What to Eat in the Third Trimester

A healthy third trimester diet could prevent your baby from developing childhood obesity.

Pregnant Woman Eating Pizza
Photo: Dasha Petrenko/Shutterstock

Pregnancy is well-known for its food cravings and the old adage of "eating for two." What is less discussed is the link between your prenatal diet and the health of your baby. But even if your pregnancy eating has been less than stellar during your first and second trimesters, it's not too late to turn things around in the home stretch. In fact, the third trimester is the perfect time to get on track with healthy eating.

Research shows that the foods you eat now (and during lactation, if you breastfeed) can impact your baby's health long after they're born, according to research published in Cell. Specifically, eating a high-fat diet at the end of pregnancy may increase your baby's risk of developing childhood obesity and other chronic health conditions. Learn more about why your prenatal nutrition matters and the dietary changes to consider making in your third trimester.

How Maternal Diet Impacts Your Baby

While the study was on animals, scientists believe its results are relevant to humans as well. Researchers found that the offspring of mice that were fed a high-fat diet during lactation—the equivalent of the third trimester in humans—had an increased risk of being overweight throughout their lives.

Why? The critters born to parents consuming a fatty diet experienced changes in the hypothalamus, a part of the brain that regulates metabolism. This occurred whether the parenting mice were plump or lean, meaning maternal diet has an impact on offspring regardless of the weight of the parent. So, it is the nutrients eaten during pregnancy (and during lactation) that really matter.

"The third trimester is a very important time in the development of your baby's metabolism," says Tamas Horvath, Ph.D., professor at the Yale University School of Medicine, and co-author of the study. "It's when the brain develops connections associated with metabolic processes."

A 2021 study in Nutrients on pregnant people in Brazil also found that you eat during pregnancy, particularly in the third trimester, can have a big impact on the developing baby both before birth and in childhood. Unhealthy diets, such as those low in fruits, fiber, and vegetables and high in saturated fats and processed foods, resulted in increased risks of complications for infants.

These health issues included low birth weight, childhood obesity, diabetes, and other chronic conditions. Researchers believe these babies have nutrient deficits due to the subpar maternal diet. In fact, according to the authors of another study, babies exposed to nutritional deficiencies in utero are "programmed" to eat more in childhood because they develop fewer neurons in the region of the brain that controls food intake.

What to Eat in the Third Trimester

According to a 2022 study in the American Journal of Obstetrics and Gynecology, maternal nutrition during pregnancy and lactation has lifelong consequences for babies. Specifically, the researchers recommend "basing diet on a variety of nutrient-dense, whole foods, including fruits, vegetables, legumes, whole grains, healthy fats with omega-3 fatty acids that include nuts and seeds, and fish, in place of poorer quality highly processed foods."

Additionally, the study authors suggest pregnant people focus on eating better rather than eating more during pregnancy, as "most women in the United States do not meet the recommendations for healthful nutrition and weight before and during pregnancy."

The American College of Obstetricians and Gynecologists (ACOG) echoes these concerns and suggestions, noting that: "Eating well is one of the best things you can do during pregnancy."

But don't worry! It's never too late to start eating well—and prenatal vitamins can help fill in any gaps. Plus, a healthy diet doesn't mean eliminating every food you love (or crave). Instead, simply aim to find a healthier balance by adding in fruits, veggies, and other whole foods while reducing high-fat processed items. Moreover, there's no need to trim the fat from your diet altogether.

In fact, it's important to consume enough fats as they are key to a well-balanced diet. "Healthy fats are important in the third trimester to support your pregnancy and prepare for lactation," says Rebecca Scritchfield, R.D. and founder of Capitol Nutrition Group, which specializes in prenatal care.

The key is focusing on fats that come from whole foods (like nuts, seeds, avocados, olive oil, eggs, salmon, lean meats, yogurt, and cheese), rather than the processed saturated and trans fats you'll find in packaged foods. "Whole foods supply vitamins and minerals, along with healthy fat," adds Scritchfield.

Should I Change My Pregnancy Eating Habits?

Shifting your diet away from processed foods and saturated fats and towards healthier foods is always a good idea. However, it's important to note that you never want to diet to lose weight or otherwise severely constrict your calories during pregnancy. The key is to replace less nutrient-dense foods with those that offer more benefits for you and your baby. Under-eating during pregnancy is just as dangerous as overeating.

Consult with your prenatal medical provider with any questions you have about your diet. Any big dietary changes should always be guided by your doctor. Additionally, a nutritionist with expertise in prenatal nutrition can also be a great resource. They can help you make an effective healthy eating plan.

The Bottom Line

Optimal nutrition during pregnancy is all about eating a balanced diet high in whole foods and low in saturated fats and highly processed foods. However, note that every body is different (and beautiful)—and you may have slightly different nutritional needs than someone else. So, check in with your doctor to make sure you are following the ideal prenatal diet for you and your baby.

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