title: BMI and season are associated with vitamin D deficiency in women with impaired fertility: a two-centre analysis.
abstract: OBJECTIVE
  Animal and human studies suggest that vitamin D regulates functions of the reproductive system. Vitamin D deficiency is prevalent in women of reproductive age. Vitamin D status has been associated with in vitro fertilisation outcome, features of polycystic ovarian syndrome (PCOS) and endometriosis. The aims of our study were to investigate the prevalence of vitamin D deficiency of infertile women living in central Germany, to identify risk factors for vitamin D deficiency and to specify seasonal variations of vitamin D status.
  
  
  METHODS
  This was a retrospective cohort study at an academic tertiary care centre (N = 113) and an Outpatient Centre for Reproductive Medicine (N = 193) of women presenting for infertility treatment. The statistical evaluation was descriptive and explorative. Possible risk factors associated with an increased risk for vitamin D deficiency were assessed using multiple logistic regression models. Variables with p value less than 0.05 were further assessed in a multivariable logistic regression model.
  
  
  RESULTS
  Overall, 98.2 % of patients at centre 1 and 81.3 % of women with impaired fertility at centre 2 had deficient or insufficient vitamin D levels. Overweight BMI and limited exposure to sun (winter, spring and autumn trimester) were associated with an increased risk of vitamin D deficiency. Vitamin D levels did not vary according to age or infertility associated disorders (e.g. endometriosis, PCOS).
  
  
  CONCLUSIONS
  The rate of vitamin D deficiency among women with impaired fertility is alarming. Prospective studies are pressingly needed to confirm a causal relationship and to investigate the potential therapeutic benefits of vitamin D supplementation in this population.
authors.affiliation: Department of Obstetrics and Gynecology, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Dressler
authors.affiliation: Center for Reproductive Medicine Bad Münder, Hannoversche Straße 24, 31848, Bad Münder, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Chandra
authors.affiliation: Institute for Biostatistics, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Aguirre Dávila
authors.affiliation: Institute for Biostatistics, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany.
authors.forename: L M
authors.initials: LM
authors.lastname: Spineli
authors.affiliation: Department of Obstetrics and Gynecology, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Schippert
authors.affiliation: Department of Obstetrics and Gynecology, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany. frauke.von.versen@gmx.de.
authors.forename: F
authors.initials: F
authors.lastname: von Versen-Höynck
mesh_terms: D000328:Adult; D000818:Animals; D015992:Body Mass Index; D019587:Dietary Supplements; D005260:Female; D005307:Fertilization in Vitro; D005858:Germany / Q000453:epidemiology; D006801:Humans; D007247:Infertility, Female / Q000188:drug therapy*; D016015:Logistic Models; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons; D014807:Vitamin D / Q000627:therapeutic use*; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications* / Q000453:epidemiology
chemical_list: D014807:Vitamin D
keywords: BMI; Female; Infertility; Season; Vitamin D