Background:

1. This important public health question was identified by the U.S. Departments of Agriculture (USDA) and Health and Human Services (HHS) to be examined by the 2020 Dietary Guidelines Advisory Committee.

2. The 2020 Dietary Guidelines Advisory Committee, Pregnancy and Lactation Subcommittee conducted a systematic review to answer this question with support from the Nutrition Evidence Systematic Review (NESR) team.

3. The goal of this systematic review was to examine the following question: What is the relationship between maternal diet during pregnancy and lactation and risk of child food allergies and atopic allergic diseases?

Conclusion statements and grades:

1. Food allergy

   1. Pregnancy

      1. Insufficient evidence is available to determine the relationship between lower or restricted consumption of cow milk products during pregnancy only, or during both pregnancy and lactation, and risk of food allergy in the child. (Grade: Grade not assignable)

      2. Insufficient evidence is available to determine the relationship between peanuts, eggs, or wheat consumed during pregnancy and risk of food allergy in the child. (Grade: Grade not assignable)

      3. Limited evidence suggests no relationship between soybean consumed during pregnancy and risk of food allergy in the child. (Grade: Limited)

      4. No evidence is available to determine the relationship between maternal dietary patterns or fish, tree nuts and seeds, and foods not commonly considered to be allergens, such as meat, vegetables, and fruits consumed during pregnancy and risk of food allergy in the child. (Grade: Grade not assignable)

   2. Lactation

      1. Insufficient evidence is available to determine the relationship between lower or restricted consumption of cow milk products during both pregnancy and lactation and risk of food allergy in the child. (Grade: Grade not assignable)

      2. No evidence is available to determine the relationship between maternal dietary patterns or cow milk products, eggs, peanuts, soybean, wheat, fish, tree nuts and seeds, and foods not commonly considered to be allergens, such as meat, vegetables, and fruits consumed during lactation and risk of food allergy in the child. (Grade: Grade not assignable)

2. Atopic dermatitis/eczema

   1. Pregnancy

      1. Moderate evidence indicates that lower or restricted consumption of cow milk products during pregnancy does not reduce the risk of atopic dermatitis/eczema in the child. (Grade: Moderate)

      2. Moderate evidence indicates that lower or restricted consumption of egg during pregnancy does not reduce the risk of atopic dermatitis/eczema in the child. (Grade: Moderate)

      3. Insufficient evidence is available to determine the relationship between cow milk products and eggs restricted during both pregnancy and lactation and risk of atopic dermatitis/eczema in the child. (Grade: Grade not assignable)

      4. Limited evidence suggests that fish consumed during pregnancy does not increase the risk of atopic dermatitis/eczema in the child. (Grade: Limited)

      5. Limited evidence suggests that dietary patterns during pregnancy are not associated with risk of atopic dermatitis/eczema in the child. (Grade: Limited)

      6. Insufficient evidence is available to determine the relationship between peanuts, soybean, wheat/cereal, yogurt and probiotic milk products, and foods not commonly considered to be allergens, such as meat, vegetables, and fruits, consumed during pregnancy and risk of atopic dermatitis/eczema in the child. (Grade: Grade not assignable)

      7. No evidence is available to determine the relationship between tree nuts and seeds consumed during pregnancy and risk of atopic dermatitis/eczema in the child. (Grade: Grade not assignable)

   2. Lactation

      1. Insufficient evidence is available to determine the relationship between cow milk products restricted during both pregnancy and lactation, or during lactation only, and risk of atopic dermatitis/eczema in the child. (Grade: Grade not assignable)

      2. Insufficient evidence is available to determine the relationship between egg consumption restricted during both pregnancy and lactation and risk of atopic dermatitis/eczema in the child. (Grade: Grade not assignable)

      3. No evidence is available to determine the relationship between maternal dietary patterns or yogurt and probiotic milk products, eggs, fish, peanuts, tree nuts and seeds, soybean, wheat/cereal, and foods not commonly considered to be allergens, such as meat, vegetables, and fruits, consumed during lactation and risk of atopic dermatitis/eczema in the child. (Grade: Grade not assignable)

3. Allergic rhinitis

   1. Pregnancy

      1. Insufficient evidence is available to determine the relationship between cow milk products (fermented or non-fermented) consumed during pregnancy only, or during both pregnancy and lactation, and risk of allergic rhinitis in the child. (Grade: Grade not assignable)

      2. Moderate evidence indicates that lower or restricted consumption of eggs during pregnancy does not reduce the risk of allergic rhinitis in the child. (Grade: Moderate)

      3. Limited evidence suggests that dietary patterns during pregnancy are not associated with risk of allergic rhinitis in the child. (Grade: Limited)

      4. Insufficient evidence is available to determine the relationship between fish, peanuts, tree nuts, soybean, wheat, and foods not commonly considered to be allergens, such as meat, vegetables, and fruits consumed during pregnancy and risk of allergic rhinitis in the child. (Grade: Grade not assignable)

      5. No evidence is available to determine the relationship between seeds consumed during pregnancy and the risk of allergic rhinitis in the child. (Grade: Grade not assignable)

   2. Lactation

      1. Insufficient evidence is available to determine the relationship between cow milk products consumed during both pregnancy and lactation, and risk of allergic rhinitis in the child. (Grade: Grade not assignable)

      2. No evidence is available to determine the relationship between maternal dietary patterns or cow milk products, eggs, fish, peanuts, tree nuts and seeds, soybean, wheat, and foods not commonly considered to be allergens, such as meat, vegetables, and fruits consumed during lactation and risk of allergic rhinitis in the child. (Grade: Grade not assignable)

4. Asthma

   1. Pregnancy

      1. Limited evidence suggests that a lower consumption of cow milk products during pregnancy does not reduce risk of asthma in the child. (Grade: Limited)

      2. Insufficient evidence is available to determine the relationship between cow milk products consumed during both pregnancy and lactation and risk of asthma in the child. (Grade: Grade not assignable)

      3. Limited evidence suggests no relationship between eggs consumed during pregnancy and risk of asthma in the child. (Grade: Limited)

      4. Limited evidence suggests no relationship between fish consumed during pregnancy and risk of asthma in the child. (Grade: Limited)

      5. Insufficient evidence is available to determine the relationship between maternal dietary patterns or peanuts, tree nuts, soybean, and other foods such as wheat/whole grains, vegetables, fruits, beverages, and margarine consumed during pregnancy and risk of asthma in the child. (Grade: Grade not assignable)

      6. No evidence is available to determine the relationship between seeds consumed during pregnancy and risk of asthma in the child. (Grade: Grade not assignable)

   2. Lactation

      1. Insufficient evidence is available to determine the relationship between cow milk products consumed during both pregnancy and lactation, or during lactation only, and risk of asthma in the child. (Grade: Grade not assignable)

      2. Insufficient evidence is available to determine the relationship between fish, and other foods, such as margarine, oil, butter and butter-spreads, meat, and meat products consumed during lactation and risk of asthma in the child. (Grade: Grade not assignable)

      3. No evidence is available to determine the relationship between maternal dietary patterns or eggs, peanuts, wheat, tree nuts and seeds, and soybean consumed during lactation and risk of asthma in the child. (Grade: Grade not assignable)

Methods:

1. A literature search was conducted using four databases (PubMed, Cochrane, Embase, and CINAHL) to identify articles that evaluated the intervention or exposure of maternal diet during pregnancy and lactation and the outcomes of child food allergies and atopic allergic diseases. A manual search was conducted to identify articles that may not have been included in the electronic databases searched. Articles were screened by two NESR analysts independently for inclusion based on pre-determined criteria.

2. Data extraction and risk of bias assessment were conducted for each included study, and both were checked for accuracy. The Committee qualitatively synthesized the body of evidence to inform development of a conclusion statement(s), and graded the strength of evidence using pre-established criteria for risk of bias, consistency, directness, precision, and generalizability.

Summary of the evidence:

1. Pregnancy

   1. This systematic review included 36 articles from five randomized controlled trials (RCTs), one non-RCT (NRCT), and 13 prospective cohort studies that assessed the association between maternal diet and risk of food allergy, atopic dermatitis/eczema, allergic rhinitis, and asthma in the child occurring from birth through 18 y of age. The articles were published between 1987 and 2020 and consisted of:

      1. ○

         Thirty articles from 15 studies that included only pregnant women.

      2. ○

         Six articles from four studies that included both pregnant and lactating women.

   2. Six articles from two RCTs and two prospective cohort studies examined maternal avoidance and/or consumption of cow milk products, eggs, soybean, wheat, and peanuts during pregnancy alone, or during both pregnancy and lactation, in relation to risk of food allergy in the child from birth through 18 y of age.

   3. Twenty-five articles from five RCTs, one NRCT, and 10 prospective cohort studies examined maternal dietary patterns and consumption and/or avoidance of cow milk products, eggs, fish, soybean, wheat, peanuts, tree nuts, and other foods not commonly considered to be allergens during pregnancy alone, or during both pregnancy and lactation, in relation to risk of atopic dermatitis/eczema in the child from birth through age 18 y.

   4. Sixteen articles from four RCTs and six prospective cohort studies examined maternal dietary patterns and avoidance and/or consumption of cow milk products, eggs, fish, soybean, wheat, peanuts, tree nuts, and other foods not commonly considered to be allergens during pregnancy alone, or during both pregnancy and lactation, in relation to risk of allergic rhinitis in the child from birth through 18 y of age.

   5. Nineteen articles from two RCTs and eight prospective cohort studies examined maternal dietary patterns and avoidance and/or consumption of cow milk products, eggs, fish, soybean, peanuts, tree nuts, and other foods during pregnancy alone, or during both pregnancy and lactation, in relation to risk of asthma in the child from 2 through 18 y of age.

   6. No articles were identified that examined maternal consumption of seeds during pregnancy in relation to risk of atopic outcomes in the child from birth through 18 y of age.

   7. The ability to draw strong conclusions was limited by the following issues:

      1. ○

         Few RCTs have been conducted and thus, data were primarily observational in nature, limiting the ability to determine causal effects of consumption or avoidance of different foods during pregnancy and risk of atopic dermatitis, food allergies, allergic rhinitis, and asthma in the child.

      2. ○

         Key confounders were not consistently controlled for in most of the studies.

      3. ○

         Studies had risk-of-bias issues, such as self-reported outcomes and selection bias.

      4. ○

         People with lower SES, adolescents, and racially and ethnically diverse populations were underrepresented in the body of evidence.

2. Lactation

   1. This systematic review included eight articles from four randomized controlled trials (RCTs), one non-RCT (NRCT), and one prospective cohort study that assessed the relationship between maternal diet during both pregnancy and lactation, or during lactation alone, and risk of food allergy, atopic dermatitis/eczema, allergic rhinitis, and asthma in the child occurring from birth through 18 y of age. The included articles were published between 1989 and 2013.

      1. ○

         Six articles from four studies included both pregnant and lactating women.

      2. ○

         Two studies included only lactating women.

   2. Four articles from two RCTs examined maternal avoidance of cow milk products, eggs, soybean, wheat, and peanuts during both pregnancy and lactation, in relation to risk of food allergy and allergic rhinitis in the child from birth through 18 y of age. None of these studies were conducted exclusively in lactating women.

   3. Seven articles from four RCTs and one NRCT examined maternal avoidance of cow milk products, eggs, soybean, wheat, and peanuts during both pregnancy and lactation, or during lactation alone, in relation to the risk of atopic dermatitis/eczema in the child from birth through 18 y of age. Of these, only one RCT was conducted exclusively in lactating women.

   4. Four articles from two RCTs and one prospective cohort study examined maternal avoidance and/or consumption of cow milk products, eggs, fish, soybean, peanuts, wheat, and other foods during both pregnancy and lactation, or during lactation alone, in relation to risk of asthma in the child from 2 through 18 y of age. Of these, one prospective cohort study was conducted exclusively in lactating women.

   5. No articles were identified that examined maternal avoidance or consumption of seeds during lactation in relation to the risk of atopic outcomes in the child from birth through 18 y of age.

   6. The ability to draw strong conclusions was limited by the following issues:

      1. ○

         Very few studies assessed the relationship between maternal diet during lactation alone and risk of atopic dermatitis, food allergy, allergic rhinitis, and asthma.

      2. ○

         Key confounders were not consistently controlled for in most of the studies.

      3. ○

         Women with lower socioeconomic status (SES), adolescents, and racially and ethnically diverse populations were underrepresented in the body of evidence.