January 23, 2017
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Nutrition during pregnancy affects the growing fetus, and identifying appropriate nutritional supplementation in pregnancy has been a hot topic for decades. Vitamin B12 is an essential nutritional component found only in animal derived products like meat, milk and eggs. Low intake of such products increases the risk of vitamin B12 deficiency. The proportion of pregnant women with vitamin B12 deficiency ranges from a small percentage in some Western countries, like Norway, to over two thirds in developing countries, such as India. In a newly published paper, all previous studies on effects of vitamin B12 levels in pregnancy were evaluated and their results pooled in a meta study. The question asked was whether vitamin B12 deficiency during pregnancy was harmful for the fetus?
Low birth weight and preterm birth are two potentially harmful outcomes of pregnancy. Worldwide, low birth weight and preterm birth are responsible for half of all deaths within the first 28 days after birth. Many studies have evaluated whether low levels of vitamin B12 during pregnancy is associated with low birth weight and preterm birth. Some studies found an association, others have not. In a multi-center study, primarily based at the Norwegian University of Science and Technology (NTNU), Norway, Yale University School of Public Health, and Erasmus Medical Center, the Netherlands, researchers set out to systematically summarize current knowledge on this topic.
Results from the analysis were just published in the American Journal of Epidemiology. 18 studies from 11 different countries including 11,216 pregnancies were evaluated. Overall, results showed that low levels of maternal vitamin B12 during pregnancy did not affect newborn birth weight. However, vitamin B12 deficient women carried a 21% increased risk of preterm birth compared with non-deficient women. These results were similar in high-, low- and middle-income countries.
The researchers underscore that there may be other reasons for the apparent association between vitamin B12 deficiency and preterm birth. Lead author Dr. Tormod Rogne, PhD candidate at the Department of Public Health and General Practice at NTNU, points out that low levels of vitamin B12 may be associated with other factors, such as undernutrition and poverty, that may affect newborn weight and length of pregnancy. He adds that based on these results, there is insufficient evidence to support routine supplementation of vitamin B12 during pregnancy to improve birth weight and length of gestation. To date, only two small and inconclusive intervention trials have been conducted that evaluate vitamin B12 supplementation during pregnancy and risk of low birth weight and preterm birth. In his opinion, larger trials need to be conducted, and all trials, published and unpublished, will then have to be synthesized in a systematic review. The hope, he concludes, is that their paper will encourage the conduct of these future trials. Michael B. Bracken, the Susan Dwight Bliss Professor Emeritus of Epidemiology and former Professor of Obstetrics, Gynecology & Reproductive Sciences at Yale Schools of Public Health and Medicine added: “These systematic reviews of existing evidence are essential before embarking on massive intervention and supplementation trials and we have done that for vitamin B12”.
Other authors on the study include senior author Dr. Kari R. Risnes from the Department of Public Health and General Practice at NTNU; Dr. Oscar H. Franco, Professor of Preventive Medicine, Department of Epidemiology at Erasmus MC; Dr. Myrte J. Tielemans, Department of Medical Microbiology and Infectious Diseases at Erasmus MC; and 19 others. The study was funded by NTNU as part of the PhD in Medicine program and supported by the Yale Center for Perinatal Pediatric and Environmental Epidemiology.
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A recent Yale School of Public Health analysis identified 55 known, probable or possible human carcinogens determined to be potential water or air pollutants from the fracking process.
Read more in the Yale Daily News.
Julie Kezik and Melissa Hill, Cambridge University Press , June 2016.
Authored by Julie Kezik and Melissa Hill and Published by Cambridge University Press , June 2016.
SAS programming is a creative and iterative process designed to empower you to make the most of your organization's data. This friendly guide provides you with a repertoire of essential SAS tools for data management, whether you are a new or an infrequent user. Most useful to students and programmers with little or no SAS experience, it takes a no-frills, hands-on tutorial approach to getting started with the software. You will find immediate guidance in navigating, exploring, visualizing, cleaning, formatting, and reporting on data using SAS and JMP. Step-by-step demonstrations, screenshots, handy tips, and practical exercises with solutions equip you to explore, interpret, process and summarize data independently, efficiently and effectively.
About the authors:
Julie Kezik is a biostatistician at the Yale Center for Perinatal, Pediatric, and Environmental Epidemiology. Her primary research interests are assessing the effects of indoor and outdoor air pollution on at-risk populations, and she currently focuses on providing statistical analysis and research support for epidemiological studies of environmental exposures and early childhood health outcomes. Kezik’s current work uses a combination of measured data, traffic information, and health outcomes to help create interventions that will improve health.
Melissa Hill is a clinical programmer at Cd3 Inc. where she uses SAS to perform and support the design and programming of clinical data structures related to drug development. Prior to her position at Cd3 Inc., she worked as an epidemiologist at the Yale Center for Perinatal, Pediatric, and Environmental Epidemiology. During that time, Hill used SAS to support her various roles at the CPPEE including programmer analyst, field study coordinator, and research associate. She enjoys sharing her diverse SAS experience with other members of her team and developing new ways to harness the broad range of tools that SAS provides.