Vitamin D supplementation in pregnant or breastfeeding women or young children for preventing asthma

Evidence supporting a protective effect of vitamin D supplementation in early life, including the prenatal period, on childhood asthma is limited. Moderate-certainty evidence suggests that high-dose vitamin D in pregnancy likely helps prevent childhood wheeze. Evidence for the effects of vitamin D in early childhood on asthma or wheeze is less certain. Additional high-quality studies, especially in infants and children, are needed to establish with any certainty the effects of vitamin D supplementation on childhood asthma and associated factors.