Background Studies exploring the relationship between prenatal vitamin D exposure and childhood asthma have yielded conflicting results. Higher vitamin D intake during pregnancy has been shown to lower the risk of childhood wheeze, yet a study of maternal late-pregnancy serum 25-hydroxyvitamin D suggested higher serum concentrations may be associated with increased childhood asthma.
Objective To assess the relationship between mothers' serum 25-hydroxyvitamin D status and asthma and wheeze phenotypes in their children at age 6 years. Also to explore the relationship between maternal 25-hydroxyvitamin D status and objective measures of childhood atopy and lung function.
Methods Serum 25-hydroxyvitamin D was measured at 34 weeks' gestation in the mothers of 860 children born at term. Wheeze was classified as either transient or persistent/late using questionnaire data collated from 6, 12, 24 and 36 months and 6 years. At 6 years spirometry was performed and atopic status was determined by skin prick testing, exhaled nitric oxide was measured in 451 children and bronchial hyperresponsiveness in 216 children.
Results There were no significant associations between maternal late-pregnancy 25-hydroxyvitamin D status and either asthma or wheeze at age 6 years. Maternal vitamin D status was not associated with transient or persistent/late wheeze; no significant association was found between persistent/late wheeze when subdivided according to atopic status. No associations were found with skin sensitisation or lung function.
Conclusions This study provides no evidence that exposure to higher concentrations of 25-hydroxyvitamin D in maternal serum during late pregnancy increases the risk of childhood asthma, wheeze or atopy.
- Asthma epidemiology
- paediatric asthma
- paediatric lung disease
- clinical epidemiology
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Funding This work within the Southampton Women's Survey has been funded by the Medical Research Council, University of Southampton, British Heart Foundation, and the Food Standards Agency (contract no N05071). The research is supported by infrastructure provided by the Southampton NIHR Respiratory Biomedical Research Units and Nutrition, Diet and Lifestyle Biomedical Research Centre. Dr KC Pike was supported by a grant from the British Lung Foundation who commissioned the research.
Competing interests All authors have completed the Unified Competing Interest form at http://www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare that none of the authors have support from any company for the submitted work; KCP, HMI, SMR, JSAL, CC, NCH, KMG and GR have no relationships with companies that might have an interest in the submitted work in the previous 3 years; their spouses, partners or children have no financial relationships that may be relevant to the submitted work; and KCP, HMI, SMR, JSAL, CC, NCH, KMG and GR have no non-financial interests that may be relevant to the submitted work.
Ethics approval Ethics approval was provided by Southampton and South West Hampshire Local Research Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The Southampton Women's Survey is a complex study with ongoing data collection of many of the waves of the study. We encourage data sharing through collaboration, wherever possible, to maximise the use of the study data. In the first instance, enquiries should be made to the MRC Lifecourse Epidemiology Unit Director, Professor Cyrus Cooper on .
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