Vegetarian diets during pregnancy, and maternal and neonatal outcomes

Gaps in the usage and reporting of multiple imputation for incomplete data: findings from a scoping review of observational studies addressing causal questions

BACKGROUND

Missing data are common in observational studies and often occur in several of the variables required when estimating a causal effect, i.e. the exposure, outcome and/or variables used to control for confounding. Analyses involving multiple incomplete variables are not as straightforward as analyses with a single incomplete variable. For example, in the context of multivariable missingness, the standard missing data assumptions ("missing completely at random", "missing at random" [MAR], "missing not at random") are difficult to interpret and assess. It is not clear how the complexities that arise due to multivariable missingness are being addressed in practice. The aim of this study was to review how missing data are managed and reported in observational studies that use multiple imputation (MI) for causal effect estimation, with a particular focus on missing data summaries, missing data assumptions, primary and sensitivity analyses, and MI implementation.

METHODS

We searched five top general epidemiology journals for observational studies that aimed to answer a causal research question and used MI, published between January 2019 and December 2021. Article screening and data extraction were performed systematically.

RESULTS

Of the 130 studies included in this review, 108 (83%) derived an analysis sample by excluding individuals with missing data in specific variables (e.g., outcome) and 114 (88%) had multivariable missingness within the analysis sample. Forty-four (34%) studies provided a statement about missing data assumptions, 35 of which stated the MAR assumption, but only 11/44 (25%) studies provided a justification for these assumptions. The number of imputations, MI method and MI software were generally well-reported (71%, 75% and 88% of studies, respectively), while aspects of the imputation model specification were not clear for more than half of the studies. A secondary analysis that used a different approach to handle the missing data was conducted in 69/130 (53%) studies. Of these 69 studies, 68 (99%) lacked a clear justification for the secondary analysis.

CONCLUSION

Effort is needed to clarify the rationale for and improve the reporting of MI for estimation of causal effects from observational data. We encourage greater transparency in making and reporting analytical decisions related to missing data.

Vegetarian Diets During Pregnancy: With Supplementation, Ovo-Vegetarian, Lacto-Vegetarian, Vegan, and Pescatarian Adaptations of US Department of Agriculture Food Patterns Can Be Nutritionally Adequate

BACKGROUND

The 2020-2025 Dietary Guidelines for Americans (DGA) includes a lacto-ovo vegetarian pattern (the healthy vegetarian dietary pattern [HVDP]) as a recommended dietary pattern during pregnancy.

OBJECTIVE

To adapt the HVDP for vegan, ovo-vegetarian, lacto-vegetarian, and pescatarian diets during pregnancy.

DESIGN

Using food pattern modeling, 4 adaptations of the HVDP were developed at energy levels that may be appropriate during pregnancy (1800, 2000, 2200, 2400, and 2600 kcal/day). Models were run both with and without the addition of a composite prenatal supplement.

MAIN OUTCOME MEASURES

Main outcome measures were macro- and micronutrient adequacy without exceeding recommendations for saturated fat and added sugar.

STATISTICAL ANALYSIS PERFORMED

The 2020-2025 DGA Food Pattern Modeling Report was used to define food groups and nutrients in the HVDP. The HVDP was revised to remove dairy and/or eggs or to add seafood.

RESULTS

Across all examined energy levels (1800, 2000, 2200, 2400, and 2600 kcal per day), modeled dietary patterns provided sufficient macronutrients. Without prenatal supplements, each dietary pattern met most, but not all, micronutrient recommendations. Micronutrients that were below recommendations in patterns without supplements included vitamin D, iron, vitamin E, sodium, and choline. With the addition of a composite prenatal supplement to these patterns, the nutrients below 100% of recommendations were vitamin D, choline, and sodium.

CONCLUSIONS

Overall, these results show that a HVDP and similar diets without meat, eggs, dairy, and/or seafood can provide most nutrients needed during pregnancy, albeit with some micronutrient challenges similar to those diets that include meat and other animal products.

Adherence to different forms of plant-based diets and pregnancy outcomes in the Danish National Birth Cohort: A prospective observational study

INTRODUCTION

The number of people adhering to plant-based diets has been increasing dramatically in recent years, fueled by both environmental and animal welfare concerns. Beneficial or possible adverse consequences of such diets, particularly the most restrictive forms during pregnancy, have been minimally explored. The aim of this prospective observational study was to examine associations between different forms of plant-based diets during pregnancy with birth outcomes and pregnancy complications.

MATERIAL AND METHODS

The Danish National Birth Cohort included 100 413 pregnancies to 91 381 women in 1996-2002. The population consisted of 66 738 pregnancies, about which sufficient dietary data were available and included in the study. Dietary and supplemental intake was assessed by Food Frequency Questionnaire in gestational week 25 and women were characterized as fish/poultry-vegetarians, lacto/ovo-vegetarians, vegans or omnivorous, based on their self-report in gestational week 30. Main outcome measures were pregnancy and birth complications, birthweight and small for gestational age.

RESULTS

A total of 98.7% (n = 65 872) of participants were defined as omnivorous, whereas 1.0% (n = 666), 0.3% (n = 183) and 0.03% (n = 18) identified themselves as fish/poultry vegetarians, lacto/ovo-vegetarians or vegans, respectively. Protein intake was lower among lacto/ovo-vegetarians (13.3%) and vegans (10.4%) than among omnivorous participants (15.4%). Intake of micronutrients was also considerably lower among vegans, but when dietary supplements were taken into consideration, no major differences were observed. Compared with omnivorous mothers, vegans had a higher prevalence of preeclampsia and their offspring had on average -240 g (95% confidence interval -450 to -30) lower birthweight.

CONCLUSIONS

The women reporting that they adhered to vegan diets during pregnancy had offspring with lower mean birthweight and higher risk of preeclampsia compared with omnivorous mothers. Low protein intake might be one plausible explanation for the observed association with birthweight.

Do Popular Diets Impact Fertility?

Infertility affects 15% of the population in developed countries, and its prevalence is increasing. Fertility can be influenced by different factors. Although key factors like maternal age cannot be changed, there is growing evidence that other modifiable factors, such as diet, can have an impact on fertility. Diet has become increasingly important in recent years for a number of reasons: the new trend toward a healthy lifestyle, the higher prevalence of certain digestive disorders, a lack of time that leads people to consume more prepared and processed food, and personal choice to not eat meat, among others. To meet these needs, several diets have recently become popular, such as the Mediterranean diet, known as the gold standard of health; the DASH diet, known for preventing hypertension; the Western diet, characterized by processed food; the ketogenic diet, characterized by low carbohydrate intake; and the vegetarian diet, which is the choice for people who do not eat meat or animal by-products. Diets present a unique composition characterized by the presence or absence of specific nutrients, which have also been associated with male and female fertility individually. This review assesses the impact of these diets and of macro- and micronutrients on both female and male fertility.

Association between a maternal vegetarian diet during pregnancy and the occurrence of atopic dermatitis in children

BACKGROUND

Atopic dermatitis (AD) is rising globally, with genetics and environmental factors both playing crucial roles. Dietary habits during pregnancy are linked to children's allergic disease risk. However, limited studies have explored the association between maternal vegetarian diets during pregnancy and child AD. Therefore, this study aimed to examine the relationship between maternal vegetarian diets during pregnancy and the occurrence of AD in children.

METHODS

In this study, the Taiwan Birth Cohort Study (TBCS) database was used, comprising a representative national birth cohort of infants born in Taiwan in 2005. Of 24,200 mother-child pairs in the database, 20,172 completed face-to-face interviews at 6 and 18 months. Employing a 1:10 matching strategy based on maternal age, education level, and child sex, 408 mothers who followed a vegetarian diet during pregnancy were matched with 4080 nonvegetarian mothers. This resulted in a final dataset of 4488 subjects. Logistic regression was used to explore the association between maternal vegetarian diets during pregnancy and the occurrence of AD in children.

RESULTS

Among the TBCS participants, there were 292 (1.8%) mothers who adhered to lacto-ovo vegetarianism and 116 (0.7%) mothers who adhered to veganism, totaling 408 (2.4%) vegetarians during pregnancy. Compared to children of nonvegetarian mothers, children of mothers who followed a vegetarian diet during pregnancy showed a lower risk of developing AD before 18 months of age (OR = 0.65, 95% CI = 0.45-0.93, p = 0.018).

CONCLUSION

This study suggests that a vegetarian diet during pregnancy may lower the risk of AD in children. It is essential to carry out long-term follow-up to fully understand the impact of a mother's diet on allergic conditions.

The mediating role of pregnancy-induced hypertension on pre-pregnancy body mass index and adverse neonatal outcomes in women with assisted reproductive technology

OBJECTIVE

To explore whether pregnancy-induced hypertension (PIH) mediates the association between pre-pregnancy body mass index (BMI) and adverse neonatal outcomes in women undergoing assisted reproductive technology (ART) for singleton pregnancies.

METHODS

This cohort study collected 79437 maternal data from the National Vital Statistics System (NVSS) between 2020 and 2021. Univariable and multivariable logistic regression models were applied to estimate the association between pre-pregnancy BMI and PIH in women receiving ART as well as the associations between pre-pregnancy BMI and PIH and adverse neonatal outcomes. The mediation effect of PIH on the association between pre-pregnancy BMI and adverse neonatal outcomes was estimated according to the total effect, natural direct effect, natural indirect effect, and percentage of mediation.

RESULTS

There were 25769 participants had adverse neonatal outcomes at the end of the follow-up. After adjusting for confounding factors, an increased risk of PIH in women receiving ART was identified in those with pre-pregnancy BMI ≥25 kg/m2 [odds ratio (OR)=1.92, 95% confidence interval (CI):1.84-2.01]. Pre-pregnancy BMI ≥25 kg/m2 was associated with an increased risk of adverse neonatal outcomes (OR = 1.26, 95%CI:1.22-1.30). Women with PIH had an increased risk of adverse neonatal outcomes (OR = 1.79, 95%CI:1.71-1.87). The percentage mediated by PIH in the association between pre-pregnancy BMI and adverse neonatal outcomes was 21.30%.

CONCLUSION

PIH partially mediated the association between pre-pregnancy BMI and adverse neonatal outcomes in women receiving ART, which recommends that women control weight before receiving ART.

The Impact of Maternal Plant-Based Diet on Obstetric and Neonatal Outcomes-A Cross-Sectional Study

BACKGROUND

In the last decades, plant-based diets have gained popularity. Pregnancy is not a contraindication to follow a meat-free diet. This study aimed to compare maternal and neonatal outcomes between women who followed a plant-based diet with those on an omnivore diet. Our second purpose was to investigate the association between physical activity level in combination with diet type and the occurrence of GDM and gestational hypertension.

METHODS

A questionnaire was distributed electronically via social media. The survey was conducted on a population of Polish women.

RESULTS

The final research group included 1015 women. The results showed that a maternal plant-based diet 6 months before pregnancy and during pregnancy does not change the incidence of GDM, anemia, and gestational hypertension. Moreover, no association was found between a diet type before conception and a delivery method or newborn birth weight. Among women who followed an omnivore diet, the risk of GDM was lower in a group with adequate physical activity during 6 months before conception (p = 0.0166). However, the combination of a plant-based diet with adequate activity during the preconception period did not influence GDM incidence.

CONCLUSIONS

Our study indicates that a plant-based diet during the preconception period is not worse than an omnivore diet.

Vegetarian diets and diets which restrict animal-source foods during childhood in high-income countries

Increasing numbers of populations in the West are restricting their intake of meat and other animal products for reasons relating to health or ethics; in many countries, these restrictions are already common for cultural, religious, or socio-economic reasons. By following their parent's diet, children are exposed in parallel. This narrative review aims at assessing current data regarding vegetarian diets in children from birth to 18 years of age, which include, by increasing degree of restriction, flexitarian, lacto-ovo-vegetarian, lacto-vegetarian, pescatarian, vegan and macrobiotic diets. The 202 references include 45 studies in children. The more restrictive the diet and the younger the child, the greater the risk of nutritional deficiency. Of particular concern are vitamin B12, iron, zinc, calcium, n-3 long-chain polyunsaturated fatty acids, and protein and energy intake, especially in pregnant and nursing women, infants and young children. Providing an adequate lacto-ovo-vegetarian diet is relatively easy, whereas the maintenance of more restrictive diets may be challenging. The benefits and risks of vegetarian diets in adults are relatively well documented, but data for children are scarce. Vegan and macrobiotic diets should be discouraged in pregnant and lactating mothers as well as in young children, who, otherwise, should pay careful attention to ensuring nutritional adequacy, blood testing and appropriate supplementation. The health consequences of a chosen diet should be discussed with parents and adolescents to ensure the best possible adherence to advice and prescriptions. There is a need for well conducted studies in children but also for better knowledge of nutrition in healthcare professionals.Abbreviations: ALA: α-linolenic acid; ARA: arachidonic acid; ASF: animal source foods; BMC: bone mineral content; BMD: bone mineral density; DHA: docosahexaenoic acid; DRV: dietary reference value; EPA: eicosapentaenoic acid; FLD: flexitarian diet; LA: linoleic acid; LC-PUFA: long-chain polyunsaturated fatty acids; LOVD: lacto-ovo-vegetarian diet; LVD: lacto-vegetarian diet; MAD: macrobiotic diet; OMD: omnivorous diet; PSF: plant-source foods; SFA: saturated fatty acids; VGD: vegetarian diets; VND: vegan diet.

The effects of plant-based dietary patterns on the risk of developing gestational diabetes mellitus: A systematic review and meta-analysis

BACKGROUND

The worldwide prevention of gestational diabetes mellitus (GDM) is a significant health challenge. Plant-based dietary patterns are a series dietary habits that emphasized foods derived from plant sources more and from animal foods less. Now, no consensus exists on the effects of plant-based dietary patterns on the incident of GDM.

OBJECTIVE

This study aimed to estimate the effects of plant-based dietary patterns on the risk of developing GDM.

METHODS

This systematic review was conducted following the checklist of PRISMA. Six electronic databases including PubMed, Embase, Web of Science, China National Knowledge Infrastructure, Wangfang, and Chinese Scientific Journals Database were searched from inception to November 20, 2022. A fixed or random effect model was used to synthesize results of included studies. Then, subgroup analysis, meta-regression and sensitivity analysis were performed to assure the reliability and stability of the results.

RESULTS

Ten studies including 32,006 participants were identified. The results of this study showed that the better adherence to the plant-based dietary patterns was related to the lower risk of developing GDM (RR = 0.88[0.81 to 0.96], I2 = 14.8%). The slightly stronger association between plant-based diets and the risk of developing GDM was found when healthy plant-based dietary pattern index was included in pooled estimate (RR = 0.86[0.79 to 0.94], I2 = 8.3%), compared with that unhealthy one was included (RR = 0.90[0.82 to 0.98], I2 = 8.3%).

CONCLUSION

The plant-based dietary patterns are associated with a lower risk of developing GDM. Furthermore, healthy plant-based dietary patterns are more recommended than unhealthy one. It is significant to help medical staff to guide pregnant women to choose reasonable diets.

Knowledge domain and research trends for Gestational Diabetes Mellitus and nutrition from 2011 to 2021: a bibliometric analysis

Objective

Nutrient management and lifestyle changes are the frontlines of treatment for all pregnant women diagnosed with Gestational Diabetes Mellitus (GDM). This study aimed to identify the global research architecture, trends, and hotpots of GDM and nutrition.

Methods

We obtained publications from the sub-databases of Science Citation Index Expanded and Social Science Citation Index sourced from the Web of Science Core Collection database on January 4, 2022, using publication years between 2011 and 2021. CiteSpace software, VOSviewer, and Microsoft Excel 2019 were used to conduct the bibliometric analyses.

Results

A growing publication trend was observed for GDM and nutrition, and this field has great potential. More GDM and nutrition research has been conducted in developed countries than developing countries. The top three authors with a high publication frequency, co-citations, and a good h-index were from the United States. There were the four studies of randomized controlled trials (RCTs) or meta-analyses of RCTs, as well as one review in the top five items of cited literature. Keywords were categorized into four clusters based on the keywords visualization.

Conclusion

It is important to strengthen the collaboration between nations of different economies to produce more high-quality research on GDM and nutrition. It may be beneficial to further study the etiology, diagnosis, and treatment of GDM based on current results to provide a new perspective on GDM and nutrition.

Prepregnancy plant-based diets and the risk of gestational diabetes mellitus: a prospective cohort study of 14,926 women

BACKGROUND

Emerging evidence suggests beneficial impacts of plant-based diets on glucose metabolism among generally healthy individuals. Whether adherence to these diets is related to risk of gestational diabetes mellitus (GDM) is unknown.

OBJECTIVES

We aimed to examine associations between plant-based diets and GDM in a large prospective study.

METHODS

We included 14,926 women from the Nurses' Health Study II (1991-2001), who reported ≥1 singleton pregnancy and without previous GDM before the index pregnancy. Prepregnancy adherence to plant-based diets was measured by an overall plant-based diet index (PDI), healthful plant-based diet index (hPDI), and unhealthful plant-based diet index (uPDI) as assessed by FFQs every 4 y. Incident first-time GDM was ascertained from a self-reported physician diagnosis, which was previously validated by review of medical records. We used log-binomial models with generalized estimating equations to calculate RRs and 95% CIs for associations of PDIs with GDM.

RESULTS

We documented 846 incident GDM cases over the 10-y follow-up among 20,707 pregnancies. Greater adherence to the PDI and hPDI was associated with lower GDM risk. For the PDI, the multivariable-adjusted RR (95% CI) comparing the highest and lowest quintiles (Q5 compared with Q1) was 0.70 (0.56, 0.87) (Ptrend = 0.0004), and for each 10-point increment was 0.80 (0.71, 0.90). For the hPDI, the RR (95% CI) of Q5 compared with Q1 was 0.75 (0.59, 0.94) (Ptrend = 0.009) and for each 10-point increment was 0.86 (0.77, 0.95). After further adjustment for prepregnancy BMI, the associations were attenuated but remained significant: for the PDI, the RR (95% CI) for each 10-point increment was 0.89 (0.79, 1.00) and the corresponding RR (95% CI) was 0.89 (0.80, 0.99) for the hPDI. The uPDI was not associated with GDM.

CONCLUSIONS

Our study suggests that greater prepregnancy adherence to a healthful plant-based diet was associated with lower risk of GDM, whereas an unhealthful plant-based diet was not related to GDM risk.

The Safe and Effective Use of Plant-Based Diets with Guidelines for Health Professionals

Plant-based diets, defined here as including both vegan and lacto-ovo-vegetarian diets, are growing in popularity throughout the Western world for various reasons, including concerns for human health and the health of the planet. Plant-based diets are more environmentally sustainable than meat-based diets and have a reduced environmental impact, including producing lower levels of greenhouse gas emissions. Dietary guidelines are normally formulated to enhance the health of society, reduce the risk of chronic diseases, and prevent nutritional deficiencies. We reviewed the scientific data on plant-based diets to summarize their preventative and therapeutic role in cardiovascular disease, cancer, diabetes, obesity, and osteoporosis. Consuming plant-based diets is safe and effective for all stages of the life cycle, from pregnancy and lactation, to childhood, to old age. Plant-based diets, which are high in fiber and polyphenolics, are also associated with a diverse gut microbiota, producing metabolites that have anti-inflammatory functions that may help manage disease processes. Concerns about the adequate intake of a number of nutrients, including vitamin B12, calcium, vitamin D, iron, zinc, and omega-3 fats, are discussed. The use of fortified foods and/or supplements as well as appropriate food choices are outlined for each nutrient. Finally, guidelines are suggested for health professionals working with clients consuming plant-based diets.

Organic food use, meat intake, and prevalence of gestational diabetes: KOALA birth cohort study

Purpose

To evaluate whether consumption of organic food and reduced intake of meat products in pregnancy are associated with lower prevalence of gestational diabetes (GD).

Methods

Women participating in the KOALA Birth Cohort Study with valid informed consent, a singleton pregnancy and information on their food intake were considered in this cross-sectional analysis. Participants with and without GD were compared with each other in terms of dietary characteristics (n = 37 and n = 2766, respectively). Multivariable logistic regression (LR) was used to adjust for relevant covariates.

Results

Organic food consumption tended to be lower, although not significantly, in women with GD compared to women without GD, whereas consumption of meat was positively associated with GD prevalence. LR modelling showed that GD was significantly associated with higher consumption of meat and, in addition, also of cheese, after adjustment for other relevant covariates. GD was associated with some indicators of animal product intake, namely dietary animal to plant protein ratio and maternal plasma arachidonic acid (for the latter, data available for n = 16 and n = 1304, respectively). Food patterns of participants with GD were characterised by more meat products and less vegetarian products.

Conclusions

Due to the low number of participants with GD, results have to be interpreted cautiously. Consumption of organic food during pregnancy does not seem to be markedly associated with a lower GD prevalence; lower intake of meat and cheese, irrespective of its origin (organic or conventional), does. The latter supports previous studies suggesting a causal association between consumption of animal products and GD.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02601-4.