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Introduction

The National Academies of Sciences, Engineering, and Medicine last reviewed the state of the science on nutrition during pregnancy and lactation 30 years ago. The resulting consensus study reports from the Institute of Medicine—Nutrition During Pregnancy (IOM, 1990) and Nutrition During Lactation (IOM, 1991)—summarized the scientific evidence and provided nutrient recommendations. In the decades since the release of these two reports, the body of evidence on the relationships between nutrition during pregnancy and lactation and maternal and infant health and chronic disease has continued to grow and evolve. At the same time, the demographics of the population have shifted, giving rise to new considerations. To explore the evidence that has emerged, an ad hoc planning committee was asked to plan a 2-day workshop (see Box 1-1). The workshop was held January 29–30, 2020, in Washington, DC.¹

SETTING THE STAGE FOR THE WORKSHOP

In her welcoming remarks, Anna Maria Siega-Riz, dean and professor in the School of Public Health & Health Sciences at the University of Massachusetts Amherst and chair of the workshop planning committee,

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¹ The planning committee’s role was limited to planning the workshop and the Proceedings of a Workshop was prepared by the rapporteur as a factual account of what occurred at the workshop. Statements, recommendations, and opinions expressed are those of individual presenters and participants and are not necessarily endorsed or verified by the National Academies of Sciences, Engineering, and Medicine. They should not be construed as reflecting any group consensus.

highlighted some of the key findings from the two previous consensus reports. In Nutrition During Pregnancy (IOM, 1990), iron was identified as the only known nutrient for which supplementation was needed to fill the gap between dietary intake and requirements, although questions were raised at that time about the adequacy of calcium and vitamin D intake among women younger than 25 years of age. By comparison, the report found that folate requirements could be met through dietary intake alone. Siega-Riz noted that the report cautioned against the use of preformed vitamin A supplements during the first trimester and discouraged the use high-protein supplements during pregnancy. Available evidence on the effects of coffee or caffeine intake were described as “inconsistent and fragmentary,” she said. Nutrition During Lactation (IOM, 1991) concluded that women in the United States are capable of fully nourishing their infants through breastfeeding and recommended that, under ordinary circumstances, all infants should be breastfed. The report found that “data [were] lacking for use in developing strategies to identify lactating women who are at risk of depleting their own nutrient stores” (IOM, 1991, p. 11).

Shifts in the demographics and health of the population that have taken place over the past 30 years have implications for nutrition and dietary recommendations during pregnancy and lactation, indicated Siega-Riz. Maternal age at first birth has increased over time, whereas birth rates among teenagers have declined. The proportion of women who smoke during pregnancy has decreased over time, which Siega-Riz thought was promising, as smoking contributes to low birth weight. Over the same period, the prevalence of prepregnancy overweight and obesity has increased, coupled with corresponding increases in diabetes among U.S. mothers. “What you

are seeing is older women, heavier women, and women with a greater risk of having diabetes becoming pregnant,” said Siega-Riz.

Remarking on changes in the dietary intake of the population, Siega-Riz noted that at any given time, one-third of U.S. adults report following a special diet (e.g., intermittent fasting, paleo, ketogenic) (IFIC Foundation, 2018), and that women are now more likely to enter pregnancy with such intakes. Consumers are also factoring in food labels as they make decisions about what to eat (IFIC Foundation, 2018). From her own work, Siega-Riz found that pregnant women are interested in knowing more about the diets they should be consuming, including whether they should be eating organic foods and a sustainable diet. She commented that the landscape of where consumers shop and purchase foods and beverages is changing, and the wide availability of food affects what foods pregnant and lactating women access.

Siega-Riz summarized her remarks by saying, “There has been a huge shift not only in the types of diets that individuals are following, [but also in] our food supply and the demand for what types of foods women should be consuming.” She also noted that the expansion of the Dietary Reference Intake model to include a new category of values based on chronic disease risk reduction merits further consideration for the type of evidence that needs to be gathered for these life stages. Given the changes in the scientific evidence, demographics, and nutritional landscape, Siega-Riz contended that Nutrition During Pregnancy and Nutrition During Lactation are now out of date and efforts are needed to provide current evidence to inform practitioners and women.

SPONSOR REMARKS

To open her comments, Nancy Potischman, director of the Population Studies Program at the Office of Dietary Supplements (ODS), explained that ODS operates somewhat differently than other offices or institutes within the National Institutes of Health, in that it is not restricted to studying a specific age group or set of conditions or outcomes. Rather, ODS’s mission is to “strengthen knowledge and understanding of dietary supplements,” said Potischman. To achieve this mission, ODS’s goals include stimulating and supporting research on dietary supplements, supporting the development of research tools, evaluating scientific findings, and making current knowledge on dietary supplements available to the public. Potischman shared a few examples of questions ODS received from the public, clinicians, and the media. For instance, health care providers contacted ODS wanting to know the appropriate folate dose and the safety of 5-methyltetrahydrofolate (5-MTHF) for pregnant women with mutations in the methylenetetrahydrofolate reductase (MTHFR) gene. Another query

ODS received asked about the lower iron recommendation for women who are breastfeeding compared to women who are not. Potischman saw the workshop as an opportunity to learn more about dietary issues broadly, in addition to exploring nutritional status and dietary supplement use.

Next, Heather McMillan, nutrition officer at the Office of Nutrition Policy and Promotion at Health Canada, spoke about her agency’s interest in the workshop. Health Canada is the federal department responsible for helping maintain and improve the health of Canadians. McMillan highlighted some of the work Health Canada has done related to nutrition, including developing and promoting dietary guidance; developing nutrition labeling and claims policies and regulations; and conducting nutrition surveillance, research, and data analysis. Additionally, Health Canada has published prenatal nutrition guidelines that are widely used by health professionals in various settings. McMillan thought the workshop could help to identify knowledge gaps, which, if filled, may inform future policies.

Following McMillan’s remarks, Alison Steiber, chief science officer in research, international, and scientific affairs for the Academy of Nutrition and Dietetics (the Academy), provided some background on her organization. She explained that the Academy is the largest organization of credentialed nutrition professionals in the world. During its centennial in 2017, the Academy revised its vision statement to “a world where all people thrive through the transformative power of food and nutrition,” and it revised its mission statement to “to accelerate improvements in global health and well-being through food and nutrition.” Steiber indicated that the topics covered by the workshop are well aligned with the Academy’s vision and mission statements. For instance, the Academy seeks to improve the health of women before and during early pregnancy to affect the health of their children. She also noted that the Academy is striving to increase support and scientific evidence related to breastfeeding, to help women achieve the duration appropriate for them and to better understand relationships with health outcomes. Steiber described a recently launched project looking at how registered dietitian nutritionists work with pregnant and lactating women and the associated maternal and infant outcomes. Furthermore, the Academy has an interest in regulations, including those related to labeling donor milk and medical nutrition therapy for pregnant and lactating women. Steiber closed her remarks by highlighting recent systematic reviews from her organization (e.g., malnutrition in pregnancy [Pari-Keener et al., 2020], effect of bariatric surgery on maternal and infant outcomes [Al-Nimr et al., 2019]) and suggested that the workshop could inspire additional rigorous work in the field.

ORGANIZATION OF THE PROCEEDINGS

The chapters that follow this introductory chapter summarize the presentations and discussions on nutrition during pregnancy and lactation that took place over the course of the 2-day workshop. Chapter 2 focuses on new evidence that has emerged on macronutrient requirements and quality to support optimal maternal health and fetal growth. Chapter 3 provides an overview of folate, synthetic folic acid, vitamin B12, and choline as micronutrients with key roles in one-carbon metabolism. Chapter 4 reviews the state of the science on iron, vitamin D, calcium, antioxidants, and iodine. Chapter 5 explores the role of optimal dietary supplement use and bioavailability of different formulations. Chapter 6 outlines select topic areas where there have been new or emerging scientific developments. Chapter 7 summarizes current evidence on maternal nutritional and metabolic health status and the implications for breast milk composition, lactogenesis, and maternal chronic disease risk. Chapter 8 reviews the role of maternal intake on early-life programming. Chapter 9 explores the individual-, systems-, and population-level interventions that provide solutions to issues of nutrition access and equity. Chapter 10 includes reflections on the workshop. Acronyms and abbreviations are listed in Appendix A, the workshop agenda is provided in Appendix B, and speaker and moderator biographical sketches are presented in Appendix C.

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