Vitamin D supplementation for women during pregnancy

ABSTRACT BACKGROUND: Vitamin D deficiency or insufficiency is thought to be common among pregnant women. Vitamin D supplementation during pregnancy has been suggested as an intervention to protect against adverse pregnancy outcomes. OBJECTIVES: To examine whether oral supplements with vitamin D alone or in combination with calcium or other vitamins and minerals given to women during pregnancy can safely improve maternal and neonatal outcomes. METHODS: Search methods: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (23 February 2015), the International Clinical Trials Registry Platform (31 January 2015), the Networked Digital Library of Theses and Dissertations (28 January 2015) and also contacted relevant organisations (31 January 2015). Selection criteria: Randomized and quasi-randomized trials with randomization at either individual or cluster level, evaluating the effect of supplementation with vitamin D alone or in combination with other micronutrients for women during pregnancy. Data collection and analysis: Two review authors independently i) assessed the eligibility of studies against the inclusion criteria ii) extracted data from included studies, and iii) assessed the risk of bias of the included studies. Data were checked for accuracy. The quality of the evidence was assessed using the GRADE approach. MAIN RESULTS: In this updated review we included 15 trials assessing a total of 2833 women, excluded 27 trials, and 23 trials are still ongoing or unpublished. Nine trials compared the effects of vitamin D alone versus no supplementation or a placebo and six trials compared the effects of vitamin D and calcium with no supplementation. Risk of bias in the majority of trials was unclear and many studies were at high risk of bias for blinding and attrition rates. Vitamin D alone versus no supplementation or a placebo Data from seven trials involving 868 women consistently show that women who received vitamin D supplements alone, particularly on a daily basis, had higher 25-hydroxyvitamin D than those receiving no intervention or placebo, but this response was highly heterogeneous. Also, data from two trials involving 219 women suggest that women who received vitamin D supplements may have a lower risk of pre-eclampsia than those receiving no intervention or placebo (8.9% versus 15.5%; risk ratio (RR) 0.52; 95% CI 0.25 to 1.05, low quality). Data from two trials involving 219 women suggest a similar risk of gestational diabetes among those taking vitamin D supplements or no intervention/placebo (RR 0.43; 95% CI 0.05, 3.45, very low quality). There were no clear differences in adverse effects, with only one reported case of nephritic syndrome in the control group in one study (RR 0.17; 95% CI 0.01 to 4.06; one trial, 135 women, low quality). Given the scarcity of data for this outcome, no firm conclusions can be drawn. No other adverse effects were reported in any of the other studies. With respect to infant outcomes, data from three trials involving 477 women suggest that vitamin D supplementation during pregnancy reduces the risk preterm birth compared to no intervention or placebo (8.9% versus 15.5%; RR 0.36; 95% CI 0.14 to 0.93, moderate quality). Data from three trials involving 493 women also suggest that women who receive vitamin D supplements during pregnancy less frequently had a baby with a birthweight below 2500 g than those receiving no intervention or placebo (RR 0.40; 95% CI 0.24 to 0.67, moderate quality). In terms of other outcomes, there were no clear differences in caesarean section (RR 0.95; 95% CI 0.69 to 1.31; two trials; 312 women); stillbirths (RR 0.35 95% CI 0.06, 1.99; three trials, 540 women); or neonatal deaths (RR 0.27; 95% CI 0.04, 1.67; two trials, 282 women). There was some indication that vitamin D supplementation increases infant length (mean difference (MD) 0.70, 95% CI -0.02 to 1.43; four trials, 638 infants) and head circumference at birth (MD 0.43, 95% CI 0.03 to 0.83; four trials, 638 women). Vitamin D and calcium versus no supplementation or a placebo Women who received vitamin D with calcium had a lower risk of pre-eclampsia than those not receiving any intervention (RR 0.51; 95% CI 0.32 to 0.80; three trials; 1114 women, moderate quality), but also an increased risk of preterm birth (RR 1.57; 95% CI 1.02 to 2.43, three studies, 798 women, moderate quality). Maternal vitamin D concentration at term, gestational diabetes, adverse effects and low birthweight were not reported in any trial or reported only by one study. AUTHORS CONCLUSIONS: New studies have provided more evidence on the effects of supplementing pregnant women with vitamin D alone or with calcium on pregnancy outcomes. Supplementing pregnant women with vitamin D in a single or continued dose increases serum 25-hydroxyvitamin D at term and may reduce the risk of pre-eclampsia, low birthweight and preterm birth. However, when vitamin D and calcium are combined, the risk of preterm birth is increased. The clinical significance of the increased serum 25-hydroxyvitamin D concentrations is still unclear. In light of this, these results need to be interpreted with caution. Data on adverse effects were lacking in all studies. The evidence on whether vitamin D supplementation should be given as a part of routine antenatal care to all women to improve maternal and infant outcomes remains unclear. While there is some indication that vitamin D supplementation could reduce the risk of pre-eclampsia and increase length and head circumference at birth, further rigorous randomized trials are required to confirm these effects.

Consideraciones sobre la elaboración de las directrices de nutrición de la Organización Mundial de la Salud y su implementación / Considerations on the development of nutrition-related guidelines by the World Health Organization and their implementation

La Organización Mundial de la Salud (OMS) sigue un proceso complejo y riguroso para la elaboración de directrices mundiales. En el caso de las directrices relacionadas con nutrición, la participación conjunta de las autoridades de los Estados Miembros de la OMS y sus aliados, incluidos aquellos de la economía social y solidaria, es clave para fortalecer el proceso de elaboración de directrices informadas por las pruebas científicas y su posterior implementación, como parte de las estrategias nacionales de salud pública. Para las autoridades en materia de salud y desarrollo social, la OMS desarrolla una serie de herramientas para la formulación de políticas informadas por las pruebas científicas, considerando su pertinencia, relevancia e implementabilidad. Este proceso de adopción y adaptación debe considerar aspectos de equidad, para evitar la ampliación de brechas en salud. Las directrices mundiales de la OMS contribuyen a que las intervenciones en nutrición en sus Estados Miembros sean implementadas de manera adecuada. Dos experiencias de implementación de intervenciones en nutrición, una en Panamá y otra en Perú, ejemplifican este proceso. El artículo concluye sugiriendo profundizar en el conocimiento y aplicación de la investigación de la implementación de programas para identificar los factores que permiten a una intervención ser efectiva, tener una mejor estrategia de escalabilidad y contribuir a la equidad en salud.

The World Health Organization (WHO) follows a complex and rigorous process to develop global guidelines. With regard to nutrition-related guidelines, the joint participation of national authorities from Member States and their partners, including those of the social economy, is key to strengthening the process of evidence-informed guideline development and the subsequent implementation as part of national public health strategies. WHO puts forward a series of tools that can assist national authorities on health and social development in the elaboration of evidenceinformed policies, considering their pertinence, relevance and implementability. This adoption and adaptation process must consider equity in order to avoid widening existing inequities. WHO global nutrition guidelines contribute to the effective implementation of nutrition interventions in Member States. Two experiences of implementation, one in Panama and one in Peru, exemplify this process. The paper ends by suggesting a deeper understanding and utilization of implementation research during programmes to identify what factors ensure effective interventions, appropriate scale up strategies and greater health equity.

The Micronutrient Survey Manual: A Manual for Assessing Vitamin and Mineral Nutritional Status and Interventions Using Cross-sectional Surveys.

Objectives: An important component of public health nutrition programs is the periodic assessment of vitamin and mineral nutritional status and coverage of micronutrient interventions. Performing high quality cross-sectional surveys can be enhanced by the availability of guidance on steps in survey methods, sample size, sampling methods, data collection, analysis and interpretation, dissemination of results, and appropriate feedback to improve intervention programs. A manual to assist implementers is described. Methods: A previously published manual, "Indicators and Methods for Cross-Sectional Surveys of Vitamin and Mineral Status of Populations", by the Centers for Disease Control and Prevention (CDC) and the Micronutrient Initiative (MI) served as the basis for this newer manual. New technical partners, WHO and UNICEF, have collaborated in the development of this up-to-date "Micronutrient Survey Manual". Results: In addition to updated resources for the assessment of anemia and iodine, iron, and vitamin A deficiencies, the manual has added information on folate and zinc deficiencies. Program indicators for assessing fortification of staple foods, point-of-use fortification with micronutrient powders, micronutrient supplementation, and dietary counselling are included. The manual contains detailed information on biologic sample collection and processing, sample size calculations, and analysis of survey data. Quality assurance throughout the survey process is emphasized. The issues of ethics, confidentiality, and informed consent are addressed. Conclusions: The "Micronutrient Survey Manual" can assist survey managers to improve the validity, efficiency, and standardization of cross-sectional surveys to better serve public health practice.

Effects of Daily Iron Supplementation on Physical Performance in Women of Reproductive Age: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

Objectives: Animal and human observational studies suggest iron deficiency impairs physical exercise performance but findings from randomized trials are conflicting. Iron deficiency and anaemia are especially common in women of reproductive age (WRA). We therefore performed a systematic review and meta-analysis to determine the effect of iron supplementation on exercise performance in WRA. Methods: We searched the Cochrane Central Register of Clinical Trials, MEDLINE, Scopus (comprising Embase and MEDLINE), WHO regional databases and other sources in July 2013. Randomised controlled trials that measured exercise outcomes in WRA randomized to daily oral iron supplementation versus control were eligible. Random-effects meta-analysis was used to calculate Mean Differences (MD) and Standardised MDs (SMD). Risk of bias was assessed using the Cochrane risk-of-bias tool. Results: Of 6757 titles screened, 22 eligible studies contained extractable data. Only 3 were at overall low risk of bias. Iron supplementation improved both maximal exercise performance, demonstrated by an increase in VO2 max (relative VO2 max: MD 2.35 mL/kg/min [95% CI 0.82, 3.88], P=0.003, 18 studies; absolute VO2 max: MD 0.11 L/min [0.03, 0.20], P=0.01, 9 studies; overall VO2 max: SMD 0.37 [0.11, 0.62] P=0.005, 20 studies), and submaximal exercise performance demonstrated by a lower heart rate (MD -4.05 beats per minute [-7.25, -0.85], P=0.01, 6 studies) and proportion of VO2 max (MD -2.68% [-4.94, -0.41], P=0.02, 6 studies) required to achieve defined workloads. Conclusions: Daily iron supplementation improves maximal and submaximal exercise performance in WRA, providing a rationale to prevent and treat iron deficiency in this group.

An evaluation of a global vitamin and mineral nutrition surveillance system / Evaluación de un sistema global de vigilancia nutricional sobre vitaminas y minerales

Evaluation at all levels is a fundamental function at World Health Organization (WHO). Evaluation of public health surveillance systems is essential to ensure that problems of public health importance are monitored efficiently and effectively. The WHO's Vitamin and Mineral Nutrition Information System (VMNIS) was evaluated from the perspective of public health surveillance and informatics. Steps included: engaging the stakeholders of the evaluation; describing the surveillance system; focusing the evaluation design; gathering credible evidence regarding system performance; justifying and stating conclusions and recommendations, and sharing lessons learned from the evaluation. Following this assessment, WHO has begun major efforts to upgrade and expand the VMNIS and now the database is more flexible and efficient. The database evaluation summarized in this paper provides a good example of how public health evaluation frameworks can lead to improved surveillance and enhanced information systems, thus making progress toward the ultimate goal of improving public health.

La evaluación en todos los niveles es una función fundamental en la Organización Mundial de la Salud (OMS). La evaluación de los sistemas de vigilancia epidemiológica es esencial para asegurar que los problemas de importancia para la salud pública sean monitorizados de manera eficiente y efectiva. El Sistema de Información Nutricional sobre Vitaminas y Minerales (VMNIS, por sus siglas en inglés) se evaluó desde la perspectiva de sistema de vigilancia e informática en salud pública. Los pasos incluyeron: el involucramiento de las partes interesadas en la evaluación, la descripción del sistema de vigilancia, el enfoque del diseño para la evaluación, la recopilación de pruebas fiables sobre el rendimiento del sistema, la justificación y desarrollo de conclusiones y recomendaciones, y la diseminación de las lecciones aprendidas de la evaluación. Después de este proceso, la OMS inició importantes esfuerzos para mejorar y ampliar el Sistema de Información Nutricional sobre Vitaminas y Minerales para lograr una base de datos más flexible y eficiente. Este artículo resume la evaluación de esta base de datos para documentar un buen ejemplo de cómo los marcos de evaluación en salud pública pueden llevar a mejorar la información en los sistemas de vigilancia contribuyendo de esta manera al objetivo final de mejorar la salud pública.

Percepción de la cantidad de flujo menstrual y su asociación con las deficiencias de hierro, ácido fólico y vitamina B12 en mujeres de la ciudad de méxico / Menstrual Bleeding perception and its association with iron, folic acid and vitamin B12 deficiencies among women from mexico city

La anemia de origen nutricio afecta a un tercio de las mujeres en edad reproductiva a nivel mundial y puede deberse a la deficiencia de uno o varios nutrimentos involucrados en la hematopoyesis, principalmente el hierro. Las mujeres constituyen un grupo en riesgo dadas las pérdidas menstruales. Por ello, el objetivo de este trabajo fue evaluar la relación entre la percepción de cantidad de flujo menstrual y las deficiencias de hierro, folato y vitamina B12 en una muestra de mujeres de la Ciudad de México. Se realizó un estudio transversal, con mujeres de 12 a 49 años, no embarazadas ni amamantando. Se midieron las concentraciones de hemoglobina, ferritina, hierro y vitamina B12 en suero y ácido fólico eritrocitario. La cantidad de flujo menstrual percibida se examinó con una escala analógica visual de 10 cm de longitud. Las asociaciones se evaluaron mediante las pruebas T de Student, Chi² y el coeficiente de correlación de Pearson. La sensibilidad y especificidad se representaron en una curva ROC. Los resultados mostraron que las anémicas tuvieron una percepción de la cantidad de flujo menstrual significativamente mayor que las no anémicas (p<0.05). No se observaron diferencias en las calificaciones informadas por las mujeres con deficiencias de otros nutrimentos y aquellas sin deficiencias. La escala analógica visual propuesta en este trabajo puede ser utilizada en poblaciones sanas como una herramienta subjetiva de tamizaje para el riesgo de padecer anemia, que además es fácil de contestar y económica(AU)

Nutritional anaemias affect more than one third of women of reproductive age worldwide as a result of a lack of one or various nutrients involved in the haematopoiesis, mainly iron. Women are at higher risk because of menstruation. The objective of this paper was to evaluate the association between the perception of the amount of menstrual bleeding and iron, folic acid, vitamin B12, ferritin and hemoglobin deficiencies, among women from Mexico City. This cross-sectional study included 12-49 year old women, that were not pregnant or breastfeeding. Hemoglobin, ferritin, iron, folate, and vitamin B12 were quantified. Self reported menstrual bleeding was estimated by using a 10 cm long visual analogue scale. Associations were calculated by Student’s T test, Chi2 and Pearson’s correlation coefficient. Sensibility and specificity were depicted in a ROC curve. Results showed that anaemic women perceived a larger menstrual blood loss than those non anaemic (p<0.05). No differences were observed in any other of the micronutrients studied.The visual analogue scale is an easy-to-answer and cheap screening test that could be used in apparently healthy populations to detect the risk of anaemia(AU)

Las conductas alimentarías de riesgo no se asocian con deficiencias de micronutrimentos en mujeres en edad reproductiva de la Ciudad de México / Abnormal eating behaviours are not associated with micronutrient deficiencies among women of childbearing age from Mexico City

El objetivo de este trabajo fue evaluar la asociación entre las conductas alimentarias de riesgo (CAR) y las deficiencias de vitaminas y nutrimentos inorgánicos en una muestra de mujeres en edad reproductiva. Participaron 282 mujeres de 12 a 49 años (21.9 por ciento adolescentes) no embarazadas ni lactando, muestreadas de manera sistemática con arranque aleatorio en 6 colonias del poniente del Distrito Federal. Se evaluaron las concentraciones de las vitaminas A, C, E, B12 y ácido fólico así como de hemoglobina, ferritina y hierro y zinc séricos. Para las CAR se usó un cuestionario validado en la población mexicana. La información se analizó con estadística descriptiva y la prueba de Fisher. Aproximadamente el 68 por ciento de la muestra fue de nivel socioeconómico medio-bajo o inferior. El 14.8 por ciento tuvo un puntaje de riesgo para las CAR, sin diferencias entre adolescentes y adultas. Las CAR más frecuentes fueron la preocupación por engordar y comer demasiado. El 10 por ciento de las mujeres, aproximadamente, usaron diuréticos o laxantes durante el trimestre anterior a la encuesta. Las deficiencias más importantes fueron las de Vitamina E, zinc y hierro, que afectan al 47 por ciento, 44 por ciento y 27 por ciento de la población, respectivamente. No hubo asociación significativa entre las CAR y las deficiencias de micronutrimentos de manera global ni al analizar por conductas aisladas. A pesar de ello, y dada la alta prevalencia de las CAR y la obesidad en esta población, es necesario hacer campañas para promover la adopción de conductas saludables que permitan alcanzar un peso adecuado.

The aim of this study was to evaluate the association between the risk of abnormal eating behaviors (AEB) and vitamin and mineral deficiencies among women. Women of childbearing age (n=282) were systematically sampled with a random start (21.9 percent adolescents) in 6 suburbs in the west side of Mexico City, they were non pregnant or breastfeeding. Vitamin A, C, E, B12, folic acid, hemoglobin, ferritin, cupper, iron and zinc concentrations were measured. A questionnaire validated in the Mexican population was used for screening AEB. Data were analyzed by descriptive statistics and by using Fisher´s test. Approximately 68 percent of the sample belonged to a mid-low or lower socioeconomic status. 14 percent had risk of AEB, without statistical differences between adults and teenagers. 10 percent used diuretics or laxatives to reduce weight within the trimester preceding the survey. Vitamin E, zinc and iron were the most widespread deficiencies affecting 47 percent, 44 percent and 27 percent of the population, respectively. There was no association between the AEB and micronutrient deficiencies neither when AEB were analyzed globally nor individually. Considering these results and the high prevalence of the AEB and overweight in this population, it is important to promote the adoption or healthy behaviors to achieve an adequate weight.

Racionalidad científica, causalidad y metaanálisis de ensayos clínicos / Scientific rationality, causality and metaanalyses of clinical trials

En el campo de la salud las revisiones sistemáticas y el metaanálisis (MA) han cobrado auge, ya que permiten congregar estudios de características similares y generar indicadores que describan el riesgo o el beneficio de intervenciones clínicas asociadas a la presencia de un problema de salud. Para interpretar el MA y darle su justa dimensión, es necesario tomar en cuenta la racionalidad del marco teórico que lo sustenta, sus criterios metodológicos y la posible relación causal entre exposición y evento, además del contextualizar la información. Actualmente, un gran reto constituye el análisis y la síntesis de la mayor cantidad de información para tomar decisiones de manera rápida y asertiva Este artículo hace un breve recorrido por la racionalidad científica y su aplicación en la teoría causal en el marco de la epidemiología, para sentar los cimientos que permitan evaluar la pertinencia y validez de las decisiones que se tomen con base en estos análisis.

Currently, the challenge is to analyze and synthesize as much information as possible in order to make quick, correct decisions. Systematic reviews and meta-analysis have quickly arisen in the health field because they allow researchers to congregate studies of similar characteristics to generate estimators that describe the risk or benefit of practices related to health problems. To understand and attach the appropriate importance to meta-analyses, it is necessary to consider the rationale of the theoretical framework, the methodological criteria, and the possible causal relationship between exposure and outcome, besides contextualizing the information. This paper briefly explores scientific rationality and its application in causal theory within an epidemiological framework, to set the basis that allows decision-makers and health professionals to evaluate the appropriateness and validity of conclusions derived from this type of analyses.