Title:
An investigation of vitamin D deficiency in pregnant women and their infants in Giresun province located in the Black Sea region of Turkey.

Abstract:
The aim of this study is to investigate vitamin D deficiency and the associated risk factors in pregnant women and their infants in the Black Sea region of Turkey. One hundred and twenty healthy pregnant women in the last trimester and their healthy newborn pairs were observed between June and August 2017 in Giresun province. The serum 25(OH)D3 and calcium levels were measured through the samples collected from maternal and neonatal cord blood. The effects of maternal lifestyle on the maternal vitamin D levels were assessed by multiple regression analysis. The mean concentrations of 25(OH)D3 were found to be 9.54 ± 6.35 ng/mL and 11.16 ± 6.52 ng/mL in the maternal and neonatal cord blood sera, respectively. Vitamin D deficiency (≤20 ng/mL) and severe vitamin D deficiency (≤5 ng/mL) were observed in between 94.2% and 24.2% of mothers and 90% and 10% of infants, respectively. The clothing style, the consumption of milk/dairy products and antenatal multivitamin supplement usage were found as significant factors on the serum vitamin D levels. Even during the Summer months, the vitamin D deficiency in mothers and infants was observed at high rates in the Eastern Black Sea region of Turkey. As a result, it has been concluded that routine maternal serum 25(OH)D3 measurements for clinical follow-up, vitamin D supplementation and regular consumption of dairy products should be recommended. Impact Statement What is already known on this subject? Vitamin D deficiency is a very important risk factor to be considered for maternal and infant health. In a large number of studies, it has been observed that the risk of a vitamin D deficiency in women during their pregnancy was found to be higher, depending on the various strong influences such as the demographic and maternal lifestyles. What the results of this study add? A vitamin D deficiency associated with the demographic and lifestyle factors of pregnant women and their infants was investigated in Giresun province, located in the Eastern Black Sea region of Turkey. The results of this study add that a vitamin D deficiency in the maternal and in the infants may be observed at high rates in regions with mostly rainy weather, even during the Summer months. What the implications are of these findings for clinical practice and/or further research? The vitamin D levels in infants can be determined indirectly by looking at the vitamin D levels in third trimester pregnancies. Furthermore, it is suggested as a non-invasive method to determine vitamin D levels by taking advantage of the maternal level, without measuring the vitamin D levels of infants. Thus, this will be effective to reduce health costs and to prevent the possible diseases affecting the future life of infants. Routine maternal serum 25(OH)D3 measurements for clinical follow-up, vitamin D supplementation and the regular consumption of dairy products should be recommended to pregnant women with risk factors, even in the Summer in the Black Sea Region of Turkey. In addition, further studies are needed to investigate the vitamin D deficiency associated with the demographic and lifestyle factors of pregnant women and their infants, especially for the different locations of Turkey.