Introduction:
Vitamin D deficiency or insufficiency is thought to be common among pregnant women. Recently, a special attention has been paid to gestational hypovitaminosis D in relation to pregnancy outcomes. There is little information on vitamin D intake in pregnancy and lactation and few studies on clinical outcomes. Vitamin D supplementation during pregnancy has been suggested as an intervention to protect against adverse gestational outcomes.

Objective:
The aim of this study is to determine the necessary vitamin D supplementation in a cohort of Greek pregnant women. The main goals of this study are: a) to analyze and correlate data of pregnant women with different therapeutic protocols for vitamin D supplementation during pregnancy and relation to vitamin D insufficiency or deficiency of the newborn.

Material and Methods:
All pregnant women from a private clinic of a maternity hospital in Athens were randomized and included in the study. A single blind randomized design was used in order to define three groups of pregnant women who received different vitamin D3 supplementation after the 12th week of pregnancy (Group A<8400 IU per week; Group B<12800 IU per week; Group C>16800 IU per week). Maternal vitamin D3(OH-VitD3) levels were recorded on the 3rd month of gestation and the 1st postpartum day. Newborns’ vitamin levels (OH-VitD3) were measured on the 3rd day of their life.

Results:
In total 192 pregnant women and 194 newborns were involved in the study. Newborns absorb Vitamin D3 from their mother. There is a significant proportion of pregnant women who have vitamin D deficiency or insufficiency both on the 3rd month of gestation (91%) and on the delivery date (80%). Only 15% of newborns demonstrated low vitamin D levels at birth. Vitamin D supplementation with a dose of 16800 iu weekly from the 3rd month of pregnancy seems to have a significant effect on fetal vitamin D levels, resulting to no infant with vitamin D deficiency (less than 15ng/ml). In our survey there is no indication of adverse effect of Vitamin D on newborn’s weight or premature labor. Premature labor is not associated with higher maternal levels of vitamin D.

Conclusions:
Vitamin D supplementation during pregnancy is safe and provides an efficient therapeutic modality to prevent maternal and neonatal vitamin D deficiency or insufficiency.