ORIGINAL ARTICLE Parity and tanned white skin as novel predictors of vitamin D status in early pregnancy: a population-based cohort study L. B. Andersen* , †, B. Abrahamsen‡ , §, C. Dalg  ard¶, H. B. Kyhlk, S. S. Beck-Nielsen† , **, M. Frost-Nielsen†, J. S. Jørgensen††, T. Barington‡ , k , ‡‡ and H. T. Christesen* *Hans Christian Andersen Children’s Hospital, Odense University Hospital, †Institute of Clinical Research,University of Southern Denmark, ‡Odense Patient data Exploratory Network (OPEN), Odense University Hospital, Odense, §Department of Medicine F, Copenhagen University Hospital Gentofte Hospital, Hellerup, ¶Department of Environmental Medicine, Institute of Public Health, University of Southern Denmark, kOdense Child Cohort, Hans Christian Andersen Children’s Hospital, Odense, **Department of Pediatrics, Hospital of Southwest Denmark, Esbjerg, ††Department of Obstetrics and Gynaecology, Odense University Hospital and ‡‡Department of Clinical Immunology, Odense University Hospital, Odense, Denmark Abstract Context In pregnancy, vitamin D insufficiency and deficiency, defined as serum 25-hydroxyvitamin D (25(OH)D) <50 nM, and <25 nM, respectively, may have adverse effects for both mother and child. Prevalence estimates, and identification of subgroups at special risk, may be useful for the planning of pre- ventive strategies. Objective To study the prevalence and risk factors of hypovita- minosis D in early pregnancy. Design and Methods In a cross-sectional study of 1348 women in early pregnancy from the Odense Child Cohort, Den- mark, 25(OH)D was determined and correlated to demographic and lifestyle variables (age, nationality, skin tone, parity, prepre- gnancy body mass index (BMI), smoking and sun exposure), using multiple linear and logistic regression analyses for all year, or stratified for summer and winter. The risk of vitamin D insufficiency was expressed as odds ratios (OR) with 95% confi- dence intervals in brackets. Results The prevalence of vitamin D insufficiency and deficiency was estimated to 278% and 35% respectively. In adjusted analy- ses, vitamin D insufficiency was directly associated with winter season, OR = 189 (135–263); increasing prepregnancy BMI, OR = 106 (103–110); and smoking, OR = 27 (134–541); but was less frequent in nulliparous, OR = 047 (033–068) and tanned Caucasians, OR = 063 (041–097). Season-specific associ- ations having parental origin from outside Europe in summer, OR = 413 (141–1213); in winter smoking, OR = 315 (119– 836); and prepregnancy BMI, OR = 112 (106–118). Conclusions Vitamin D insufficiency was widespread in early pregnancy. Associations to smoking, prepregnancy BMI and origin outside Europe varied with season. Multiparity and not being tanned in Caucasians represent new risk factors of vitamin D insufficiency. (Received 31 October 2012; returned for revision 3 January 2013; finally revised 7 January 2013; accepted 7 January 2013) Introduction Vitamin D insufficiency and deficiency during pregnancy, here defined as serum 25-hydroxyvitamin D (25(OH)D) <50 nM, and 25(OH)D < 25 nM, respectively, have been associated to a number of pregnancy-related health issues. 1 These include pre- eclampsia, 2 gestational diabetes, 3 bacterial vaginosis 4 and post- partum depression. 5 Hypovitaminosis D in pregnancy may also have several health consequences for the offspring. 6 In the neo- nate, hypovitaminosis D can impair bone growth and minerali- zation, causing neonatal rickets or hypocalcaemic seizures. 7 Low birth weight, or weight small for gestational age, was also linked to poor vitamin D status in some, but not all studies. 6 A recent Cochrane review found some evidence that supplementation of vitamin D could decrease the risk of preterm birth. 8 Further- more, in observational studies, hypovitaminosis D in utero has been associated with better scores on psychomotor and mental development scales at age 14 months, 9 upper respiratory infec- tions, wheezing, rhinitis, eczema 10,11 and type 1 diabetes in adulthood. 12 Unfortunately, vitamin D insufficiency is found to be relatively common in adults as well as in pregnant women 13–16 with increasing prevalence at high latitudes due to lower solar UVB radiation, 17 and in dark-skinned or veiled women. 17,18 In Denmark (56 degrees North), vitamin D levels in pregnancy have only been investigated in two smaller observational stud- ies, 19,20 in which vitamin D insufficiency was present in 16–31% of subjects. At northern latitudes, insufficient solar UVB radia- tion for the skin production of vitamin D 3 renders 25(OH)D levels to be completely dependent on dietary intake from Correspondence: Henrik Thybo Christesen, Hans Christian Andersen Children’s Hospital, Odense University Hospital, Sdr. Blvd. 29, 5000 Odense C, Denmark. Tel.: +45 6541 1266; Fax +45 6591 1862; E-mail: henrik.thybo.christesen@ouh.regionsyddanmark.dk © 2013 John Wiley & Sons Ltd 333 Clinical Endocrinology (2013) 79, 333–341 doi: 10.1111/cen.12147