Plant-based diet quality and cardiometabolic biomarkers in pregnant U.S. women

Abstract

Background: Evidence suggests that high-quality plant-based diets are associated with favorable cardiometabolic outcomes. However, there is no consensus on the optimal measure to assess the quality of plant-based diet. Furthermore, little is known about how plant-based diet quality relates to cardiometabolic health in pregnant women. Objective: Determine the relationship between plant-based diet and cardiometabolic biomarkers in pregnant women, with a specific focus on different approaches to assess plant-based diet quality. Methods: Data from 580 pregnant women who participated in seven cycles (2005 to 2020 prepandemic) of the National Health and Nutrition Examination Survey (NHANES) were used. Four previously established indices, including the overall Plant-Based Diet Index (PDI), healthful PDI (hPDI), total plant-based foods (All PBF), and Healthy PBF, were calculated. In addition, two modified indices were developed. Multivariable log-linear regression models were used to assess associations between these indices and cardiometabolic biomarkers. Results: Higher plant-based diet quality index values, independent of the index used, were positively associated with high-density lipoprotein cholesterol (HDL-C) concentrations, and negatively associated with triglyceride (TG)/HDL-C ratios. Each one-point increase in the diet index was associated with a 0.004 to 0.016 mg/dL increase in HDL-C and 0.018 to 0.031 decrease in TG/HDL-C ratio. Additionally, those indices that accounted for plant foods quality were also associated with lower fasting insulin and TG concentrations, and homeostatic model assessment for insulin resistance (HOMA-IR). Conclusions: In this NHANES cohort of pregnant women, higher values of all plant-based diet indices were associated with more favorable biomarkers of cardiometabolic health. Those plant-based diet indices that emphasized the quality of plant foods rather than penalizing the inclusion of animal foods were more strongly associated with cardiometabolic health biomarkers.

Keywords

Diet quality indices plant-based diets cardiometabolic biomarker insulin resistance U.S. pregnant women NHANES

Introduction

Evidence suggests that plant-based diets are associated with beneficial measures of cardiometabolic health, including lower risk of developing hypertension, systemic inflammation, type 2 diabetes, and cardiovascular disease (Banaszak et al., 2022; Glenn et al., 2024; Peña-Jorquera et al., 2023; Tonstad et al., 2013; Yokoyama et al., 2014). The new dietary guideline recommends increasing plant-based whole food intakes at the expense of red and processed meat (2025 Dietary Guidelines Advisory Committee, 2024).

However, not all plant-based diets are equivalent. Healthy plant-based diets rich in whole grain products, vegetables, fruits, nuts, and legumes are high in fiber, bioactive compounds (such as polyphenols and phenolic acids), essential nutrients and unsaturated fatty acids, and associated with positive cardiometabolic outcomes (Thomas et al., 2023). In contrast, unhealthy plant-based diets rich in refined grain products, such as cookies, pastries, and sugar-sweetened beverages, are associated with negative cardiometabolic outcomes.The latter dietary pattern is generally low in fiber and high in rapidly absorbable carbohydrate, resulting in a rapid rise in blood sugar and subsequent insulin concentrations (Beulens et al., 2007; Endy et al., 2024; Jackson et al., 2014; McKeown et al., 2010; Mozaffarian et al., 2011). These findings underscore the importance of evaluating the quality of food within plant-based diets.

There is no consensus on the optimal index to assess plant-based diet quality. Existing indices such as the overall Plant-Based Diet Index (PDI), healthful PDI (hPDI), total plant-based foods (All PBF), and Healthy PBF differ in how they classify plant and animal foods (Curlin et al., 2023; Jovanovic et al., 2023). As a result, studies using different indices limit inter-study comparisons and often resulted in inconsistent findings (Kent et al., 2022). There is a pressing need to identify plant-based diet indices that most accurately capture overall diet quality.

Despite the accumulating evidence supporting the value of healthful plant-based diets in promoting cardiometabolic health in the general population, limited research has examined these relationships in pregnant women, a group with unique hormonal and metabolic changes that increase susceptibility to insulin resistance and dyslipidemia (Salzer et al., 2015). Furthermore, there is no consensus on the optimal method to assess the quality of plant-based diets, and existing indices differ in handling plant and animal food components, often leading to inconsistent findings (Kent et al., 2022). To address these gaps, this study comprehensively evaluated the associations between multiple plant-based diet quality indices, including four established and two modified indices, and markers of cardiometabolic health in pregnant women. This study aimed to provide new insight into how plant-based diet quality can be best characterized in this population and its relevance to maternal cardiometabolic health.

Methods

Study sample

This study used data from seven cycles of the National Health and Nutrition Examination Survey (NHANES): 2005–2006, 2007–2008, 2009–2010, 2011–2012, 2013–2015, 2015–2016, and 2017 to 2020 pre-pandemic, to ensure adequate sample size and because these cycles contained the necessary dietary and biomarker data. Data from later NHANES cycles were not included in the analysis due to the absence of the required dietary information. NHANES is a national health survey that includes interviews, physical exams, laboratory tests, and dietary assessment to evaluate the health and nutritional status of adults and children in the United States (Centers for Disease Control and Prevention, 2025).

Pregnant women were identified through self-reported pregnancy and confirmed by a urine pregnancy test, conducted on all female participants aged 12–59 and menstruating females aged 8 to 11. Individuals with self-reported diabetes, hypertension, hypercholesterolemia, and those taking medications to treat hypertension, diabetes (insulin or other diabetic medications), or hypercholesterolemia at the time of the survey were excluded from the study. Participants with missing dietary data were also excluded from the analysis.

Demographic and dietary data

Demographic data, including age, race/ethnicity, education, and family income, were self-reported during in-person interviews. The ratio of family income to the poverty threshold defined by the U.S. Department of Health and Human Service was used as an indicator for family income, ranging from 0 (no income) to 5 (income ≥ 5 times of the federal poverty threshold) (Centers for Disease Control and Prevention, 2025).

The amount and type of foods consumed were estimated using the first-day 24-h dietary recall data recorded and calculated using the Food Patterns Equivalents Database (U.S. Department of Agriculture, 2025). Foods are disaggregated and their ingredients classifies into 37 food pattern components.

The components of the six plant-based diet indices are summarized in Table 1. The overall PDI assigns positive scores to all plant foods, and negative scores to animal foods. The hPDI further distinguished between healthy and unhealthy plant foods. Healthy plant foods (fruits, dark green vegetables, red and orange vegetables, starchy vegetables other than white potatoes, legumes, whole grains, soy, nuts and seeds, and plant oils) were scored positively, while unhealthy plant foods (fruit juice, white potatoes, refined grains, and added sugars) and animal foods (meat, poultry, seafood, eggs, and solid fats) were scored negatively (Curlin et al., 2023).

Table 1.

Components of plant-based diet indices.

	PDI	hPDI	All PBF	Healthy PBF	Modified all PBF	Modified healthy PBF
Intact fruits (whole or cut) (cup eq.)	+	+	+	+	+	+
Fruit juice (cup eq.)	+	−	+		+
Dark green vegetables	+	+	+	+	+	+
Red and orange vegetables	+	+	+	+	+	+
White potatoes	+	−	+	+	+
Other starchy vegetables	+	+	+	+	+	+
Other vegetables	+	+	+	+	+	+
Legumes (beans and peas)	+	+	+	+	+	+
Whole grains	+	+	+	+	+	+
Refined grains	+	−	+		+
Soy products—excluding soy milk	+	+	+	+	+	+
Nuts and seeds	+	+	+	+	+	+
Oils-mostly plant based		+	+		+	+
Added sugars		−	+
Meat/poultry/seafood	−	−
Eggs	−	−
Solid fats		−

Abbreviations: hPDI: healthful plant-based diet index; PBF: plant-based foods; PDI: plant-based diet index.

To calculate the PDI and hPDI, the intake of positive food groups was ranked into quintiles based on consumption (Curlin et al., 2023). Each quintile was assigned a score from 1 to 5, with the fifth quintile (highest consumption) receiving a score of 5 and the first quintile (lowest consumption) receiving a score of 1. Similarly, negative food groups were assigned scores in reverse: the fifth quintile (highest consumption) received a score of 1, and the first quintile (lowest consumption) received a score of 5. The scores of each food group were then summed to derive the PDI (possible range: 8–40) and the hPDI (18–90).

The All PBF only includes fruits (including fruit juice), vegetables, legumes, nuts and seeds, soy, grains (whole and refined), oils, and added sugars and does not consider animal-based foods (Jovanovic et al., 2023). The Healthy PBF is similar but excludes fruit juice, refined grains, added sugars, and oils (Jovanovic et al., 2023). Additionally, we developed the Modified All PBF by removing added sugars due to their high energy density and lack of fiber or essential nutrients; and Modified Healthy PBF by excluding white potatoes and including plant oils. Plant oils were added to the Modified Healthy PBF because they are rich in unsaturated fatty acids, particularly monounsaturated fats and polyunsaturated fats (PUFA), and some plant oils (such as extra virgin olive oil and flaxseed oil) also contain beneficial bioactive components including polyphenols, phytosterols, and the omega-3 fatty acid alpha-linolenic acid (Rosqvist and Niinistö, 2024).

The cardiometabolic biomarkers included fasting glucose, insulin, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglyceride (TG) concentrations, and TG/HDL-C ratio. The TG/HDL-C ratio was chosen rather than the TC/HDL-C ratio because it has been shown to be a stronger biomarker for diagnosing metabolic syndrome and cardiovascular disease compared to other lipid ratios (Abbasian et al., 2017; Gasevic et al., 2014; Kosmas et al., 2023). In addition, homeostatic model assessment for insulin resistance (HOMA-IR) was calculated as fasting insulin (mIU/L) × fasting glucose (mg/dL)/405 (Majid et al., 2017). Higher HOMA-IR values indicate greater insulin resistance.

Statistical analysis

Statistical analyses were performed using SAS Version 9.4 (SAS Institute). Dietary sampling weights were applied to account for the complex sampling design used in NHANES.

The Shapiro–Wilk test was used to assess the normality of cardiometabolic biomarkers. Skewed biomarkers were log-transformed and analyzed using log-linear regression. Multivariable regression analyses were further adjusted for sociodemographic covariates. Plant-based diet indices were analyzed as continuous variables in the regression models. To account for potential non-linear relationships, they were also examined as tertiles in the model, and the Jonckheere-Terpstra test was used to detect trend differences across tertiles. Total servings of the Modified All PBF and Modified Healthy PBF were also examined as a continuous variable in the log-linear regression models.

Missing values were addressed using a complete case approach. A P < 0.05 was considered statistically significant, with no adjustment for multiple testing.

Results

Characteristics of participants

Of 761 pregnant women identified, 621 had dietary information, of whom 580 had cardiometabolic biomarker data (Figure 1). Compared to women in the highest tertile of the hPDI (hPDI = 56–73), those in the lower tertiles (hPDI 36–49 or 50–55) were more likely to be younger (25.9 ± 5.0 years vs 29.0 ± 5.8 years; P < 0.001), less likely to be non-Hispanic white (26.5% vs 36.5%, P < 0.001), and have lower levels of education (28.3% vs 43.6% college and above degree, P < 0.001) and lower ratio of family income to the poverty threshold (1.81 ± 1.50 vs 2.77 ± 1.71, P < 0.001) (Table 2).

Figure 1.

Flow chart of participants selection.

Table 2.

Characteristics of participants by hPDI tertile: Mean ± SD or n (%).

Characteristics	Tertile of hPDI			P value
Characteristics	1 (N = 200)	2 (N = 210)	3 (N = 211)	P value
Age (y)	25.9 ± 5.0	26.8 ± 6.0	29.0 ± 5.8	<0.001
Race/ethnicity				<0.001
Non-Hispanic white	58 (26.5)	81 (37.0)	80 (36.5)
Non-Hispanic black	63 (51.6)	32 (26.2)	27 (22.1)
Mexican American	49 (29.5)	64 (38.6)	53 (31.9)
Other Hispanic ethnicity	20 (40.8)	14 (28.6)	15 (30.6)
Other race/ethnicity	10 (15.4)	19 (29.2)	36 (55.4)
Education				<0.001
Less than high school graduate	62 (41.3)	55 (36.7)	33 (22.0)
High school graduate	37 (31.6)	47 (40.2)	33 (28.2)
College and above	89 (28.3)	88 (28.0)	137 (43.6)
Ratio of family income to poverty	1.81 (1.50)	2.32 (1.61)	2.77 (1.71)	<0.001

Note: Values are mean ± SD for continuous variables and n (%) for categorical variables.

Abbreviations: hPDI: healthful plant-based diet index; SD: standard deviation.

When analyzed as continuous predictors of cardiometabolic biomarkers, higher values for all six plant-based diet indices were positively associated with HDL-C concentrations (each one-point increase in the diet index was associated with a 0.004 to 0.016 mg/dL increase in HDL-C; all P values < 0.01) and negatively associated with TG/HDL-C ratios (each one-point increase in the diet index was associated with a 0.018 to 0.031 decrease in TG/HDL-C ratio; all P values < 0.05) (Table 3).

Table 3.

Associations between intake of plant-based dietary patterns and cardiometabolic biomarkers^a.

	PDI	hPDI	All PBF	Healthy PBF	Modified all PBF	Modified healthy PBF
Fasting glucose (mg/dL)	0.001 (P = 0.650)	0.0003 (P = 0.749)	−0.001 (P = 0.570)	−0.002 (P = 0.268)	−0.001 (P = 0.475)	−0.002 (P = 0.389)
Fasting insulin (μU/mL)	−0.010 (P = 0.932)	−0.017 (P = 0.010)*	−0.009 (P = 0.403)	−0.021 (P = 0.033)*	−0.005 (P = 0.606)	−0.018 (P = 0.047)*
HOMA-IR	−0.0004 (P = 0.973)	−0.017 (P = 0.019)*	−0.010 (P = 0.382)	−0.023 (P = 0.035)*	−0.007 (P = 0.552)	−0.019 (P = 0.050)*
TC (mg/dL)	0.002 (P = 0.486)	−0.002 (P = 0.196)	0.004 (P = 0.155)	0.002 (P = 0.295)	0.004 (P = 0.124)	0.003 (P = 0.145)
LDL-C (mg/dL)	0.005 (P = 0.358)	−0.001 (P = 0.768)	0.002 (P = 0.697)	−0.0004 (P = 0.937)	−0.0002 (P = 0.978)	−0.003 (P = 0.569)
HDL-C(mg/dL)	0.010 (P < 0.001)**	0.004 (P = 0.005)**	0.016 (P < 0.001)**	0.011 (P < 0.001)**	0.016 (P < 0.001)**	0.013 (P < 0.001)**
TG (mg/dL)	−0.003 (P = 0.762)	−0.012 (P = 0.024)*	−0.014 (P = 0.098)	−0.013 (P = 0.098)	−0.014 (P = 0.092)	−0.017 (P = 0.012)*
TG/HDL-C ratio	−0.018 (P = 0.049)*	−0.018 (P = 0.001)**	−0.031 (P = 0.001)**	−0.025 (P = 0.003)**	−0.029 (P = 0.001)**	−0.029 (P < 0.001)**

Abbreviations: HDL-C: high-density lipoprotein cholesterol; HOMA-IR: homeostatic model assessment for insulin resistance; hPDI: healthful plant-based diet index; LDL-C: low-density lipoprotein cholesterol; PBF: plant-based foods; PDI: plant-based diet index; TC: total cholesterol; TG: triglyceride.

Regression coefficients adjusted for age, race/ethnicity, education, and the ratio of family income to the poverty threshold. Cardiometabolic biomarkers were log-transformed scales. *: P<0.05; **: P<0.01

Higher values for hPDI, healthy PBF, and modified Healthy PBF were also associated with lower fasting insulin (each one-point increase in the diet index was associated with 0.017 to 0.021 μU/mL decrease in fasting insulin) and HOMA-IR (−0.017 to −0.023). Furthermore, hPDI and modified healthy PBF were negatively associated with fasting TG concentrations (−0.012 to −0.017 mg/dL).

When examined as tertiles, of the indices that accounted for plant-based diet quality by distinguishing between “healthy” and “unhealthy” plant foods (hPDI, Healthy PBF and Modified Health PBF indices), the highest hPDI tertile was associated with lower fasting insulin concentrations (10.9 μU/mL) and HOMA-IR (2.4) compared to the lowest tertile (12.5 μU/mL and 2.7, respectively; P for trend < 0.05, Table 4).

Table 4.

Cardiometabolic biomarkers by tertiles of hPDI, healthy PBF, and modified healthy PBF.^a

	hPDI			P for trend	Healthy PBF			P for trend	Modified healthy PBF			P for trend
	1	2	3	P for trend	1	2	3	P for trend	1	2	3	P for trend
Fasting glucose (mg/dL)	88	86	90	0.280	90	87	87	0 . 016*	88	89	86	0.197
Fasting insulin (μU/mL)	12.5	10.1	10.9	0 . 021*	12.5	11.2	10.3	0.458	11.4	13.7	8.8	0 . 002**
HOMA-IR	2.7	2.2	2.4	0 . 020*	2.8	2.4	2.2	0.356	2.5	3.0	1.9	0 . 002**
TC (mg/dL)	214	207	207	0.375	204	214	211	0 . 042*	210	202	221	0 . 006**
LDL-C (mg/dL)	110	96	97	0.421	105	103	97	0.244	102	96	106	0.275
HDL-C(mg/dL)	65	63	69	0.067	62	65	72	<0 . 001**	61	65	71	<0 . 001**
TG (mg/dL)	143	113	108	0.277	130	132	104	0 . 002**	127	131	108	0.103
TG/HDL-C ratio	2.3	1.8	1.6	0.392	2.1	2.1	1.5	0 . 022*	2.1	2.0	1.6	0 . 007**

Abbreviations: HDL-C: high- density lipoprotein cholesterol; HOMA-IR: homeostatic model assessment for insulin resistance; hPDI: healthful plant-based diet index; LDL-C: low-density lipoprotein cholesterol; PBF: plant-based foods; TC: total cholesterol; TG: triglyceride.

Adjusted for age, race/ethnicity, education, and the ratio of family income to the poverty threshold. *: P<0.05; **: P<0.01

The highest tertile of Healthy PBF was associated with lower fasting glucose (87 mg/dL) and TG (104 mg/dL) concentrations, and TG/HDL-C ratio (1.5), as well as higher HDL-C concentrations (72 mg/dL; P for trend < 0.05, Table 4).

The highest tertile of Modified Healthy PBF was associated with lower fasting insulin concentrations (8.8 μU/mL), HOMA-IR (1.9), TG/HDL-C ratio (1.6), and higher HDL-C concentrations (71 mg/dL; P for trend < 0.05, Table 4).

Discussion

This study provides insights into the association between plant-based diet quality indices and cardiometabolic health in the U.S. pregnant women. We found that higher adherence to all six plant-based diets was consistently associated with more favorable cardiometabolic biomarkers, and those who adhered to the healthier plant-based diets have the most favorable cardiometabolic biomarkers. Indices that emphasized the quality of plant foods rather than penalizing animal foods showed the strongest associations, suggesting that plant food quality may be more critical than simply limiting animal foods during pregnancy. To our knowledge, this study is among the first to compare multiple plant-based diet quality indices, including four established and two modified versions, to identify which best capture diet quality in pregnant women.

Of the six plant-based diet quality indices calculated, two included both plant and animal foods: the overall PDI, which assigns positive scores to all plant foods and negative scores to animal foods; and the hPDI, which assigns positive scores to healthful plant foods and negative scores to unhealthful plant foods and all animal foods (Curlin et al., 2023). Higher overall PDI values were positively associated with HDL-C concentrations and negatively associated with TG/HDL-C ratio, indicating a favorable lipid profile in women consuming more plant-based foods during pregnancy. The hPDI was also associated with lower fasting insulin, HOMA-IR, and TG concentrations. This may be attributed to the higher fiber content and unsaturated/saturated fat ratio of these diets. The observed negative association between hPDI and fasting insulin aligns with findings from previous studies (Curlin et al., 2023).

The remaining four PBF indices consider plant-based foods only. The All PBF index includes total plant food intake, while the Healthy PBF index excludes fruit juice, refined grains, added sugars, and oils (Jovanovic et al., 2023). Oils were excluded from the Healthy PBF index because it was based on the NOVA classification system, which categorizes oils made from seeds, nuts, and fruits as “processed culinary ingredients,” and coconut oil as “processed foods” (Monteiro et al., 2018). Consistent with findings from the overall PDI and hPDI, higher All PBF values were associated with higher HDL-C concentrations and lower TG/HDL-C ratio, while the Healthy PBF index showed associations with additional cardiometabolic biomarkers including fasting insulin and HOMA-IR. Interestingly, the Healthy PBF index, which does not assign negative scores to animal foods, resulted in a stronger effect size than the hPDI, which penalizes animal food intake. This suggests that emphasizing the quality of plant foods may be more important for cardiometabolic health in pregnancy than penalizing animal food consumption.

We calculated two modified versions of the plant-based diet indices: the Modified All PBF, which excludes added sugars because they provide excess calories without contributing fiber or essential micronutrients, and the Modified Healthy PBF, which further excludes white potatoes. Similar to the results observed with the other indices, the Modified All PBF was associated with higher HDL-C concentrations and TG/HDL-C ratio, while the Modified Healthy PBF was also associated with lower fasting insulin and TG concentrations, and HOMA-IR.

Our results are largely consistent with prior studies in nonpregnant adults, which have shown that higher adherence to healthful plant-based diets is linked to lower fasting insulin, improved HOMA-IR, higher HDL-C, and lower TG/HDL-C ratios (Austin et al., 2024; Rosenfeld et al., 2023). Notably, plant-based diet quality indices that account for the quality of plant foods showed stronger associations with incident cardiovascular disease risk than generic or unhealthful plant-based diet indices (Quek et al., 2021; Wang et al., 2024). In the Nurses’ Health Study, higher adherence to PDI was associated with lower risk of coronary heart disease, whereas higher hPDI scores were linked to an even greater reduction in risk, and the unhealthy PDI was associated with increased risk, highlighting the importance of plant food quality over simple plant food quantity (Satija et al., 2017). We did not observe a significant association between plant-based diet indices and LDL-C concentrations as has been reported previously (Austin et al., 2024; Polesel et al., 2024; Trautwein and McKay, 2020). This was not unexpected, given our study subpopulation was relatively young and healthy, with mean LDL-C concentrations within normal limits.

The observed association between cardiometabolic biomarkers with the plant-based diet quality indices may be partly explained by the nutrient composition of the diets captured by these indices. The common features of healthy plant-based dietary patterns include whole grains, fruits, vegetables, nuts and legumes. These foods are rich in dietary fiber which is a contributor to modulating lipid profiles and glucose and insulin homeostasis (Fu et al., 2022). Fiber also supports a healthy gut microbiota, particularly those associated with reduced systemic inflammation (Ma et al., 2021; Wastyk et al., 2021).

The strengths of this study include the evaluation of a broad range of plant-based diet quality indices, including previously established ones (PDI, hPDI, All PBF, Healthy PBF) and two modified versions. The consistent associations observed across multiple indices strengthen the validity of the findings and underscore the robustness of the relationship between plant-based diet quality and cardiometabolic health, in this understudied subgroup of the population, pregnant women.

In terms of study limitations, we only included the first-day 24-h dietary recall due to a significant number of missing data for the second day's dietary data. Although age, education, race/ethnicity, and family income were adjusted for in analyses, there may be residual confounders that could influence the associations identified. We were unable to adjust for the pregnancy stage.

In summary, this study found that in pregnant women, while all plant-based diets were associated with favorable cardiometabolic markers, stronger associations were observed for healthier plant-based diets characterized by high fiber content, wholesome plant foods, and lower consumption of refined grains and added sugars. Those plant-based diet indices that emphasized the quality of plant foods rather than penalizing inclusion of animal foods had the strongest association with cardiometabolic health biomarkers.

Footnotes

ORCID iD

Ling Shi

Ethical considerations

This study does not require IRB approval, as it is a secondary analysis of publicly available data from the NHANES which are deidentified and released for public use in compliance with ethical and regulatory standards.

Consent to participate

Participants in NHANES provide informed consent to voluntarily take part in interviews, physical exams, and laboratory testing.

Consent for publication

Not applicable.

Author contributions

LS designed the research, analyzed the data, wrote the manuscript, and edited the manuscript. AHL contributed to the discussion and reviewed/edited the manuscript. LLH contributed to the discussion and reviewed/edited the manuscript. LS had primary responsibility for the final content. All authors read and approved the manuscript.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data availability

The NHANES data are publicly accessible and available for download from the Centers for Disease Control and Prevention (CDC) website at .

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