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Vitamin D insufficiency in women of childbearing age: Ginde et al
Journal Club
www. AJOG.org
Vitamin D insufficiency in women of childbearing age: Ginde et al George A. Macones, MD, MSCE, Associate Editor The article below summarizes a roundtable discussion of a study published in this issue of the Journal in light of its methodology, relevance to practice, and implications for future research. Article discussed: Ginde AA, Sullivan AF, Mansbach JM, Camargo CA Jr. Vitamin D insufficiency in pregnant and nonpregnant women of childbearing age in the United States. Am J Obstet Gynecol 2010;202:436.e1-8. The full discussion appears at www.AJOG.org, pages e1-3.
DISCUSSION QUESTIONS
What are the overall aims of the study?
How important is this question?
What is the NHANES dataset?
Can you describe this complicated analysis in simpler terms? What information is in the tables? What are the study’s strengths and weaknesses? What do we learn about vitamin D supplementation?
From the Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO: Moderator George A. Macones, MD, MSCE Professor and Chair Discussants Jennifer Allsworth, PhD Assistant Professor Lorie Harper, MD Fellow Katherine Goetzinger, MD Fourth-Year Resident 0002-9378/free © 2010 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2010.02.040
See related article, page 436
T
his month, Journal Club members discussed a very interesting article by Ginde et al. The work focused on vitamin D levels in women of child-bearing age—pregnant and not—in the United States. Experts have been reassessing optimal vitamin D intake; specifically, whether more is better. Currently, the Food and Nutrition Board at the Institute of Medicine of the National Academies is examining dietary reference intakes for vitamin D and calcium and is due to release a report by the end of summer 2010. One vital research area centers on how maternal levels of vitamin D relate to fetal development. Its influence on fetal bone formation is accepted, but maternal vitamin D levels may play a role in other aspects of fetal and child health. For example, some observational data suggest that inadequate maternal vitamin D status might predispose a child to asthma. In fact, in our department at Washington University in St. Louis, we are now recruiting participants for a randomized controlled trial that will test whether vitamin D supplementation in pregnancy might reduce the occurrence of childhood asthma. For all of the above reasons, Journal Club participants felt that this was an important study.
Who’s in charge? In late 2008, the American Academy of Pediatrics recommended that pregnant women be screened for vitamin D deficiency. Once again, we are confronted with an issue that crops up from time to time: who should be making recommendations about prenatal therapies and management of pregnancy? The same
question surfaced several years ago after the New England Journal of Medicine published a paper on subclinical hypothyroidism and infant neurodevelopment. After that, the American Society of Clinical Endocrinologists, the American Thyroid Society, and the Endocrine Society issued a joint recommendation for routine screening for hypothyroidism in women of reproductive age and pregnant women. Opinions may vary on this topic. However, I firmly believe that national recommendations for care in pregnancy should be made by those who provide primary care for pregnant women, including groups such as the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine. Certainly a role exists for joint opinions across societies, and we are seeing this increasingly in our specialty. But obstetricians should not feel compelled to follow “guidelines” that have been unilaterally written by nonobstetric societies. Rather, we should concentrate on guidelines written by our own professional societies.
NHANES The study by Ginde et al used a publicly accessible dataset compiled from the National Health and Nutrition Examination Survey (NHANES) as a substrate for their study. It is essential that readers understand a study’s data source, as this provides information about potential strengths and limitations of the research incorporating its data. In this case, the NHANES is a population-based survey that has been administered continuously since 1999 by the National Center for
MAY 2010 American Journal of Obstetrics & Gynecology
509
Journal Club
www.AJOG.org
Health Statistics, a division of the Centers for Disease Control and Prevention. It includes about 5000 people per year and samples from 15 different counties across the United States with the goal of achieving a nationally representative sample. Essentially, a survey team, consisting of a physician, medical technicians, and dietary and health interviewers, gathers information by visiting the participant’s home and conducting an interview on health status, disease history, activity, and diet. This is followed by a physical examination by a physician in the NHANES mobile examination center. Subjects also undergo measurements of blood pressure, height, and weight, bone
densitometry, a dental examination, and vision, hearing, and breathing tests. Urine and blood samples are collected. Transportation is provided to and from the mobile examination center to remove potential barriers to participation, and subjects are compensated for their time. Of the NHANES many strengths, the most notable are its nationally representative sample of subjects and the detailed cache of data obtained for each. A relative disadvantage for obstetric research is the relatively limited number of pregnant women included in the study.
Time for supplementation? This new study informs us that women of reproductive age have relatively low
vitamin D levels and that supplementation increases these levels. It does not tell us how much vitamin D is necessary in the reproductive years, how much is needed during pregnancy to optimize maternal and fetal outcomes, or whether we should provide additional vitamin supplementation in pregnancy. To answer those questions, we require carefully conducted observational studies that first assess maternal vitamin D levels in pregnancy and then relate those levels to neonatal outcomes. Such studies would then need to be followed by carefully conducted clinical trials that test specific hypotheses. Only then will we know whether additional vitamin D supplementation is warranted in pregnancy. f
Artwork guidelines To publish slides, tables, multimedia presentations, and other supplementary materials clearly, AJOG requires formats that meet standard requirements for sharp reproduction. When preparing a manuscript for submission, please refer to the checklist below:
✔ File format is *.tif, *.eps, *.jpg, or (if necessary) *.pdf ✔ Color images are RGB ✔ Image resolution is 300 dpi or greater ✔ Each image measures at least 4×6 inches exclusive of surrounding white space
✔ All lettering is at least 1/16 inch high ✔ Font is Helvetica ✔ Each figure or other item to be reproduced directly from your material is in its own file, numbered in the order of citation in the text
✔ Figure titles, legends, and footnotes (eg, keys to symbols in a figure)
are not in the files containing the figures, but follow the reference list after the text in the main file
For comprehensive artwork submission guidelines from Elsevier, our parent company, go to AJOG.org —> ONLINE SUBMISSION (at left) —> Artwork Guidelines (at right). Thank you.
510
American Journal of Obstetrics & Gynecology MAY 2010
www. AJOG.org
Vitamin D insufficiency in women of childbearing age: Ginde et al George A. Macones, MD, MSCE, Associate Editor The article below summarizes a roundtable discussion of a study published in this issue of the Journal in light of its methodology, relevance to practice, and implications for future research. Article discussed: Ginde AA, Sullivan AF, Mansbach JM, Camargo CA Jr. Vitamin D insufficiency in pregnant and nonpregnant women of childbearing age in the United States. Am J Obstet Gynecol 2010;202:436.e1-8. The full discussion appears at www.AJOG.org, pages e1-3.
DISCUSSION QUESTIONS
What are the overall aims of the study?
How important is this question?
What is the NHANES dataset?
Can you describe this complicated analysis in simpler terms? What information is in the tables? What are the study’s strengths and weaknesses? What do we learn about vitamin D supplementation?
From the Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO: Moderator George A. Macones, MD, MSCE Professor and Chair Discussants Jennifer Allsworth, PhD Assistant Professor Lorie Harper, MD Fellow Katherine Goetzinger, MD Fourth-Year Resident 0002-9378/free © 2010 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2010.02.040
See related article, page 436
T
his month, Journal Club members discussed a very interesting article by Ginde et al. The work focused on vitamin D levels in women of child-bearing age—pregnant and not—in the United States. Experts have been reassessing optimal vitamin D intake; specifically, whether more is better. Currently, the Food and Nutrition Board at the Institute of Medicine of the National Academies is examining dietary reference intakes for vitamin D and calcium and is due to release a report by the end of summer 2010. One vital research area centers on how maternal levels of vitamin D relate to fetal development. Its influence on fetal bone formation is accepted, but maternal vitamin D levels may play a role in other aspects of fetal and child health. For example, some observational data suggest that inadequate maternal vitamin D status might predispose a child to asthma. In fact, in our department at Washington University in St. Louis, we are now recruiting participants for a randomized controlled trial that will test whether vitamin D supplementation in pregnancy might reduce the occurrence of childhood asthma. For all of the above reasons, Journal Club participants felt that this was an important study.
Who’s in charge? In late 2008, the American Academy of Pediatrics recommended that pregnant women be screened for vitamin D deficiency. Once again, we are confronted with an issue that crops up from time to time: who should be making recommendations about prenatal therapies and management of pregnancy? The same
question surfaced several years ago after the New England Journal of Medicine published a paper on subclinical hypothyroidism and infant neurodevelopment. After that, the American Society of Clinical Endocrinologists, the American Thyroid Society, and the Endocrine Society issued a joint recommendation for routine screening for hypothyroidism in women of reproductive age and pregnant women. Opinions may vary on this topic. However, I firmly believe that national recommendations for care in pregnancy should be made by those who provide primary care for pregnant women, including groups such as the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine. Certainly a role exists for joint opinions across societies, and we are seeing this increasingly in our specialty. But obstetricians should not feel compelled to follow “guidelines” that have been unilaterally written by nonobstetric societies. Rather, we should concentrate on guidelines written by our own professional societies.
NHANES The study by Ginde et al used a publicly accessible dataset compiled from the National Health and Nutrition Examination Survey (NHANES) as a substrate for their study. It is essential that readers understand a study’s data source, as this provides information about potential strengths and limitations of the research incorporating its data. In this case, the NHANES is a population-based survey that has been administered continuously since 1999 by the National Center for
MAY 2010 American Journal of Obstetrics & Gynecology
509
Journal Club
www.AJOG.org
Health Statistics, a division of the Centers for Disease Control and Prevention. It includes about 5000 people per year and samples from 15 different counties across the United States with the goal of achieving a nationally representative sample. Essentially, a survey team, consisting of a physician, medical technicians, and dietary and health interviewers, gathers information by visiting the participant’s home and conducting an interview on health status, disease history, activity, and diet. This is followed by a physical examination by a physician in the NHANES mobile examination center. Subjects also undergo measurements of blood pressure, height, and weight, bone
densitometry, a dental examination, and vision, hearing, and breathing tests. Urine and blood samples are collected. Transportation is provided to and from the mobile examination center to remove potential barriers to participation, and subjects are compensated for their time. Of the NHANES many strengths, the most notable are its nationally representative sample of subjects and the detailed cache of data obtained for each. A relative disadvantage for obstetric research is the relatively limited number of pregnant women included in the study.
Time for supplementation? This new study informs us that women of reproductive age have relatively low
vitamin D levels and that supplementation increases these levels. It does not tell us how much vitamin D is necessary in the reproductive years, how much is needed during pregnancy to optimize maternal and fetal outcomes, or whether we should provide additional vitamin supplementation in pregnancy. To answer those questions, we require carefully conducted observational studies that first assess maternal vitamin D levels in pregnancy and then relate those levels to neonatal outcomes. Such studies would then need to be followed by carefully conducted clinical trials that test specific hypotheses. Only then will we know whether additional vitamin D supplementation is warranted in pregnancy. f
Artwork guidelines To publish slides, tables, multimedia presentations, and other supplementary materials clearly, AJOG requires formats that meet standard requirements for sharp reproduction. When preparing a manuscript for submission, please refer to the checklist below:
✔ File format is *.tif, *.eps, *.jpg, or (if necessary) *.pdf ✔ Color images are RGB ✔ Image resolution is 300 dpi or greater ✔ Each image measures at least 4×6 inches exclusive of surrounding white space
✔ All lettering is at least 1/16 inch high ✔ Font is Helvetica ✔ Each figure or other item to be reproduced directly from your material is in its own file, numbered in the order of citation in the text
✔ Figure titles, legends, and footnotes (eg, keys to symbols in a figure)
are not in the files containing the figures, but follow the reference list after the text in the main file
For comprehensive artwork submission guidelines from Elsevier, our parent company, go to AJOG.org —> ONLINE SUBMISSION (at left) —> Artwork Guidelines (at right). Thank you.
510
American Journal of Obstetrics & Gynecology MAY 2010