Vitamin D for the prevention of miscarriage and spontaneous preterm birth

Pregnancy represents a dynamic period with physical and physiological changes in both the mother and the developing fetus. Vitamin D was shown to exert many physiological activities during the very early stages of gestation in perfect synchrony with progesterone. Both the molecules mutually help and reinforce the activity exerted by each one. Vitamin D contributes to prepare the endometrium to be receptive and supports the implantation process and the course of pregnancy through similar pathways to those used by progesterone, giving rise to a significant synergy of action. It is increasingly evident that vitamin D gives an essential support from the luteal phase onwards exerting an important role in the establishment and maintenance of pregnancy through its immunomodulatory action and its effects on inflammation within the placenta, preventing miscarriage and preterm birth (PTB). Thus, it is important to guarantee the appropriate levels of vitamin D before placentation (and trophoblast invasion); however further research is needed to decipher vitamin D requirements of pregnant women and the optimal timing of supplementation, taking into account a variety of lifestyles, body types and baseline vitamin D status. Determining the role of vitamin D in non-classical, immune pathways continues to be a challenge that once answered will substantiate recommendations and public health policies.