Healthy Weight Gain in Pregnancy, the Role of Diet and Exercise

"Now you're eating for two" is a common adage during pregnancy. This myth has been around for many years and has created a social norm that has contributed to the growing concerns surrounding the obesity epidemic in the United States. 

But how do you achieve healthy weight gain in pregnancy, and what role do diet and exercise play? This article aims to provide some insight into healthy pregnancy weight gain and the role of diet and exercise.

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Understanding Healthy Pregnancy Weight Gain Guidelines

Any health decisions during pregnancy should start with a discussion with your prenatal care team. The American College of Obstetrics and Gynecology (ACOG) and the Institute of Medicine (IOM) recommend some general guidelines.

Weight gain during pregnancy generally depends on pre-pregnancy BMI and whether the pregnancy is singleton or multiples. For a singleton pregnancy, pre-pregnancy BMI and weight gain recommendations are as follows:

• BMI < 18.5: 28-40 lbs.
• BMI 18.5-24.9: 25-35 lbs.
• BMI 25-29.9: 15-25 lbs.
• BMI ≥ 30: 11-20 lbs.

The weight gain recommendation for twin gestation is 25-62 lbs. depending on pre-pregnancy weight. Recent studies suggest that almost 50% of women gain more weight than is recommended during pregnancy, while around 20% of women gain too little.

Risks of Inappropriate Weight Gain in Pregnancy

Both too little and too much weight gain in pregnancy can have risks for both mom and baby.

Risk of Inadequate Weight Gain

Inadequate weight gain during pregnancy heightens the risk of premature birth or a small for gestational age (SGA) baby. This risk appears dose-dependent: The further below the recommended weight gain, the higher the risk of small infant size or preterm birth.

Risk of Excessive Weight Gain

Conversely, excessive weight gain during pregnancy carries other risks, including:

• Large babies, who are at increased risk of health complications both short- and long-term
• Gestational hypertension
• Preeclampsia
• Gestational diabetes
• The need for cesarean delivery
• Increased risk of childhood obesity

Excessive weight gain in pregnancy can also increase the risk of weight retention in the mother after delivery and is a predictor of excessive weight gain and complications in future pregnancies.

Risks Factors for Inappropriate Weight Gain in Pregnancy

Many factors may contribute to too much or too little weight gain in pregnancy. According to a recent meta-analysis, being underweight before conception is linked to an increased risk of inadequate or severely inadequate weight gain in pregnancy, while being overweight or obese carries an increased risk of excessive weight gain.

Other risk factors for low weight gain in pregnancy are:

• Smoking
• HIV infection
• Diarrhea or nausea
• Malaria infection
• Lower level of education
• Lower socioeconomic status

Risk factors for excessive weight gain in pregnancy include:

• Quitting smoking
• Lower education level
• Lower socioeconomic status
• Excessive weight gain in previous pregnancy
• Unhealthy dietary patterns

Role of Diet During Pregnancy

The idea of "eating for two" is a social construct that increases the risk of obesity in pregnancy by promoting the idea that pregnancy is a time to gain weight freely. While there are two people to consider, nutritional needs only increase by 300-500 kcal/day during pregnancy.  The focus of diet during pregnancy should be on high-quality food with adequate macro and micronutrients.

Macronutrients 

Protein needs vary by trimester and increase throughout pregnancy. One study suggests that 10-35% of energy consumption during pregnancy should be protein, equating to about 71 grams daily. In the first trimester, intake should be around 1g/day of additional protein, but this need is closer to an extra 26g/day by the third trimester.

During pregnancy, carbohydrates comprise 45-65% of energy consumption, while fat makes up 20-35%.

Fat consumption should focus on healthy fats like omega-3 fatty acids to promote fetal brain and eye development. 

Micronutrients

Other nutrients that are important during pregnancy:

• Iron (30-60 mg/day) 
• Folate (at least 600 mcg/day) 
• Calcium (1.5-2 g/day)
• Vitamin D (at least 600 IU/day)

The diet during pregnancy generally focuses on whole fruits and veggies, whole grains, proteins, low-fat or fat-free dairy, and healthy oils such as omega-3 fatty acids. 

To enhance omega-3 fatty acid intake, consume seafood that is low in mercury, such as anchovy, catfish, crab, salmon, whitefish, or tilapia. Prenatal vitamins can help improve the intake of some micronutrients recommended during pregnancy.

Other Dietary Considerations

Alcohol consumption during pregnancy is not recommended according to the American College of Obstetricians and Gynecologists (ACOG) due to the risk of fetal alcohol syndrome. This condition is associated with abnormal facial features, impaired brain development, small head size, and small stature.

Role of Exercise During Pregnancy

Engaging in moderate exercise is generally considered safe during pregnancy, but women must seek guidance from their prenatal care providers before starting an exercise program.

Benefits

There are several proven benefits of exercise during pregnancy.  Some of these include: 

• Decreased back pain
• Less constipation and bloating
• Less swelling
• Improved sleep, energy, and mood
• Improved posture
• Increased muscle tone and endurance, which may help with the labor process
• Improved ability to lose weight after pregnancy
• Reduced risk of excessive weight gain
• Decreased risk of gestational diabetes, preeclampsia, and cesarean section

Risks

While exercise is generally beneficial during pregnancy, some women with higher-risk conditions may need to avoid it. Conditions such as bleeding in pregnancy, preterm labor, or high blood pressure may require caution. 

For most women, the benefits outweigh the risks, but pregnant women consult their obstetrical team before starting any exercise program. 

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Key Takeaways

• Most women gain too much or too little weight during pregnancy.
• The best way to assess healthy weight gain in pregnancy is a discussion with a prenatal care provider.
• A balanced diet with the recommended macro and micronutrients can support healthy weight gain.
• For most low-risk women, exercise is safe, healthy, and beneficial.  
• It is essential for healthcare providers to educate patients about healthy weight gain at all stages of pregnancy, from preconception to delivery.