The nutritional status during pregnancy not only affects pregnancy outcomes, but is also closely related to maternal health, fetal physical and intellectual development, and the health of offspring in adulthood (1). By improving dietary structures and implementing scientific nutritional interventions such as nutrient fortified foods and supplements, it is possible to effectively mitigate health issues associated with inadequate, excessive, or imbalanced intake of food, energy and nutrients, thereby providing more comprehensive health protection for both mothers and children (2, 3).

The dietary survey is a pivotal tool in comprehensively assessing the dietary structures, as well as the quantity and quality of energy and nutrients intake among pregnant women over a specific period. Accurate collection of dietary intake data is essential for informing health and nutrition policies. Retrospective dietary survey methods, such as 24-h recall and food frequency method, are the most widely used methods for collecting dietary information, depending on respondents’ ability to recall and describe their food consumption before the survey (4). The accuracy of dietary data tends to decline as the time interval extends between the meal intake and the subsequent dietary recall, with errors becoming increasingly pronounced over time (5). Additionally, these retrospective methods are often based on respondents’ self-assessment of their food consumption, demanding a certain level of educational proficiency and practical life experience to ensure the accuracy and reliability of the data provided (6). However, in the general population’s mindset, there is often a disconnect between the visual perception of various foods and their actual weight, making precise estimation of food weight a significant hurdle in dietary data collection.

So far, the application of specialized dietary survey methods to study the dietary nutritional status of Chinese pregnant women have mainly focused on specific groups such as rural areas and ethnic minorities, or have been limited to certain local areas such as western areas and eastern coastal cities, or have only focused on single nutrients such as iodine or iron (7–9). The dietary status during pregnancy exhibited considerable variation across different Chinese geographic locations, socioeconomic strata, and diverse dietary cultures. For instance, in Urumqi, Xinjiang Uygur Autonomous Region, the consumption of staple foods, vegetables, milk and its products, as well as fish, shrimp, and shellfish among pregnant women were inadequate (10). Conversely, in Suzhou, Jiangsu Province, there were over-consumption of staple foods and fruits, while the consumption of milk and its products was not adequate (11). Therefore, it is necessary to carry out dietary surveys in multiple geographic regions and among different socioeconomic groups simultaneously to obtain more reliable and nationally representative data.

Currently, the only nationwide dietary survey is the China Health and Nutrition Survey (CHNS) (12), but unfortunately, it does not take into account the consumption of nutritional supplements. In China, various domestic or imported nutritional supplements have been introduced to the market, which are commonly used to improve the nutritional intake of individuals with nutrient deficiencies. A previous survey conducted in three Asian-Pacific countries revealed a concerning phenomenon: in China, 46.0, 42.0, and 39.0% of pregnant women (with a sample size of 600) took multiple vitamins during the first, second, and third trimesters of pregnancy, respectively (13). This highlights the necessity of considering the potential impact of nutritional supplements on the nutritional status of pregnant women.

To overcome these limitations, using an online dietary diary method featuring a food atlas embedded with three visual reference systems (6), this study collected baseline data on diet and nutritional supplements through a multi-regional cross-sectional survey to assess the dietary structures, energy, and nutrient intake of Chinese pregnant women during the second and third trimesters, to identify risks of deficiencies, excesses, or imbalances in energy and nutrients. In addition, with the acceleration of China’s urbanization process and significant improvement in living standards, rural residents are struggling to cope with ongoing challenges, including low income levels, limited education levels, traditional ways of thinking, and inadequate transportation infrastructure, all of which will have an impact on their food supply capacity and dietary behavior. Therefore, this study further compared the differences between urban and rural areas, which will help provide appropriate dietary guidance and recommendations for pregnant women in different regions.

Herein, utilizing a specialized dietary survey method, we conducted a nationwide survey in China to comprehensively compare the dietary structures and the intake of energy and nutrients from both diets and nutritional supplements among pregnant women during their second and third trimesters, with a focus on the differences between urban and rural areas. Our study surpasses previous studies in two major aspects: a nationally representative and equitably distributed sample of pregnant women, ensuring representation of the Chinese pregnant population; and a specialized dietary survey method that significantly improves the accuracy of dietary intake estimation. Our findings can provide a scientific foundation for dietary guidance and interventions for Chinese pregnant women.

In this study, we found that pregnant women during the second and third trimesters suffered from inadequate energy intake, the proportion of urban and rural pregnant women with energy intake below the EER value exceeded 70.0%. In contrast, a study involving 793 pregnant women in Spain showed that 82.6% of pregnant women had adequate energy intake in the third trimester (15). This phenomenon may be attributed to the difference in evaluation standards between different countries, as well as underestimation of cooking oil consumption and neglect of additional meals due to the complexity of Chinese cuisine. These are common challenges encountered in Chinese dietary surveys. Moreover, this group also had inadequate protein intake, especially noticeable during the third trimester of pregnancy. Analysis of food categories revealed that the inadequate consumption of fish, shrimp and shellfish, milk and its products, and soybean and its products were key contributors. In terms of energy ratios, this study revealed that over 70.0% of pregnant women derived less than 50.0% of their energy from carbohydrates, while more than 80.0% obtained over 30.0% of energy from fats. These findings aligned with a study of 1,652 individuals in Chengdu City, where the proportion of pregnant women with energy intake from fat exceeding 30.0% in the second and third trimesters was 77.6 and 82.9%, respectively (20). By analyzing the consumption of foods from different categories in this study, the reason for the above phenomenon is that this group has inadequate consumption of potatoes and vegetables, and excessive consumption of livestock meat and poultry and cooking oil. This dietary imbalance is not only a matter of personal choice, but also closely related to socioeconomic determinants. For instance, the intake of high-quality protein sources (such as fish and dairy products) and diverse vegetables in rural areas was significantly lower than that in urban areas, which may be related to food affordability, availability in local markets, and the dietary knowledge popularization. Based on these findings, it is recommended that urban and rural pregnant women in the second and third trimesters of pregnancy in China increase their consumption of potatoes, vegetables, fish, shrimp and shellfish, milk and its products, as well as soybeans and its products, while reducing their consumption of livestock meat and poultry and cooking oil to ensure a balanced dietary structure during pregnancy.

In this study, after investigating diets and nutritional supplements, the inadequate intake of vitamin A and B vitamins was observed among both urban and rural pregnant women. Notably, the nutritional status of rural pregnant women in the third trimester was particularly concerning. According to the 2015 CHNS data, although there was a significant improvement in the vitamin A nutritional status among rural pregnant women in China, attention should still be paid to the third trimester, with a deficiency rate of 2.1% and a marginal deficiency rate of 14.2% (21). Our result was consistent with this, finding that the proportion of rural pregnant women in the third trimester with inadequate vitamin A intake was 82.4%. The main sources of vitamin A are animal liver and dark-green leafy vegetables and fruits (19). If these foods were not consumed during the survey period, there would be a substantial variation in vitamin A intake among pregnant women. Therefore, it is recommended that pregnant women’s diets include animal liver 1 ~ 2 times per week to increase vitamin A intake (16). In our study, the intakes of B vitamins (excluding vitamin B₃ and vitamin B₁₂) were generally not ideal among pregnant women, especially in rural areas. In daily diet, vitamin B₁ mainly comes from cereal and its products, but as the refinement level of cereal processing increases, the content of vitamin B₁ gradually decreases (19). In our study, the consumption of cereal and its products among pregnant women remained normal, so the inadequate intake of vitamin B₁ may be related to the overly refined processing of cereal and its products in this population. As for vitamin B₉, its main sources are animal liver and green vegetables (19). More than 95.0% of pregnant women in this survey have inadequate intake of vitamin B₉, which may be partly due to their inadequate intake of these foods. Due to the easy degradation of vitamin B₉ during food storage or cooking, it is difficult to meet the needs of pregnant women solely relying on food sources (16). Therefore, taking additional supplements is particularly crucial on top on a balanced diet. In China, more attention has been paid to taking vitamin B₉ supplements before and during the first trimester of pregnancy to prevent neural tube defects. A cross-sectional study in Shanghai showed that 93.4% (14585/15615) of pregnant women in the first trimester took vitamin B₉ supplements (22). However, recent studies, including in China, advocate for the continued supplementation of vitamin B₉ or multivitamins containing vitamin B₉ by pregnant women during the second and third trimesters for the well-being of pregnant women and their fetuses (23, 24). Lack of vitamin B₉ in the second and third trimesters of pregnancy may lead to megaloblastic anemia, increase the risk of gestational hypertension, and be associated with placental abruption, fetal growth restriction, premature birth, etc. (25). These are still common pregnancy complications and adverse pregnancy outcomes among Chinese pregnant women. Therefore, further guidance is needed for pregnant women to supplement vitamin B₉ in the second and third trimesters, whether in rural or urban areas of China. In addition, the urban–rural differences in intake of vitamin A and B vitamins highlight the impact of education level and medical accessibility. Public health measures need to be precisely designed to address these socioeconomic barriers.

In terms of mineral intake, our study found that pregnant women in the second and third trimesters experienced inadequate intake of calcium, magnesium, and iodine, with this issue being particularly severe in rural areas. Inadequate calcium intake during pregnancy may lead to maternal complications, such as muscle cramps and gestational hypertension, and may have adverse effects on fetal growth, development and bone formation (16, 26, 27), which is a key concern for Chinese pregnant women and newborns. Our study found that the daily calcium intake of pregnant women during the second and third trimesters decreased, with more than 78.0% of rural pregnant women having calcium intakes below the EAR. In contrast, a survey conducted in the United States among 1,100 pregnant women found that less than 20.0% of participants had calcium intake from diet and nutritional supplements below the EAR, primarily due to the widespread habit of consuming milk and its products among American pregnant women (28). Given that milk and its products are the best source of dietary calcium, promoting its consumption among Chinese pregnant women remains a critical step in addressing this issue (16). Previous dietary surveys of pregnant women in Spain, Japan, and certain regions of China have rarely focused on magnesium intake (10, 11, 15, 29). In our study, however, it also emerged as a concern, with more than 70.0% of rural pregnant women having its intake below the EAR during the second and third trimesters. Similar findings were reported in the United States, where 34.1 ~ 41.7% of pregnant women had dietary magnesium intake below the EAR, a figure that only modestly improved to 24.4 ~ 34.6% with nutritional supplementation (28). This suggests that supplements cannot bridge the magnesium gap in dietary intake. Magnesium, a cofactor for enzymes involved in energy metabolism, protein synthesis, and DNA and RNA synthesis, is an essential mineral for maintaining maternal health and fetal growth and development (30). To ensure its adequate intake, pregnant women are encouraged to consume magnesium-rich foods such as whole grains, legumes, and nuts (19). Iodine, another essential mineral, plays a critical role in thyroid hormone synthesis (19). Its deficiency in pregnant women not only compromises maternal health but can also impair the intellectual and physical development of the fetus (19). A study of 4,635 pregnant women in Shanghai showed that 54.5% of pregnant women had iodine deficiency (31). While China’s iodized salt policy has been fundamental in reducing iodine deficiency disorders, our study found that 58.5 ~ 71.2% of pregnant women in their second and third trimesters still had inadequate iodine intake, with rural areas facing greater challenges. Given the elevated iodine requirements during pregnancy, relying solely on iodized salt is inadequate. Supplementing through iodine-rich foods, particularly seafood, is essential to meet the increased nutritional demands of this critical physiological stage. Moreover, the persistent inadequacy of key minerals like calcium and iodine, particularly in rural areas, points to systemic issues beyond individual diet choices. These include the economic accessibility of nutrient-dense foods like dairy and seafood, and potentially the variable implementation of food fortification programs. To address these issues, it is necessary to promote nutrition intervention measures at the level of public health policies, strengthen nutrition education in rural areas, and improve the implementation mechanism of food reinforcement projects.

Based on this nationwide survey, we propose multi-level strategies to improve maternal nutrition in China. At the individual level, culturally appropriate health education should be provided, focusing on balanced diets and proper nutrient supplementation, especially for rural pregnant women. At the health service level, antenatal care should include structured dietary assessment, personalized counseling, and locally adapted nutrition education. Healthcare provider training is essential. At the policy and systems level, structural actions should address socioeconomic drivers of dietary inequity. These include enhancing food fortification and targeted supplement distribution in underserved areas, implementing economic measures such as subsidies to improve access to nutritious foods for low-income families, and updating national dietary guidelines and strengthening long-term nutritional monitoring systems.

However, this study has some limitations. Firstly, our study is limited to pregnant women in their second and third trimesters. Women typically confirm their pregnancy 6 ~ 7 weeks after a missed menstrual period. Subsequently, they often experience early pregnancy symptoms such as nausea, vomiting, and reduced appetite. These factors not only make recruiting participants in the first trimester highly challenging but also compromise dietary intake accuracy during this period. Secondly, although a quantitative food atlas was used to improve the accuracy of food weight estimation, the inherent complexity of dietary surveys, communal dining habits, and the intricate diversity of Chinese cuisine, may introduce unavoidable biases into the data reported. Thirdly, the analysis focused on group differences without conducting multivariate adjustment for confounding factors such as income, education level, or parity, which may explain part of the urban–rural gap. Finally, the cross-sectional design precluded causal inference and failed to capture seasonal or trimester-specific dietary variations, thereby limiting longitudinal insight into how maternal diet and nutrient intake affects maternal and infant health outcomes.

In summary, this nationwide survey provides a comprehensive comparison of dietary structures and nutrient intake among pregnant women in their second and third trimesters in China, highlighting significant gaps in energy, protein, vitamins and minerals between urban and rural areas. Future research should adopt longitudinal designs to establish causality and explore how socioeconomic factors mediate the impact of nutrition on health outcomes. By integrating these individual, service, and policy-level strategies, a synergistic approach can be forged to effectively bridge the urban–rural nutritional gap and improve maternal and infant health nationwide.