Vitamin D concentrations during pregnancy and in cord blood: a systematic review and meta-analysis.

CONTEXT: Effect size estimates for the association between vitamin D concentrations in maternal blood during pregnancy and in cord blood vary widely across studies, but no meta-analysis has been conducted to ascertain this association. OBJECTIVE: The aim of this systematic review was to estimate the pooled effect size for the association between circulating 25-hydroxyvitamin D (25[OH]D) concentrations, a marker of vitamin D status, in maternal blood during pregnancy and in cord blood. DATA SOURCES: The PubMed, Embase, and Web of Science databases were searched from their inception to February 2021. DATA EXTRACTION: Following the application of prespecified inclusion and exclusion criteria, 94 articles were eligible for full-text review, which was conducted by 2 authors independently. A third author was consulted when necessary and consensus reached. In total, 26 articles, which comprised 30 studies and 6212 mother-infant dyads, were included. Methodological quality was assessed using a modified version of the Joanna Briggs Institute's Critical Appraisal Checklist for Studies Reporting Prevalence Data. Correlation coefficient (r) values for the association between maternal serum 25(OH)D concentrations during pregnancy and in cord blood were extracted. DATA ANALYSIS: The r values were pooled using random-effects meta-analyses. Sensitivity and subgroup analyses were performed to investigate sources of heterogeneity. The pooled r for all studies was 0.72 (95%CI, 0.64-0.79), indicating high heterogeneity (I2 = 95%, P < 0.01). After influential and outlier studies were removed, the pooled r for 9 studies was 0.70 (95%CI, 0.66-0.74), which resulted in a substantial reduction in heterogeneity (I2 = 41%, P=0.10). CONCLUSION: The findings support a positive and large correlation between maternal vitamin D concentrations during pregnancy and vitamin D concentrations in cord blood. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration number CRD42021273348.

Comorbidity of ADHD and allergic diseases in early adolescence: The role of parental smoking at home.

A growing body of research suggests an association between attention deficit hyperactivity disorder (ADHD) and allergic disorders, but little work has been done to explore the role of external factors such as parental smoking at home in the development of comorbid ADHD and allergic disorders. This study aimed to examine the association between allergic diseases and ADHD adjusted for exposure to parental smoking at home in early adolescents. We recruited 250 male (41.7%) and 350 female (58.3%) adolescents (mean [SD] age, 13.29 [0.52] years) via chain-referral sampling. Their ADHD symptoms were assessed by the parent proxy-report version of the Chinese Strengths and Weaknesses of Attention-Deficit/Hyperactivity-symptoms and Normal-behaviours (SWAN) rating scale. Data on the participants' history of clinician-diagnosed allergic diseases, family socio-demographics, and parental smoking habit were collected using a parent-completed questionnaire. Regression analyses were performed to examine the associations of interest. The levels of ADHD symptoms were comparable between allergic and non-allergic participants after controlling for child and family demographics and parental smoking at home. Notably, the risk of probable ADHD was particularly high in participants with food allergies (odd ratio = 4.51, p = 0.011) but not in those with allergic rhinitis after adjusting for parental smoking at home. Our findings suggest that second-hand smoke exposure at home is a potential risk factor underlying the link between ADHD and allergic diseases. Current management guidelines should emphasize the importance of early identification and cessation of tobacco smoke exposure for prevention of comorbidity of ADHD and allergic disorders. Clinical Trial Registration (if any): NA.