Weight Gain During Pregnancy: How Much Is Too Much or Not Enough?

How much weight to gain during pregnancy is a common concern. Gaining too much weight can put you at risk of multiple problems that could affect you and your baby’s health. On the other hand, not gaining enough weight can also be problematic. The potential consequences of too little or too much weight gain can occur during pregnancy, delivery, or the postpartum period. 

How much weight should you gain each trimester?

The recommended amount of weight to gain during pregnancy is based on your body size before you became pregnant. In particular, experts recommend weight gain based on your BMI (a number calculated from your height and weight). 

The standard weight-gain recommendations based on prepregnancy BMI are:  

• If your BMI is less than 18.5: at least 28 pounds and up to 40 pounds

• If your BMI is 18.5 to 25: 25 pounds to 35 pounds 

• If your BMI is 25 to 30: 15 pounds to 25 pounds

• If your BMI is greater than 30: 11 pounds to 20 pounds 

People usually gain only a few pounds in the first trimester. Most of your weight gain should occur in the second and third trimesters. This typically means you’ll gain 10 pounds to 15 pounds in both the second and third trimesters, depending on your weight at the beginning of your pregnancy. Weight gain tends to taper off as you get closer to your due date. 

What is the average weight gain in pregnant women?

One study of pregnant women found the average weight gain among all participants was about 30 pounds. However, other studies have shown that almost half of pregnant people gain more than the recommended amount. In fact, according to one study, almost 50% of pregnant people gain more weight than desired, while around 20% of people report not gaining enough weight. 

Like weight-gain recommendations, actual weight gain during pregnancy depends on your prepregnancy weight. Underweight people are more likely to gain less than the recommended amount when pregnant. At the same time, those who start pregnancy with larger bodies tend to gain more than the guidelines suggest. 

Where does the extra weight go?

You might wonder where the extra weight during pregnancy goes, since the baby is less than 10 pounds. About one-third of it is accounted for by your growing baby, the placenta, and the amniotic fluid. The rest of the weight goes to increasing maternal body parts. For example, as your baby grows, the uterus must also grow. Also, the amount of blood flowing through your arteries and veins must expand, and your breasts must enlarge to prepare for breastfeeding. 

What factors contribute to weight gain during pregnancy?

Many factors likely contribute to weight gain during pregnancy. However, our prepregnancy body weight appears to be the primary influence. 

Here’s a breakdown of the potential contributing factors for pregnancy weight gain:

• Pregestational body weight: Your weight before pregnancy is the largest predictor of weight gain during pregnancy. 

• Height: Most studies account for the influence of height by recommending weight gain based on BMI. Taller women tend to have bigger babies. But height does not appear to be a significant factor in weight gain.

• Ethnicity and/or race: Studies suggest as much as 50% of underweight Black and Hispanic women do not gain enough during pregnancy.

• Age: The effect of age on weight gain during pregnancy is unclear. Some studies show an association between inadequate weight gain, leading to small babies, for young mothers. Other studies have shown the opposite or no increased risk for this group. And older moms have additional risk factors for excessive and insufficient weight gain, so the effect of age alone is difficult to determine. 

• Parity (number of births): Weight gain tends to be higher with your first pregnancy. But it also depends on your prepregnancy weight. Those who start pregnancy with a low BMI are more likely to have inadequate weight gain.

• Smoking: Smoking while pregnant has many risks, including preterm birth, low birth weight, and stillbirth. Smokers appear to gain the same amount of weight as non-smokers during pregnancy. However, quitting smoking is a risk factor for increased weight gain.

• Socioeconomic status (based on income, occupation, and education): The relationship between weight gain and socioeconomic status is complicated, and the data is mixed. But lower socioeconomic status is associated with obesity, which contributes to both too much and not enough weight gain during pregnancy. 

• Exercise: Exercising while pregnant is safe and recommended. Mothers who remain active during pregnancy are less likely to gain excessive weight. However, high levels of prepregnancy activity may increase the risk for excessive weight gain in people with obesity, but the data is conflicting. This may be due to a reduction in activity as pregnancy progresses. 

What is excessive weight gain during pregnancy?

Excessive weight gain during pregnancy is any weight gain above the recommended amount. This has been linked to health problems such as:

• Gestational diabetes

• Pregnancy-induced hypertension (high blood pressure) or preeclampsia

• Increased risk of cesarean delivery

• Maternal obesity

After gaining excessive weight during pregnancy, it’s hard to lose it. And weight gain increases the risk of developing Type 2 diabetes, chronic hypertension, and metabolic syndrome. It also increases the risk of complications in a future pregnancy.

Excessive weight gain during pregnancy can also cause problems for your baby, such as:

• Macrosomia (larger than average baby)

• Hypoglycemia (low blood sugar)

• Childhood obesity 

Is it safe to lose weight when pregnant?

Losing weight is not recommended during pregnancy. Gaining too little weight during pregnancy comes with the risk of having a small baby who has trouble feeding and fighting infections after birth. In addition, insufficient pregnancy weight gain is linked to an increased risk of infant death for up to 1 year. 

Certain circumstances can make weight gain difficult during pregnancy. Severe morning sickness, also known as hyperemesis gravidarum, is the most common. Milder morning sickness usually resolves by the second trimester, when fetal growth and weight gain increase. 

The good news is that eating a healthy diet, staying active, and working with your healthcare provider can help you stay within the recommended range of pregnancy weight gain. If you have struggled with not enough or too much weight in previous pregnancies, be sure to reach out to your provider for guidance.

Why trust our experts?

Written by:

Katherine Killoran, MD

Katherine Killoran, MD, is a board-certified gynecologist with more than 20 years of clinical experience.

Edited by:

Mandy Armitage, MD

Mandy Armitage, MD, has combined her interests in clinical medicine with her passion for education and content development for many years. She served as medical director for the health technology companies HealthLoop (now Get Well) and Doximity.

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