Journal of Midwifery & Women’s Health

Original Research

Rate of Low Vitamin D Levels in a Low-Risk Obstetric Population Lisa D. Kaloczi, CNM, DNP, WHNP, Angela Deneris, CNM, PhD

Introduction: The objectives of this study were to determine vitamin D levels at the first prenatal visit in women who had no obstetric risk factors and, if determined to have a low vitamin D level, to evaluate how high-dose treatment affected the vitamin D level by the end of the second trimester. Methods: This study was a descriptive, retrospective chart review. Women were identified through electronic database query based on prenatal care initiation. One hundred and four women had a 25-hydroxy (OH) vitamin D (25[OH]D) serum level drawn at the first prenatal visit. Supplementation was recommended with either 2000 or 4000 units of vitamin D3 for women who had vitamin D insufficiency or deficiency. Twenty women who were treated had repeat vitamin D levels drawn at 28 weeks’ gestation to evaluate the effectiveness of supplementation. Results: Descriptive analysis of demographic data of 104 women who had 25(OH)D levels drawn determined there were no significant differences between women who were vitamin D deficient or insufficient and those whose serum levels were in the sufficient range. Vitamin D serum levels revealed that 32 (30.8%) were sufficient (⬎30 ng/mL), 49 (47.1%) were insufficient (20-29 ng/mL), and 23 (22.1%) were deficient (⬍20 ng/mL). Twenty women had a repeat measure of 25(OH)D after supplementation, and there was a significant rise in vitamin D level (P ⬍ .001) with vitamin D3 supplementation. However, women who took 4000 units had a higher mean rise (13.17 ng/mL) in 25(OH)D than those taking 2000 units (8.79 ng/mL). Twelve of the women (60%) were still insufficient after supplementation with 2000 units of vitamin D3 . Discussion: This small sample of women demonstrates a significant degree of insufficiency and deficiency in this desert community where sunshine is plentiful. A larger study should be completed to determine ideal supplementation during pregnancy. c 2014 by the American College of Nurse-Midwives. J Midwifery Womens Health 2014;59:405–410  Keywords: vitamin D, pregnancy, deficiency, insufficiency, supplementation


Although vitamin D has traditionally been labeled a vitamin, it is actually a potent hormone involved in countless principal functions.1 Hormonal activity of vitamin D includes classic functions such as calcium regulation and bone formation in the body, yet it also influences a vast array of other tissues including the fetal brain and placenta during pregnancy.2 These multicellular and tissue activities may explain the associations noted between low vitamin D levels during pregnancy and later chronic illness in offspring.2 The National Health and Nutrition Examination Survey (NHANES)3 reported that from 2001 to 2004 more than 90% of the more pigmented population in the United States was vitamin D deficient, including black, Hispanic, and Asian individuals. White individuals had a deficiency rate of more than 75%.3 The prevalence has nearly doubled in the last 10 years according to this survey. The NHANES survey uses a nested cross-sectional design to gather information from a nationally representative probability sample of 5000 participants yearly. Demographic data were gathered through interview, and blood samples were gathered on-site by mobile clinics. The prevalence of vitamin D deficiency in pregnancy is 5% to 50% in some areas of the United States, which has generated interest in how vitamin D deficiency might cause adverse maternal and fetal outcomes.4 Some reasons for the increas-

ing rates of deficiency may be the rising numbers of immigrants (especially darkly pigmented individuals), successful campaigns for sun protection including avoidance and sunscreen use, less outdoor activity, and poor diet or lack of vitamin D in commonly eaten foods.3, 5 This study determined the prevalence of vitamin D insufficiency and deficiency in a low-risk population of pregnant women who live in a region of the United States that has approximately 240 days of sunlight annually.6 In addition, the study evaluated whether 2000 or 4000 units of vitamin D significantly elevated 25hydroxyvitamin D (25[OH]D) during pregnancy. Background

Address correspondence to Lisa D. Kaloczi, CNM, DNP, WHNP, 1254 Hudson Avenue, Salt Lake City, UT 84106. E-mail: [email protected]

Vitamin D deficiency has been purported to be associated with preeclampsia, gestational diabetes, primary cesarean birth, low birth weight, intrauterine growth retardation, and premature labor in multiple studies.2, 4, 7–18 In addition, low vitamin D levels during pregnancy and lactation have been linked to rickets, asthma, types 1 and 2 diabetes, hypertension, some cancers, multiple sclerosis, schizophrenia, depression, bipolar disorder, and other conditions in the offspring.1, 4, 7–18 Vitamin D levels can be estimated in the serum of individuals using several measures, but the most accurate is 25[OH]D. This level can be measured in nanograms per milliliter or nanomoles per liter, with 1 ng/mL equal to 2.5 nmol/L. There is some controversy about what constitutes an acceptable level of 25(OH)D to define vitamin D sufficiency versus deficiency, as well as whether the same levels are adequate in pregnancy. Many cutoff levels have

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c 2014 by the American College of Nurse-Midwives 


✦ Midwives should consider screening for vitamin D deficiency in women who spend most of their day indoors, wear

sunscreen consistently, have few sources of vitamin D in their diet, or have a family history of osteoporosis in the first trimester of pregnancy. ✦ There was a significant rise in vitamin D level (P ⬍ 0.0001) with vitamin D3 supplementation; however, women with vitamin D deficiency who took 4000 units had a greater mean rise than those taking 2000 units. ✦ Women diagnosed with vitamin D insufficiency or deficiency during pregnancy may require supplementation of 4000 units of vitamin D3 to reach sufficiency.

been proposed, and this may account for the discrepancies in prevalence.19 Generally, vitamin D insufficiency is defined as a serum 25(OH)D level less than 32 ng/mL (⬍80 nmol/L), and deficiency is defined as less than 20 ng/mL (⬍50 nmol/L), and the same levels are used in pregnant and nonpregnant women at this time.18 Toxicity can be defined by a 25(OH)D level of at least 150 ng/mL. Symptoms of toxicity include fatigue, nausea, vomiting, and unexplained weakness.20 Because of the continuous use and breakdown of vitamin D in the body, it is very difficult to acquire toxic levels. With a 25(OH)D level of at least 30 ng/mL, there is increased absorption of calcium in the intestine, thereby promoting bone mineralization and strength, and improved health outcomes, which explains the push for serum 25(OH)D levels greater than 30 ng/mL.21, 22 The impact of vitamin D deficiency and insufficiency during pregnancy is unclear. Few studies exist to determine supplementation needs during pregnancy. In addition, studies are needed to determine optimal timing of vitamin D screening, supplementation dosage, and when to recheck the level. Yu et al23 completed a prospective randomized study in London including 180 pregnant women beginning at 27 weeks’ gestation who were randomized to 1) daily (800 units/day), 2) one-time (200,000 units once), or 3) no treatment for vitamin D deficiency. The findings included a significant increase in 25(OH)D serum levels in the 2 groups of women who took supplements but no change in the women who were not in the supplemented group (P ⬍ .001); however, there was no significant difference in the increase of 25(OH)D levels between the 2 supplemented groups (P = .5). Also of note, only 30% of the women who took supplements attained sufficient vitamin D levels, and only 8% of infants were born with sufficient levels in the treatment groups. This leads to the question: What dose of vitamin D is necessary to raise 25(OH)D levels appropriately, and for how long should supplementation be continued? The largest double-blind randomized controlled trial of vitamin D supplementation in pregnancy was completed in 2011 by Hollis et al with a cohort of 350 women.24 Supplementation with 400, 2000, or 4000 units of vitamin D3 was found to increase serum 25(OH)D levels to sufficiency in 52.3%, 79.5%, and 83.9% of each group, respectively, within one month of birth (P ⬍ .001). The daily recommendation of 400 units of vitamin D at the time this study commenced was shown to increase 25(OH)D baseline by a mean of 5 ng/mL in participants over the course of the study, whereas supplementing with 2000 to 4000 units daily raised levels more 406

profoundly. Safety was evaluated in all patients via measurement of serum and urine calcium levels as well as symptomatology. None of the study participants developed any symptoms of toxicity. The Institute of Medicine (IOM) recently reviewed focused vitamin D research, including but not limited to the relationship between vitamin D deficiency and cancer, cardiac disease and high blood pressure, diabetes, falls, immune function, psychological function, preeclampsia, and reproductive health. The 2010 report summarizing this work did not find current evidence compelling enough to document a relationship between vitamin D deficiency and adverse health outcomes beyond the well-known relationship to bone health.19 The IOM also reports that, with little exception, the population of North America is getting enough vitamin D, and high levels of supplementation may be dangerous. Supplementation beyond 4000 units is not recommended in any population at this time; however, the recommended daily intake was increased from 400 to 600 units. Documentation of a definitive link between vitamin D deficiency and poor maternal and fetal outcomes waits additional research. Initially, however, the prevalence of vitamin D deficiency in pregnant women needs to be determined. Using retrospective chart review, the purpose of the study was to determine the prevalence of vitamin D insufficiency or deficiency in a low-risk pregnant population at the first prenatal visit at a midwifery clinic in the Salt Lake Valley. If women were determined to have a low vitamin D level, it was reviewed whether treatment for this condition during pregnancy significantly raised the vitamin D level by the end of the second trimester using high-dose vitamin D3 supplementation (≥2000 units/day). METHODS

This study was a descriptive, retrospective chart review of 426 healthy, low-risk pregnant women who presented for prenatal care between June 1, 2009, and December 31, 2011, to a midwifery practice in Salt Lake City, Utah. Through an electronic query of the computerized scheduling database, women were identified who had presented to the Birthcare Healthcare Nurse-Midwifery Practice for initiation of prenatal care during this time. There is currently no protocol for offering women screening for vitamin D deficiency in pregnancy at the Birthcare Healthcare practice. Five of 16 certified nurse-midwife (CNM) providers offer 25[OH]D screening with the first prenatal laboratory tests, whereas Volume 59, No. 4, July/August 2014

the others do not regularly offer this screening. For the purposes of this study, the 25(OH)D levels used were those defined by the University of Utah Associated Regional and University Pathologists laboratory: 25(OH)D sufficiency is at least 30 ng/mL; insufficiency is 20 to 29 ng/mL; deficiency is less than 20 ng/mL; and possible toxicity occurs at 150 ng/mL or greater. Women in this practice who had either vitamin D insufficiency or deficiency were advised to take either 2000 or 4000 units of vitamin D3 supplementation throughout the pregnancy and to increase their dietary sources of vitamin D. Inclusion criteria for this study included provision of care at one of 2 Birthcare Healthcare nurse-midwifery clinics and having had a serum 25(OH)D level drawn during the pregnancy. The exclusion criterion for this study was absence of a 25(OH)D level. Institutional review board approval was granted from the University of Utah for this study prior to initiation of chart reviews. Demographic data for age, height, weight, body mass index (BMI), gestation, ethnicity, medical history, and birth outcome were obtained. Data points were gathered in a deidentified Excel spreadsheet. Using Statistical Package for the Social Sciences Software (SPSS), descriptive statistics were computed as well as correlations using Spearman’s rho. Tests of withinparticipants effects and between-participants effects were also completed using ANOVA. RESULTS

Four hundred and twenty-six women were identified who met criteria for initial chart review. A thorough review revealed that 104 of the 426 women seen during the study period had an initial serum 25[OH]D level drawn. Demographic characteristics of the 104 women who had serum 25[OH]D levels drawn are listed in Table 1. There was no correlation between vitamin D level (ng/mL) and age, height, weight, BMI, gravidity, or parity after Spearman rho correlations were evaluated. Of the 104 women who consented to have 25(OH)D levels drawn at their first prenatal visit, 32 (30.8%) were in the normal range (⬎30 ng/mL), 49 (47.1%) were insufficient (2029 ng/mL), and 23 (22.1%) were deficient (⬍20 ng/mL). All 49 women who were insufficient and 23 women who were deficient were advised to increase vitamin D in their diets and to take 2000 to 4000 units of vitamin D3 daily. Of these women initially screened, 20 women (12 who were insufficient and 8 who were deficient) took a vitamin D supplement and had a second blood level obtained at 28 weeks’ gestation to evaluate effectiveness. Mean (SD) gestation was 10.7 (6.17) weeks at the time of the first analysis and 26.8 (4.74) weeks for the second analysis. The mean time between testing was 115.85 (38.60) days. The mean vitamin D level of the 20 women who had 2 values obtained was 20.85 (5.3) ng/mL at the initial assessment, and it was 30.95 (8.3) ng/mL at the second assessment. Five of the 8 women with vitamin D deficiency took 4000 units and had a mean rise in serum 25(OH)D of 15.8 ng/mL (range, 13-24 ng/mL increase); 3 of the 8 women with deficiency took 2000 units, and the mean increase was 16.3 ng/mL; 11 of 12 women with insufficiency took Journal of Midwifery & Women’s Health r

Table 1. Demographic Characteristics (N = 104)

Women Who Had Demographic

Total Cohort

a Second Vitamin D


(N = )

Analysis (n = )






Pacific Islander



Ethnicity, n White

Age, mean (SD), y

30.63 (4.39)

30.4 (4.39)

Height, mean (SD), in

65.41 (2.57)

64.93 (2.61)

Prepregnancy weight,

158.1 (32.61)

154.15 (31.02)

25.98 (5.18)

25.71 (4.74)

mean (SD), lb BMI, mean (SD), kg/m2 Parity, n (%) Nulliparous

43 (41.3)


39 (37.5)

8 (40)


22 (21.2

3 (15)

40 (1.48)

39 (1.74)

12.7 (7.55)

10.7 (6.17)

Gestation at birth,

9 (45)

mean (SD), wks Gestation at vitamin D testing, mean (SD), wks Abbreviation: BMI, body mass index.

2000 units and had a mean increase in serum 25(OH)D of 6.72 ng/mL (range, −2 to 17 ng/mL change); and the remaining woman with insufficiency took 4000 units and had no change in 25(OH)D from time 1 to time 2 (24 ng/mL); see Figure 1. Of 8 women with initial vitamin D deficiency, 2 (one who took 2000 units and one who took 4000 units of vitamin D3 ) were above the recommended 25(OH)D level of 30 ng/mL by 28 weeks’ gestation. The remaining 6 women were no longer deficient and were in the insufficient range (24-29 ng/mL). Of the 12 women found to be in the insufficient range initially, 6 increased their levels to the normal range, above 30 ng/mL, with 2000 units of vitamin D3 supplementation. The remaining 6 women in the insufficient group continued to be insufficient after treatment with 2000 units of vitamin D3 supplementation. Although there was not a significant difference between groups, the 4000 units group had a greater mean increase (Figure 2). One participant taking 4000 units had no change and 2 women taking 2000 units had negative changes in their 25(OH)D levels, questioning adherence to supplementation. DISCUSSION

Salt Lake City, Utah, is at 40.7 degrees latitude, 4200 feet elevation, and is considered a desert environment with an average of 240 days of sunshine annually.6 Although this is a small sample size of 104 pregnant women, it is significant that 69.2% of this healthy, low-risk, nonsmoking, mostly white cohort were found to have vitamin D insufficiency (47.1%) or deficiency (22.1%) at their initial prenatal visit. 407

Women consented for a 25(OH)D level at first prenatal visit (N=104)

Vitamin D sufficient N=32

Vitamin D deficient N=23

Vitamin D insufficient N=49

Recommended increased vitamin D3 to 2000-4000 units daily supplementation

No Recommended Changes

Women consented for repeat 25(OH)D level at 28 weeks (N=20)

Initially vitamin D insufficient (N=12)

Initially vitamin D deficient (N=8)

2000 units

4000 units

2000 units

4000 units





m increase 0 ng/mL

m increase 16.3 ng/mL

m increase 15.8 ng/mL


m increase 6.72 ng/mL

6 sufficient after supplementation

6 insufficient after supplementation

2 sufficient after supplementation (1 2000 units and 1 4000 units)

6 insufficient after supplementation

Figure 1. Algorithm for Screening and Treating Women for Vitamin D Insufficiency and Deficiency in Pregnancy a

Mean increase in vitamin D level from 25(OH)D time 1 to time 2.

This group of women would not have been considered high risk for low vitamin D levels and therefore would not meet the criteria for screening by the 2011 committee opinion by the American College of Obstetricians and Gynecologists (ACOG).25 Collins-Fulea et al26 completed a study of vitamin D deficiency prevalence in Detroit, Michigan, finding a large number of Indian, African American, Hispanic, Asian, and Middle Eastern women to be either insufficient or deficient. They also found that 79.2% of white women enrolled in their study (514 of 649) had vitamin D levels less than 30 ng/mL during pregnancy. This rate of vitamin D insufficiency and deficiency is higher than that reported by Mulligan et al4 of 5% to 50% and is likely a result of the northern latitude and seasonal variance. The incidence of deficiency or insufficiency in our population was 69.2%.


The function of vitamin D in pregnancy is still largely unknown and may be quite complex. Research about the impact of low vitamin D levels in pregnancy is conflicting and not compelling enough to significantly change current IOM recommendations.7 However, the total daily recommendation of 600 units vitamin D intake may not be enough to sufficiently raise the vitamin D level during pregnancy if women are found to be deficient. During our study, 25(OH)D levels improved by a mean of 13.2 ng/mL in the 6 women taking 4000 units of vitamin D3 daily over approximately 16 weeks. Women in both the 2000 units/day group and the 4000 units/day group had significant increases in their 25(OH)D levels, but only 8 of 20 women (40%) had levels higher than 30 ng/mL at the time of the second test. This finding was similar to that in the trial by Hollis et al.24 They found that high-dose vitamin D supplementation

Volume 59, No. 4, July/August 2014

Average Increase in Vitamin D Level a

nancy, given the high vitamin demands of pregnancy and the significant physiologic changes of hemodilution during the late second trimester. CLINICAL IMPLICATIONS

We recommend that all practitioners consider screening women in the first trimester of pregnancy for vitamin D deficiency if the women spend most of their day indoors, live in a northern state, have darkly pigmented skin, wear sunscreen consistently, have few sources of vitamin D in their diet, or have a family history of osteoporosis. Daily supplementation with 2000 to 4000 units may be indicated if women are insufficient or deficient in 25(OH)D levels.

2000 units

CONCLUSION 4000 units

Time 1

Time 2

Figure 2. Difference Between Rise in 25 Hydroxyvitamin D Between Time 1 and Time 2 with Supplementation of 2000 or 4000 units of Vitamin D3 a Average increase in vitamin D level was measured in nanograms per milliliter of 25(OH)D.

(⬎2000 units daily) was effective at elevating 25(OH)D, but 2000 units was not significantly more effective than 4000 units daily. It can be presumed that if both groups in our study had continued with their vitamin D intake, this trend would have continued, and most women would be at normal levels by term. The sample size was too small to determine if supplementation influenced pregnancy outcome, and therefore, this was not a goal of this study. The Endocrine Society clinical guideline recommends considering screening and treating vitamin D deficiency of women during pregnancy and lactation. Supplementation as high as 4000 units daily has been recommended to improve vitamin D levels, with repeat testing to evaluate effectiveness every 3 months.27 Considering the role of vitamin D in bone health and muscle contractility, at a minimum vitamin D deficiency should be diagnosed early in prenatal care and treated with high-dose vitamin D. A strength of this study was that there was consistency in recommending high-dose vitamin D supplementation among the CNMs in this practice. The limitations of the study included a small convenience, retrospective sample, lack of ethnic diversity, and that the women were not screened for their use of sunscreen, sun exposure, or dietary sources of vitamin D. Another limitation is seasonal variance; vitamin D levels can vary greatly by season, and these levels were drawn throughout the year. In addition, we did not know for certain if the women in the study diagnosed with vitamin D insufficiency or deficiency took the recommended supplementation or their prenatal vitamins. Indeed, one participant had no change, and 2 women had negative changes in their 25(OH)D levels, questioning adherence to supplementation. Another limitation of current studies is that there are no known baseline standard values for vitamin D levels throughout pregJournal of Midwifery & Women’s Health r

Additional prospective studies are needed to determine the significance of vitamin D insufficiency or deficiency on pregnancy and neonatal outcomes and if high-dose vitamin D supplementation to elevate levels would significantly affect outcomes. Further studies are also needed to quantify the appropriate amount of vitamin D that is safe and effective to improve the vitamin D levels in pregnancy. Future studies should include a larger, more diverse sample to consider vitamin D absorption and metabolism when determining need for screening, testing, and supplementation. Considering that pregnancy is a crucial time for the mother to have adequate nutritional intake for the future health of the developing fetus, vitamin D may be determined to play a significant role in optimizing outcomes. AUTHORS

Lisa D. Kaloczi, CNM, DNP, WHNP, is an Assistant Professor at the University of Utah. She teaches advanced pharmacology for women’s health in the women’s health nurse practitioner and nurse midwifery programs and is active in the faculty clinical practice as a CNM. Angela Deneris, CNM, PhD, FACNM, is a Professor, Clinical with the women’s health nurse practitioner and nurse midwifery program at the University of Utah as well as in clinical practice with the Birthcare Healthcare faculty practice in Salt Lake City, Utah. CONFLICT OF INTEREST

The authors have no conflicts of interest to disclose. ACKNOWLEDGMENTS

We acknowledge the work of Bob Wong, PhD, for his helpful feedback and assistance with data analysis. REFERENCES 1.Cannell JJ, Hollis BW. Use of vitamin D in clinical practice. Alt Med Rev. 2008;13(1):6-20. 2.Lapillonne A. Vitamin D deficiency during pregnancy may impair maternal and fetal outcomes. J Med Hypoth. 2009;74:71-75. 3.Ginde AA, Liu MC, Camargo CA Jr. Demographic differences and trends of vitamin D insufficiency in the US population, 1988–2004. Arch Intern Med. 2009;169:626-632.


4.Mulligan ML, Felton SK, Riek AE, Bernal-Mizrachi C. Implications of vitamin D deficiency in pregnancy and lactation. Am J Obstet Gynecol. 2009;201:e1-e9. 5.Ginde AA, Sullivan AF, Mansbach JM, Camargo, CA. Vitamin D insufficiency in pregnant and nonpregnant women of childbearing age in the United States. Am J Obstet Gynecol. 2010;202 (436): e1-e8. 6.“Annual Average Possible Sunshine.” National Climatic Data Center. National Oceanic and Atmospheric Administration, 2009. Accessed November 19, 2012. 7.Bodnar LM, Catov JM, Simhan HN, Holick MF, Powers RW, Roberts JM. Maternal vitamin D deficiency increases the risk of preeclampsia. J Clin Endocrinol Metab. 2007;92:35173522. 8.Bodnar LM, Krohn MA, Simhan HN. Maternal vitamin D deficiency is associated with bacterial vaginosis in the first trimester of pregnancy. J Nutr. 2009;139:1157-1161. 9.Bowyer L, Catling-Paull C, Diamond T, Homer C, Davis G, Craig ME. Vitamin D, PTH, and calcium levels in pregnant women and their neonates. Clin Endocrinol. 2009;70:372377. 10.Clifton-Bligh RJ, McElduff P, McElduff A. Maternal vitamin D deficiency, ethnicity, and gestational diabetes. Diab Med. 2008;25:678684. 11.Grant WB, Holick MF. Benefits and requirements of vitamin D for optimal health: a review. Alt Med Rev. 2005;10:94-111. 12.Haugen M, Brantsaeter AL, Trogstad L, et al. Vitamin D supplementation and reduced risk of preeclampsia in nulliparous women. Epidemiology. 2009;20:720-726. 13.Merewood A, Mehta SD, Chen TC, Bauchner H, Holick MF. Association between vitamin D deficiency and primary cesarean section. J Clin Endocrinol Metab. 2009;94:940-945. 14.Zhang C, Qiu C, Hu FB, et al. Maternal plasma 25-hydroxyvitamin D concentrations and the risk for gestational diabetes mellitus. PLoSONE. 2008;3:e3753. 15.Robinson CJ, Alanis MC, Wagner CL, Hollis BW, Johnson DD. Plasma 25-hydroxyvitamin D levels in early-onset severe preeclampsia. Am J Obstet Gynecol. 2010;203:e1-e6.


16.Oken E, Ning Y, Rifas-Shiman SL, Rich-Edwards JW, Olsen SF, Gillman MW. Diet during pregnancy and risk of preeclampsia and gestational hypertension. Ann Epidem. 2007;17: 663-668. 17.Maghbooli Z, Hossein-Nezhad A, Karimi F, Shafaei A, Larijani B. Correlation between vitamin D3 deficiency and insulin resistance in pregnancy. Diab/Metab Res Rev. 2008;24:27-32. 18.Holick MF, Chen TC. Vitamin D deficiency: A worldwide problem with health consequences. Am J Clin Nutr. 2008;87(Suppl):S1080S1084. 19.Institute of Medicine Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press; 2010. 20.Kulie T, Groff A, Redmer J, Hounshell J, Schrager S. Vitamin D: An evidence-based review. J Am Board Fam Med. 2009;22(6): 698-706. 21.Heaney RP, Dowell MS, Hale CA, Bendich A. Calcium absorption varies within the reference range for serum 25-hydroxyvitamin D. J Am Coll Clin Nutr. 2003;22:142-146. 22.Bischoff-Ferrari HA, Giovannucci E, Willett WC, Dietrich T, DawsonHughes B. Estimation of optimal serum concentrations of 25hydroxyvitamin D for multiple health outcomes. Am J Clin Nutr. 2006;84:18-28. 23.Yu CKH, Sykes L, Sethi M, Teoh TG, Robinson S. Vitamin D deficiency and supplementation during pregnancy. Clin Endocrin. 2009;70:685690. 24.Hollis BW, Johnson D, Hulsey TC, Ebeling M, Wagner CL. Vitamin D supplementation during pregnancy: double-blind, randomized clinical trial of safety and effectiveness. J Bone and Min Res. 2011;26(10):2341-2357. 25.Vitamin D. Screening and supplementation during pregnancy. Committee Opinion No. 495. American College of Obstetricians and Gynecologists. Obstet Gynecol. 2011;118:197-198. 26.Collins-Fulea C, Klima K, Wegienka GR. Prevalence of vitamin D deficiency in an urban Midwestern obstetric practice. J Midwifery Womens Health. 2012;57:439-444. 27.Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, treatment, and prevention of vitamin D deficiency: an endocrine society clinical practice guideline. J Clin Endocrin and Metab. 2011;96(7):1911-1930.

Volume 59, No. 4, July/August 2014

Rate of low vitamin D levels in a low-risk obstetric population.

The objectives of this study were to determine vitamin D levels at the first prenatal visit in women who had no obstetric risk factors and, if determi...
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