Association of Sunlight Exposure and Consumption of Vitamin D-Rich Foods During Pregnancy with Adverse Birth Outcomes in an African Population

Effect of maternal vitamin D status on risk of adverse birth outcomes: a systematic review and dose-response meta-analysis of observational studies

PURPOSE

Accumulating evidence suggests that vitamin D deficiency increases the risk of adverse perinatal outcomes. However, the dose-response relationship between maternal vitamin D status and adverse birth outcomes remains unclear. Focusing on prospective observational studies, we aimed to explore the dose-response relationship of vitamin D status with the risk of low birth weight (LBW), macrosomia (MA), preterm birth (PTB), small for gestational age (SGA), and intrauterine growth restriction (IUGR).

METHODS

Databases including PubMed, Embase, Scopus, and Web of Science were used up to 19 January 2021 to search for observational studies that fulfilled criteria as follows: cohort studies, case-cohort studies, or nested case-control studies. Random-effects models were used to pool relative risks (RRs) and 95% confidence intervals (CIs) in the observational studies.

RESULTS

A total of 72 publications were included in this systematic review and 71 in the meta-analysis. Maternal 25-hydroxyvitamin D (25(OH)D) concentrations were inversely associated with the risk of LBW (RR: 0.65; 95% CI 0.48-0.86), PTB (RR: 0.67; 95% CI 0.57-0.79), and SGA (RR: 0.61; 95% CI 0.49-0.76) in the highest versus lowest meta-analysis, but not associated with MA and IUGR. Linear dose-response analysis showed that each 25 nmol/L increase in 25(OH)D was associated with a 6% and 10% reduction in the risk of PTB (RR: 0.94; 95% CI 0.90-0.98) and SGA (RR: 0.90; 95% CI 0.84-0.97), respectively.

CONCLUSION

Our study suggests that a sufficient vitamin D status during pregnancy is protective against the risk of LBW, PTB, and SGA.

Vitamin D Levels in Mother-Baby Pairs: A Cross-Sectional Prospective Study in a Rwandan Tertiary Hospital

BACKGROUND

Exposure to the sunlight contributes largely to the production of vitamin D. However, vitamin D deficiency is a reality in tropical countries, despite enjoying enough sunlight, especially bearing women in their last trimester whose foetuses exclusively depend on their reserves. This work aimed at demonstrating the state of vitamin D in mother-baby pairs and associated factors in one of the University Hospitals in Rwanda.

METHODS

This cross-sectional prospective study was performed on mother-baby pairs at Kigali University Hospital. Mother's serum 25-hydroxyvitamin D levels were considered as outcomes compared with demographic, clinical and biological markers. Correlation analysis was conducted in order to assess the association between serum 25-hydroxyvitamin D levels for the couple mothers-babies.

RESULTS

Approximately 38% of women and 65% of neonates had deficiency in 25-hydroxyvitamin D (<20 ng/ml). The use of a vitamin D rich diet within 24 h recall (p < 0.01) or 1 week recall (p < 0.001) before delivery was associated with appropriate vitamin D levels in mothers. Interestingly, a strong positive correlation was found between maternal and neonatal serum 25-hydroxyvitamin D levels (r = 0.760).

CONCLUSIONS

There was a high rate of vitamin D deficiency in mothers and their babies. Babies born from women with deficiency were likely to develop low levels of vitamin D. This stresses on the need to strengthen the interventions for preventing vitamin D deficiency in the couple mothers-babies such as supplement in vitamin D before and after delivery, improving the quality of meals and regular contact with sunlight.