, why first-trimester weight loss is normal, and when not gaining enough becomes a real concern for your baby.

Is It Healthy To Lose Weight During Pregnancy?

June 3, 2026

The positive test arrived while you were six weeks into something that was finally working. You had a plan, a rhythm, a reason for every meal, and then the rules changed and nobody told you what came next. Do you stop? Do you adjust? Do you trust the influencer who was eight months pregnant and still doing everything, or the voice telling you that this is not the time?

The question underneath all of it is the same one: is my baby okay?

That is what this article is here to answer. Intentional weight loss during pregnancy is not recommended. But that single sentence does not give you what you actually need, which is an understanding of what is normal, what is concerning, and what the evidence says about your baby’s development when the scale is not moving in the direction your provider wants.

Quick answer: Intentional weight loss is not recommended during pregnancy. Weight loss in the first trimester is common and often expected, driven by nausea, food aversions, and morning sickness. What matters most is not the number on the scale but consistent, nutrient-dense eating that supports your baby’s development. If weight loss continues beyond the first trimester, that belongs in a conversation with your provider.

Doctor P, board-certified OB/GYN, explains the eating-for-two myth, BMI-based weight gain targets, and what the evidence says about weight and fetal development.

The Eating for Two Myth — and What Your Body Actually Needs

Here is something I want to address before anything else. You are not eating for two. This is one of the most persistent myths I encounter as an OB/GYN, and it matters because it has real consequences. Women who follow the eating-for-two idea often gain significantly more than their clinical target during pregnancy, and that excess weight is frequently the hardest weight to lose after delivery.

Your body needs only 200 additional calories per day in the first trimester. That is roughly an apple and a handful of crackers. The increment grows modestly: 300 to 350 additional calories daily in the second trimester, and approximately 400 in the third. These are not dramatic adjustments.

What pregnancy actually requires is not more food. It is better food. The focus belongs on nutrient density, meaning protein, carbohydrates, and healthy fats present at every meal, rather than on volume. Building balanced, nutrient-dense meals consistently is more meaningful than tracking the scale. If you are doing that, you are doing the right thing.

Why Weight Changes During Pregnancy and When It Becomes Concerning

Weight loss in pregnancy is not automatically a problem, but the trimester matters. The same number means something very different in week eight than it does in week twenty-four. Here is how to think about each phase.

First Trimester Weight Loss Is Expected

In the first trimester, losing weight is extremely common. Nausea, food aversions, morning sickness, and fatigue all make consistent eating difficult. Your appetite changes week to week, and some days getting through a plain meal is an achievement. Losing weight under these conditions is not a failure and does not signal that your baby is in danger.

Most people move through this phase and find eating normal again as they enter the second trimester. The first-trimester dip does not predict how nutrition will go for the rest of the pregnancy.

Hyperemesis Gravidarum — When It Goes Beyond Morning Sickness

A small percentage of pregnancies involve hyperemesis gravidarum (HG), a severe form of nausea and vomiting that extends well beyond typical morning sickness. HG affects roughly 0.3% to 3% of pregnancies and is the second leading cause of hospitalization during pregnancy in the United States, behind preterm labor.

According to NIH clinical data, HG typically resolves between 16 and 20 weeks of gestation, but in approximately 20% of cases it persists throughout the entire pregnancy. In these situations, weight loss is a medical reality that often requires hospitalization, IV fluids, and nutritional support to stabilize.

If you are vomiting multiple times a day and cannot keep fluids down, call your OB/GYN. This is a clinical situation, not a level of discomfort to manage alone.

Second and Third Trimester Weight Loss Is a Different Conversation

Once the first trimester ends, weight loss or failure to gain becomes a concern for a different reason. Your body is in active development, and insufficient nutrition raises questions beyond calories, including electrolyte balance, organ function, and fetal growth.

Weight loss in later pregnancy is sometimes a signal of an underlying condition. Thyroid dysfunction and blood sugar irregularities are occasionally first diagnosed during prenatal care. Providers are watching more closely, and conditions that were easy to overlook become visible under that level of monitoring. If you are losing weight or not gaining in the second or third trimester, your provider needs to know. Call ahead of your next appointment if it feels significant, rather than waiting to bring it up.

Pregnancy Weight Gain Goals by BMI

How much weight you should gain during pregnancy depends on where you started. The clinical targets established by the Institute of Medicine and endorsed by ACOG are based on pre-pregnancy BMI (body mass index).

Pre-Pregnancy BMI	BMI Range	Recommended Total Gain
Underweight	Below 18.5	28 to 40 lbs
Normal weight	18.5 to 24.9	25 to 35 lbs
Overweight	25.0 to 29.9	15 to 25 lbs
Obese	30.0 and above	11 to 20 lbs

If you started underweight, the target range is the highest and the minimum matters most. You have fewer fat reserves for your body to draw on, which is why gaining more is essential. If you started at a higher BMI, your body has stored energy reserves, and the lower gain target reflects that.

There are no official guidelines for intentional weight loss during pregnancy, regardless of starting weight. The clinical goal is not a number on the scale. It is consistent nourishment and appropriate fetal growth, which your provider monitors at each prenatal visit. Two women at the same starting weight can have very different clinical pictures. What they are eating and how their babies are growing matters more than the scale alone.

If you are very physically active and burning more calories than a sedentary person, your weight may not move as expected. That is not automatically a concern. The real measure is your baby’s growth, which your provider assesses directly.

What's at Stake When Your Baby Doesn't Get Enough

The risks of insufficient gestational nutrition are real and worth understanding clearly. A large-scale analysis of 9.1 million U.S. births examined what happens when women gain below the recommended range. Preterm birth, low birth weight, and small for gestational age were all significantly more common compared to women who stayed within the guideline range.

The specific risks Doctor P covers in the video: small for gestational age, preterm labor and delivery, increased likelihood of NICU admission, and impaired fetal brain development. The brain is particularly sensitive to what happens nutritionally during pregnancy. Fetal brain development draws heavily on available energy and micronutrients throughout gestation, and insufficient supply during critical development windows is associated with lasting effects.

The point here is not to create fear around the scale. It is to make clear that nutrition during pregnancy is not about appearance or postpartum weight. It is about giving your baby’s systems what they need to form correctly. Staying focused on consistent, nutrient-dense prenatal eating and keeping that communication open with your provider is the work that matters.

Doctor P created the Ultimate Hormone Assessment for women who want clarity on what is happening in their body. If hormonal concerns existed before this pregnancy or you are navigating postpartum changes after it, that is a practical starting point.

What Pregnancy Can Reveal About Your Hormones

Pregnancy surfaces conditions that were already present but not yet identified. Thyroid dysfunction, insulin resistance, and other hormonal patterns sometimes go unrecognized for years before prenatal care brings them into view. Providers are watching more closely, and what was easy to overlook becomes visible under that level of monitoring. If a new diagnosis arrives during pregnancy, it is often not that something went wrong. It is that the right person finally looked.

The postpartum period brings its own distinct hormonal shift. Estrogen and progesterone drop sharply after delivery. For many women, this is the first time they recognize how significantly hormones have been affecting how they feel day to day. Doctor P’s guide on how hormones affect weight explains the mechanisms clearly, and the hormone reset deep dive addresses what weight management looks like on the other side.

Frequently Asked Questions

Is it okay to lose weight during the first trimester of pregnancy?

Yes. First-trimester weight loss is common and expected. Nausea, food aversions, and morning sickness make consistent eating difficult for most pregnant women in early pregnancy. Losing weight during this phase does not mean something is wrong with your pregnancy. Most women return to more normal eating patterns as they move into the second trimester. If weight loss continues past the first trimester or you cannot keep food or fluids down, contact your OB/GYN.

What are the recommended pregnancy weight gain goals based on BMI?

Targets are based on pre-pregnancy BMI. Underweight women (BMI below 18.5) should gain 28 to 40 lbs total. Normal weight women (BMI 18.5 to 24.9) should gain 25 to 35 lbs. Overweight women (BMI 25 to 29.9) should gain 15 to 25 lbs. Women with obesity (BMI 30 and above) should gain 11 to 20 lbs. These are clinical targets, not rigid rules. Your provider individualizes guidance based on how your pregnancy is progressing and how your baby is growing.

Can not gaining enough weight during pregnancy harm my baby?

Yes. Research shows that gaining below the recommended range significantly increases risk of preterm birth, low birth weight, and small for gestational age. Fetal brain development is particularly sensitive to maternal nutrition throughout pregnancy. This is not about one difficult week of eating. It is about sustained inadequate intake over time. If you are not gaining as expected, the conversation to have with your provider is about nutrition quality and what might be driving the pattern.

What causes weight loss during pregnancy?

First-trimester weight loss is most commonly caused by nausea, vomiting, and food aversions. For a smaller number of women, hyperemesis gravidarum causes severe and prolonged vomiting that can persist well past the first trimester and requires medical treatment. In the second and third trimesters, unexpected weight loss may point to an underlying condition, a nutritional deficiency, or insufficient caloric intake. Any weight loss beyond the first trimester needs evaluation by your OB/GYN.

Should I continue a weight loss plan after finding out I am pregnant?

No. Intentional weight loss is not recommended during pregnancy. The goal shifts from weight loss to nutrient adequacy and appropriate gestational gain. This applies regardless of starting weight. Women with a higher pre-pregnancy BMI have lower gain targets, and existing fat stores provide some nutritional buffer, but this does not make caloric restriction safe. Focus on consistent, balanced meals and talk to your provider about any concerns around your weight or nutrition during pregnancy.