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Maternal serum concentrations of vitamin D in pregnancy and preterm birth : a case-control study in Southern Sweden

Olstrup, Henrik LU ; Rylander, Lars LU orcid ; Lindh, Christian LU orcid ; Malm, Gunilla LU and Vilhelmsson, Andreas LU orcid (2025) In European Journal of Nutrition 64(5).
Abstract

Purpose: The purpose of this case-control study was to investigate the associations between maternal serum concentrations of vitamin D early in pregnancy and the occurrence of preterm birth. Methods: The study included 269 women (cases) whose children were born preterm (< 37 gestational weeks [gw]) and 332 women (controls) whose children were born term (≥ 37 gw). Among the cases, 59 were extreme preterm (< 28 gw), 74 severe preterm (28‒32 gw), and 136 late preterm (33‒36 gw). All women gave birth in Scania, the most Southern County of Sweden. Concentrations of 25-hydroxyvitamin D3 (vitamin D) in maternal serum collected early in pregnancy were analyzed using liquid chromatography-tandem-mass-spectrometry (LC/MS/MS). The... (More)

Purpose: The purpose of this case-control study was to investigate the associations between maternal serum concentrations of vitamin D early in pregnancy and the occurrence of preterm birth. Methods: The study included 269 women (cases) whose children were born preterm (< 37 gestational weeks [gw]) and 332 women (controls) whose children were born term (≥ 37 gw). Among the cases, 59 were extreme preterm (< 28 gw), 74 severe preterm (28‒32 gw), and 136 late preterm (33‒36 gw). All women gave birth in Scania, the most Southern County of Sweden. Concentrations of 25-hydroxyvitamin D3 (vitamin D) in maternal serum collected early in pregnancy were analyzed using liquid chromatography-tandem-mass-spectrometry (LC/MS/MS). The serum concentrations of vitamin D were trichotomized based on the distributions among the controls (≤ 44.9; 45.0‒68.8; and ≥ 68.9 nmol/L) as well as dichotomized at a predefined cut-off (< 50 and ≥ 50 nmol/L). Logistic regression was used to estimate the associations between vitamin D and preterm births, partly when all cases were included in the analyses, and partly when the three different case groups were included separately. The category with the highest vitamin D concentration was used as a reference in the regression analyzes. The analyses were performed without as well as with adjustments for potential confounders. Results: When the category with the lowest vitamin D concentrations were compared with the reference category in the analyses where the vitamin D concentrations were trichotomized, no statistically significant associations were observed. However, among the extreme preterm an adjusted odds ratio of 1.93 (95% confidence interval 0.83‒4.48) was observed. The patterns were similar when 50 nmol/L was used as the cut-off. Conclusion: Although all comparisons gave adjusted odds ratios in the direction that low maternal vitamin D concentrations early in pregnancy increase the risk of preterm birth, none of these were statistically significant. Accordingly, the present study gives no to very weak support for an association.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Extreme preterm, Late preterm, Logistic regression, Scania, Severe preterm, Vitamin D
in
European Journal of Nutrition
volume
64
issue
5
article number
198
publisher
Springer
external identifiers
  • pmid:40448825
  • scopus:105007240430
ISSN
1436-6207
DOI
10.1007/s00394-025-03716-8
language
English
LU publication?
yes
additional info
Publisher Copyright: © The Author(s) 2025.
id
e356fede-fb26-4203-a089-fbdf050c5a78
date added to LUP
2025-06-12 10:02:30
date last changed
2025-07-10 13:00:16
@article{e356fede-fb26-4203-a089-fbdf050c5a78,
  abstract     = {{<p>Purpose: The purpose of this case-control study was to investigate the associations between maternal serum concentrations of vitamin D early in pregnancy and the occurrence of preterm birth. Methods: The study included 269 women (cases) whose children were born preterm (&lt; 37 gestational weeks [gw]) and 332 women (controls) whose children were born term (≥ 37 gw). Among the cases, 59 were extreme preterm (&lt; 28 gw), 74 severe preterm (28‒32 gw), and 136 late preterm (33‒36 gw). All women gave birth in Scania, the most Southern County of Sweden. Concentrations of 25-hydroxyvitamin D<sub>3</sub> (vitamin D) in maternal serum collected early in pregnancy were analyzed using liquid chromatography-tandem-mass-spectrometry (LC/MS/MS). The serum concentrations of vitamin D were trichotomized based on the distributions among the controls (≤ 44.9; 45.0‒68.8; and ≥ 68.9 nmol/L) as well as dichotomized at a predefined cut-off (&lt; 50 and ≥ 50 nmol/L). Logistic regression was used to estimate the associations between vitamin D and preterm births, partly when all cases were included in the analyses, and partly when the three different case groups were included separately. The category with the highest vitamin D concentration was used as a reference in the regression analyzes. The analyses were performed without as well as with adjustments for potential confounders. Results: When the category with the lowest vitamin D concentrations were compared with the reference category in the analyses where the vitamin D concentrations were trichotomized, no statistically significant associations were observed. However, among the extreme preterm an adjusted odds ratio of 1.93 (95% confidence interval 0.83‒4.48) was observed. The patterns were similar when 50 nmol/L was used as the cut-off. Conclusion: Although all comparisons gave adjusted odds ratios in the direction that low maternal vitamin D concentrations early in pregnancy increase the risk of preterm birth, none of these were statistically significant. Accordingly, the present study gives no to very weak support for an association.</p>}},
  author       = {{Olstrup, Henrik and Rylander, Lars and Lindh, Christian and Malm, Gunilla and Vilhelmsson, Andreas}},
  issn         = {{1436-6207}},
  keywords     = {{Extreme preterm; Late preterm; Logistic regression; Scania; Severe preterm; Vitamin D}},
  language     = {{eng}},
  number       = {{5}},
  publisher    = {{Springer}},
  series       = {{European Journal of Nutrition}},
  title        = {{Maternal serum concentrations of vitamin D in pregnancy and preterm birth : a case-control study in Southern Sweden}},
  url          = {{http://dx.doi.org/10.1007/s00394-025-03716-8}},
  doi          = {{10.1007/s00394-025-03716-8}},
  volume       = {{64}},
  year         = {{2025}},
}