Nutrition literacy in pregnant women: a systematic review

Introduction

Nutrition literacy can be defined as possessing the skills and knowledge to make informed decisions about food choices that can impact one’s health [1]. Not only does this include the ability to pick nutrient-rich food over nutrient scarce options, nutrition literacy also includes an understanding of how food choices impact an individual’s health [2]. Furthermore, nutrition literacy incorporates the abilities to both seek out and sort through reliable nutrition resources [3]. Nutrition literacy is an inherently important concept, but also a broadly global issue, as people of all ages, socioeconomic, and cultural backgrounds are affected [1]. But this breadth may create additional challenges, where either people are bombarded with too much information and may not know how to synthesize it, or individuals lack access to understandable resources to make knowledgeable decisions [1]. Further, with increasing obesity and chronic disease rates in today’s society, emphasizing nutrition literacy is of utmost importance [2].

Many studies have shown that nutrition literacy plays an important role in establishing healthy diet patterns that impact an individual’s overall health [3]. Evidence has shown that even a basic level of nutrition literacy is positively associated with food selection, eating habits, and diet quality [3], 4]. Expanding on this, poor nutrition literacy translates to poor diet patterns that can negatively impact one’s health [4]. Several studies have linked poor nutrient intake and diet patterns to increased risk of diabetes mellitus, cardiovascular disease [5], 6], and the development and pathogenesis of autoimmune conditions such as rheumatoid arthritis and thyroid disease [7], 8]. Nutrition impacts a broad spectrum of disease conditions; therefore, improving nutrition literacy has the potential to positively impact many disease outcomes. Nutrition literacy is a foundational skill that not only impacts personal health outcomes, but also influences future generations, particularly among vulnerable populations such as pregnant women.

When it comes to nutrition, pregnant women have additional unique dietary requirements essential for their own health as well as their children’s development (which can extend well into adulthood) [9], 10]. To support the cellular and metabolic activities that occur during pregnancy, it is recommended that pregnant women eat a balanced diet with adequate intakes of micronutrients, such as calcium, iron, magnesium, folate, iodine, zinc, vitamin D, vitamin A, and omega-3 fatty acids [9]. Many pregnant women suffer nutritional deficiencies such as iron and vitamin D during pregnancy, and these deficiencies can be exacerbated even more during adolescent pregnancies when the mother must support both the fetus and their own growth [9], 11]. Folic acid is an especially important nutrient during pregnancy as it helps prevent neural tube defects; however, deficiency of this nutrient is also common in pregnancy, and supplementation in the periconceptional period (eight weeks before and eight weeks after conception) is recommended by the World Health Organization [9]. Additionally, following the recommended weight gain guidelines during pregnancy, which are based on an individual’s pre-pregnancy body mass index (BMI), is important for supporting optimal health outcomes for both mother and child [9]. Navigating these nutritional requirements can be difficult for pregnant women without a foundational understanding of nutrition literacy. Therefore, understanding nutrition literacy levels in pregnant females could help improve health outcomes for women and their unborn children during this important period of time.

The aim of this systematic review is to evaluate how socioeconomic factors and nutrition education interventions impact nutrition literacy among pregnant women. This review will synthesize the existing literature to identify gaps in knowledge and recommend targeted strategies to improve nutrition literacy. While many studies explore the broad topics of nutrition knowledge, attitudes, and practices, this review focuses specifically on research that evaluates nutrition literacy levels as a critical determinant of health outcomes during pregnancy.

Methods

Results

The initial search yielded a total of 3,715 articles. After the removal of 1,958 duplicates, a total of 1,757 articles remained for screening. These records were imported into Covidence, a systematic review management platform, to facilitate initial screening and collaboration. During title and abstract screening, 1,703 articles were excluded as they did not meet the predefined inclusion criteria. Following the initial screening, the full-text of 54 articles was reviewed for eligibility by both authors and disagreements were resolved through discussion. After this was completed, 5 of the identified articles met the inclusion criteria of nutrition literacy among pregnant women. (See Figure 1). Reasons for exclusion were documented, and a Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) flowchart was used to illustrate the selection process (see Table 1).

Figure 1:

PRISMA diagram.

Five studies focused on nutrition literacy in pregnancy [10], [12], [13], [14], [15]. Papežová and colleagues explored nutrition literacy among 401 pregnant women in the Czech Republic using a newly created instrument called the Nutrition Knowledge Test (NKT) to conduct their cross-sectional study [10]. The authors reported that only 5 % of the participants achieved an overall nutrition literacy score of 80 % or more (which indicated a satisfactory level of nutrition knowledge). Their findings suggested that several factors impacted the scores positively, including university education, residence in the capital city, first pregnancy, having a normal or overweight status, and having a chronic noncommunicable disease. They found participants had the lowest knowledge areas in regards to optimal energy intake during pregnancy, optimal weight gain during pregnancy, and the role of micronutrients in the diet during pregnancy.

Camargo et al. assessed the level of nutrition literacy among 112 pregnant Latina/x individuals in the United States [12]. Their cross-sectional study utilized the Nutrition Literacy Assessment Instrument (NLit) and they reported that most participants demonstrated low nutrition literacy during pregnancy, with significant associations reported between low nutrition literacy and Spanish-speaking individuals with low household incomes and those who lack health insurance. Their study was nested within the phase III randomized clinical trial known as the Assessment of Docosahexaenoic Acid on reducing Early Preterm Birth (ADORE) study.

A similar study conducted by Camargo et al. (that was also part of the ADORE study) investigated nutrition literacy and how it relates to diet quality and acculturation among 99 pregnant Latina(x) individuals in the United States [15]. The authors also used the NLit tool and reported that 76.8 % of participants had low nutrition literacy and none of the participants in their study had high nutrition literacy. They found an association between improved diet quality and women who were 35 years or older. They also reported lower diet quality scores among women who were bicultural and were born in Latin American countries other than Mexico.

Nguyen et al. analyzed nutrition literacy levels in 360 Vietnamese pregnant women and the factors that can influence nutrition literacy levels [14]. Researchers in this study employed the Nutrition Literacy Assessment Instrument for Pregnant Women (NLAI-P) to evaluate metrics including knowledge regarding food sources, balanced nutrition, weight management, and nutrition label reading. Overall, the team found that 70.3 % of the women had inadequate nutrition literacy. Demographics like high age, normal pre-pregnancy weight, household monthly income were statistically associated with higher nutrition literacy scores. This study highlighted important financial considerations when it comes to addressing nutritional education in pregnant women.

The last study included in our review, Li et al., is unique in that it includes results from nutrition literacy evaluations in pregnant women both before and after an education intervention was introduced [13]. 88 Chinese women were randomized into 2 groups, the control group and the Comprehensive Dietary Intervention Program (CDIP) group. Total nutritional literacy score was calculated for each group before any intervention and calculated again for the CDIP group after intervention. The NLAI-P was used to measure participants’ nutritional literacy score. Ultimately, study results showed that the CDIP intervention compared to the control group was associated with a statistically significant increase in nutritional literacy (23.4 %) in pregnant women who were tested pre-to post-intervention (from 43.28 ± 7.25 to 53.39 ± 6.60, p<0.001).

The studies included in our review had many strengths. Each research study included a well-defined set of inclusion and exclusion criteria that helped define their populations of interest. These articles also utilized standardized tools to measure subject nutrition literacy levels. By using validated nutrition literacy instruments, researchers were able to quantify subject knowledge level and generate data needed for statistical analysis. Furthermore, each study employed appropriate statistical tests to analyze the data generated. Using the same standardized statistical methods and a p-value of 0.05, all these studies allow other researchers to draw comparisons between different study findings. An important nuance to consider is that each study included in this review looked at very different study populations across the world. While this can be beneficial when compiling research on a specific topic, it can make it more difficult to apply the findings to a specific population.

After summarizing these studies, we conducted a quality assessment using the Joanna Briggs Institute (JBI) Checklist for Analytical Cross-Sectional Studies [16]. This assessment helped evaluate the methodological rigor of the studies, focusing on aspects such as inclusion criteria, study design, and statistical analysis. The findings from this assessment indicate that all five studies clearly identified their inclusion criteria, used validated tools for measurement, and used appropriate statistical analysis. (See Table 2).

Due to the lack of studies that met our inclusion criteria, a meta-analysis was not feasible. Therefore, we conducted a narrative synthesis to summarize the findings thematically. We reviewed research on nutrition knowledge, attitudes, and practices (KAP) among pregnant women, along with studies involving nutrition education interventions during pregnancy. This approach helped to provide insights into the factors that impact nutrition behaviors and to identify possible interventions to support maternal and fetal health outcomes through improved nutrition literacy. We also felt it was important to focus on exploring the definitions and measures of nutrition literacy. Because there are different instruments used to evaluate nutrition literacy, clarifying how nutrition literacy is conceptualized and assessed may also highlight areas for future research in this area.

Discussion

Nutrition literacy during pregnancy is significant for all women, regardless of background or location. This was especially evident when viewing the articles included in this study as a whole, as they included women in the United States Czech Republic, China, and Vietnam. Looking at research that focused on nutrition KAP and nutrition education interventions during pregnancy, this trend continued, as there were studies published on this topic from countries all over the world. This underscores the important role that nutrition literacy plays in the health and well-being of pregnant women worldwide. And while cultural differences exist, it is possible and perhaps very likely that findings from a study in 1 country would potentially be applicable to other countries.

The studies included in this review were all cross-sectional studies; however, their assessment methods varied. As mentioned previously, 2 studies utilized the previously developed and validated NLit instrument, 2 studies used the NLAI-P, and study utilized the newly-created NKT instrument. Camargo et al. nested their studies within a clinical trial, Li et al. included their assessment in an intervention, Papežová et al. and Nguyen et al. used questionnaires for direct assessment [10], [12], [13], [14], [15]. These different strategies suggest there are multiple ways to evaluate nutrition literacy among pregnant women. At this point in time, a standardized nutrition literacy tool for use among different populations does not exist. Comparability among different populations could be enhanced if such a tool were created; however, given the diverse nature of participants that span the globe it may be impossible to develop something that could be uniformly applicable to all cultures.

Limitations

The studies included in our review had several limitations that impact the strength and generalizability of the findings. Several studies had smaller sample sizes, reducing statistical power. There was variability in the instruments used to assess nutrition literacy which limits comparability. Additionally, most of the studies were limited to specific geographic regions, which may impact broader generalizability of the findings. These limitations suggest a need for more rigorous research in this area.

Because nutrition literacy is complex, discussions continue about how to best to measure it [55]. In reaction multiple tools have been developed throughout the world for evaluating nutrition literacy, and in this review, the prior use of different instruments made it more difficult to compare the researchers’ findings. The development of a standardized instrument to measure nutrition literacy in different populations across the globe could add value to the current body of knowledge on this topic.

The fact that only 5 studies met the inclusion criteria indicates there is a severe gap in research on nutrition literacy in pregnancy. While these studies certainly enhance the general understanding of this topic, they also highlight the fact that many factors impact nutrition literacy. The overall concept of nutrition literacy is not just limited to an individual’s knowledge levels, it also involves making informed decisions every day to navigate one’s food environment. In order to fully evaluate the impact of nutrition literacy on maternal and fetal outcomes, more research is needed. Future studies targeting specific populations and socioeconomic disparities may help improve our knowledge of this topic.

Conclusions

This systematic review highlights the complexities associated with nutrition literacy among pregnant women. While the literature search revealed a limited number of relevant studies on this specific topic, the examination of related KAP and intervention studies did provide valuable insights.

As nutrition literacy encompasses more than just knowledge, there are many obstacles that pregnant women face when trying to eat healthfully. Our review highlighted challenges pregnant women face related to understanding and applying reliable nutrition information. All of the identified studies (n=5) addressed nutrition literacy through questions related to nutrition knowledge and consumer skills. But the revelation that there are only a handful of quality, relevant studies in this area also clarified that data about and insights into nutrition literacy during pregnancy is limited, and more high-quality research is needed.

Our research indicates that improvements in the social determinants of health are necessary to improve nutrition literacy in pregnant women. In addition to policy changes that may help improve social determinants of health, it may also be worthwhile to focus efforts on improving access to nutrition education during pregnancy.