Nutrition During Pregnancy and Lactation

The National Academies of Sciences, Engineering, and Medicine last reviewed the state of the science on nutrition during pregnancy and lactation with the consensus study reports reports Nutrition During Pregnancy (1990) and Nutrition During Lactation (1991). Since then, the body of evidence on the relationships between nutrition during pregnancy and lactation, as well as maternal and infant health and chronic disease, has continued to grow and evolve. At the same time, the demographics, health, and dietary intake of the population have changed, giving rise to new considerations.

To explore new evidence, in January 2020, the Food and Nutrition Board of the National Academies convened a workshop in Washington, DC, to explore where new evidence has emerged relevant to nutrition during pregnancy and lactation.

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Macronutrients and Energy

Participants discussed recent findings regarding macronutrient and energy requirements during pregnancy and lactation, along with their relationships to maternal health and infant growth.

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• Omega-3 fatty acid supplementation during pregnancy does not appear to improve children’s neurodevelopment, especially if they’re born healthy and at term. It may, however, reduce the risk of premature birth, but likely only among women with low omega-3 status. Maternal omega-3 supplementation may also prolong gestation.
  Maria Makrides, SAHMRI Women and Kids Theme Leader, South Australian Health and Medical Research Institute
• Dietary Reference Intake estimates of protein needs during pregnancy may be underestimated. Protein needs also appear to increase over the course of pregnancy, although individual amino acid needs do not necessarily change at the same rate.
  Rajavel Elango, Associate Professor, The University of British Columbia School of Population and Public Health
• Women with obesity may not need to increase their energy intake during pregnancy.
  Leanne Redman, Professor, Louisiana State University Pennington Biomedical Research Center

Micronutrients, Nonnutritive Factors, and Dietary Supplements

The workshop included sessions that reviewed the current understanding of the roles and need for a variety of micronutrients and dietary supplements, and also explored nonnutritive factors.

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• Folic acid supplementation remains necessary for women of reproductive age to meet folate needs, even with mandated folate fortification of the food supply. However, a sizable percentage of pregnant women who use supplements have a total folic acid intake above the Tolerable Upper Intake Level.
  Yvonne Lamers, Associate Professor, Food, Nutrition and Health Program, The University of British Columbia School of Population and Public Health
• Fetal and infant development requires large amounts of choline. Higher maternal choline intake during pregnancy may improve certain aspects of children’s cognitive function.
  Marie Caudill, Professor, Division of Nutritional Sciences, Cornell University

• Pregnant women in the United States are considered mildly iodine deficient. Modest iodine deficiency during pregnancy is thought to effect children’s neurocognition. National and international professional groups recommended that pregnant women use a daily prenatal supplement containing 150 mg of iodine.
  Elizabeth Pearce, Professor, Boston University School of Medicine Section of Endocrinology, Diabetes, and Nutrition
• Most pregnant and lactating women in the United States use dietary supplements, but use varies by age, race and ethnicity, family income, and trimester of pregnancy. Although dietary supplements help meet the recommended targets for adequacy, they also contribute to potentially excessive intakes of certain nutrients, including iron and folic acid.
  Regan Bailey, Professor, Purdue University Department of Nutrition Science and Director, Indiana Clinical and Translational Sciences Institute, Purdue Nutrition Assessment Center

• The current thresholds and measures used to define anemia, iron deficiency, and iron-deficiency anemia during pregnancy merit reevaluation.
  Kimberly O’Brien, Professor, Division of Nutritional Sciences, Cornell University
• The number of caffeinated products available has expanded dramatically in the past 20 years. With a rapidly changing market, it is difficult to understand how these products are used. Pregnancy is one of many factors that affect caffeine metabolism, clearance, and pharmacokinetics.
  Janet Thorlton, Clinical Associate Professor, Department of Health Systems Science, Urbana Campus at the University of Illinois at Chicago College of Nursing

Human Milk and Lactation

Participants discussed the complex interplay between maternal nutrition, health, exposures, lactation, and the implications for maternal and infant health.

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• Some previous estimates of breast milk nutrient composition may have overestimated content, leading to Adequate Intake values for infants and lactating women that potentially exceed their needs.
  Lindsay H. Allen, Director, Western Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture
• Bidirectional relationships may exist between lactation and both maternal obesity and diabetes, but they may be confounded by metabolic status prior to and during pregnancy.
  Ellen Demerath, Professor of Epidemiology and Community Health, University of Minnesota School of Public Health

• Longer lactation duration and greater lactation intensity are associated with up to 50 percent lower risk of incident type 2 diabetes in women independent of metabolic status before conception or during pregnancy, obesity, and lifestyle factors. This lowering of risk has also been shown in women with gestational diabetes.
  Erica P. Gunderson, Epidemiologist and Senior Research Scientist, Kaiser Permanente Northern California Division of Research
• Human milk oligosaccharides serve as prebiotics that are not digested by the infant, but are digested by the microbes of the infant’s gut. Their concentrations in human milk are highly variable between women, are stable over the course of a day, and change over the course of lactation.
  Michael Goran, Professor of Pediatrics, Children’s Hospital Los Angeles and University of Southern California

Maternal Nutrient Intake and Early Life Programming

The workshop covered mothers’ intakes from the prenatal through postnatal periods and explored how nutrition during this period influences programming of the growth and development of their children.

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• Evidence from nonhuman primate models suggest the maternal imprint on her offspring’s microbiome is long lasting and potentially irreversible. Kjersti Aagaard, Professor and Henry and Emma Meyer Chair in Obstetrics and Gynecology, Baylor College of Medicine and Texas Children’s Hospital
• The placenta directs maternal metabolism and promotes fetal growth and development. It responds to changes in nutrient supply, which may developmentally program the fetus through epigenetic mechanisms. There are sexually dimorphic placental adaptations. Leslie Myatt, Professor of Obstetrics and Gynecology and Director of Perinatal Research, Moore Institute for Nutrition & Wellness, Oregon Health & Science University, Portland

Nutrition Access and Equity During Pregnancy and Lactation

Although evidence on relevant biological and physiological processes is fundamental to developing nutrition recommendations for women during pregnancy and lactation, dietary decisions and behaviors are made within structural, social, and environmental contexts. Workshop participants explored the role of systems and policies in improving nutrition access and equity during pregnancy and lactation.

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• Strong socioeconomic inequities, caused by social injustice, affect the health and nutrition of pregnant and lactating women. Inequities need to be addressed through systems approaches across the life course, based on implementation science.Rafael Pérez-Escamilla, Professor and Director of Global Health Concentration, Yale School of Public Health
• Fetal exposure to high maternal glucocorticoid concentrations is thought to be a key mechanism for how prenatal stress influences a child’s stress architecture. Nutrition has the potential to influence mental health, serve as a preventive intervention, and reduce health disparities.Kate Keenan, Professor of Psychiatry and Behavioral Neuroscience, University of Chicago
• Food insecurity is a major stress that is highly prevalent in the United States. Among both pregnant and nonpregnant populations, food insecurity has been found to be strongly associated with stress, depression, and anxiety.Barbara Laraia, Professor of Public Health Nutrition, University of California, Berkeley