Effects of Vitamin D Supplementation During Pregnancy on Birth Size: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.
Plain language summary
Vitamin D deficiency may affect mother and neonatal outcomes, increasing the risk of pregnancy complications, preterm birth, low birth weight (LBW), small for gestational age (SGA), and poor offspring health. This systematic review and meta-analysis evaluates the effects of oral vitamin D supplementation during pregnancy on foetal growth and incidence of LBW and SGA births. 13 randomised controlled trials (RCTs), published between 1980 and 2016, were included in the meta-analysis, including in total 2016 newborns (1184 from mothers in the intervention groups and 832 from controls). Dosages ranged from 200-4000 IU for daily intakes and 35000 IU to 600000 IU for single or intermittent administration. Whilst there was no evidence for publication bias (e.g. an over-reporting of positive outcomes), overall, the quality of the reviewed studies varied from very low (head circumference) to moderate (birth weight, birth length, LBW, and SGA). All studies evaluating the effect of vitamin D supplementation on blood 25-hydroxyvitamin D (OHD) levels showed that intervention significantly increased 25-OHD concentration in both mothers and infants. The meta-analysis showed that vitamin D supplementation significantly increased birth weight and length, independent of dosage and whether vitamin D was administered daily or in single/intermittent high dosages. Head circumference was increased in a non-dose dependent way with daily but not with single/intermittent vitamin D supplementation. Effects on all three parameters were seen when vitamin D was supplemented alone, but not in combination with other nutrients. Both, risk of LBW and SGA, were also significantly reduced with vitamin D supplementation.
During pregnancy, vitamin D supplementation may be a feasible strategy to help prevent low birthweight (LBW) and small for gestational age (SGA) births. However, evidence from randomized controlled trials (RCTs) is inconclusive, probably due to heterogeneity in study design and type of intervention. A systematic literature search in the PubMed-Medline, EMBASE, and Cochrane Central Register of Controlled Trials databases was carried out to evaluate the effects of oral vitamin D supplementation during pregnancy on birthweight, birth length, head circumference, LBW, and SGA. The fixed-effects or random-effects models were used to calculate mean difference (MD), risk ratio (RR), and 95% Confidence Interval (CI). On a total of 13 RCTs, maternal vitamin D supplementation had a positive effect on birthweight (12 RCTs; MD = 103.17 g, 95% CI 62.29⁻144.04 g), length (6 RCTs; MD = 0.22 cm, 95% CI 0.11⁻0.33 cm), and head circumference (6 RCTs; MD:0.19 cm, 95% CI 0.13⁻0.24 cm). In line with these findings, we also demonstrated that maternal vitamin D supplementation reduced the risk of LBW (3 RCTs; RR = 0.40, 95% CI 0.22⁻0.74) and SGA (5 RCTS; RR = 0.69, 95% CI 0.51⁻0.92). The present systematic review and meta-analysis confirmed the well-established effect of maternal vitamin D supplementation on birth size. However, further research is required to better define risks and benefits associated with such interventions and the potential implications for public health.
Effect of park prescriptions with and without group visits to parks on stress reduction in low-income parents: SHINE randomized trial.
PloS one. 2018;(2):e0192921
INTRODUCTION Exposure to nature may reduce stress in low-income parents. This prospective randomized trial compares the effect of a physician's counseling about nature with or without facilitated group outings on stress and other outcomes among low-income parents. MATERIALS AND METHODS Parents of patients aged 4-18 years at a clinic serving low-income families were randomized to a supported park prescription versus independent park prescription in a 2:1 ratio. Parents in both groups received physician counseling about nature, maps of local parks, a journal, and pedometer. The supported group received additional phone and text reminders to attend three weekly family nature outings with free transportation, food, and programming. Outcomes measured in parents at baseline, one month and three months post-enrollment included: stress (using the 40-point Perceived Stress Scale [PSS10]); park visits per week (self-report and journaling); loneliness (modified UCLA-Loneliness Scale); physical activity (self-report, journaling, pedometry); physiologic stress (salivary cortisol); and nature affinity (validated scale). RESULTS We enrolled 78 parents, 50 in the supported and 28 in the independent group. One-month follow-up was available for 60 (77%) participants and three-month follow up for 65 (83%). Overall stress decreased by 1.71 points (95% CI, -3.15, -0.26). The improvement in stress did not differ significantly by group assignment, although the independent group had more park visits per week (mean difference 1.75; 95% CI [0.46, 3.04], p = 0.0085). In multivariable analysis, each unit increase in park visits per week was associated with a significant and incremental decrease in stress (change in PSS10-0.53; 95% CI [-0.89, -0.16]; p = 0.005) at three months. CONCLUSION While we were unable to demonstrate the additional benefit of group park visits, we observed an overall decrease in parental stress both overall and as a function of numbers of park visits per week. Paradoxically the park prescription without group park visits led to a greater increase in weekly park visits than the group visits. To understand the benefits of this intervention, larger trials are needed. TRIAL REGISTRATION ClinicalTrials.gov NCT02623855.