Vitamin D deficiency and pregnancy disorders
Vitamin D deficiency (VDD) is a global health care issue, with billion carrying deficiency or insufficiency around the world. This hormone plays a kaleidoscope of important roles throughout pregnancy, so that maintenance of an adequate vitamin D status is essential in this setting. Several studies, which have investigated vitamin D status in different populations of pregnant women, have convincingly reported high prevalence of vitamin D insufficiency, consistently higher than 50%. Although VDD developing during pregnancy has been associated with some adverse maternal and pregnancy outcomes, especially gestational diabetes mellitus (GDM) and preeclampsia (PE), the risk estimated are considerably heterogeneous, which makes it challenging to define operative recommendations. The mean differences in serum 25-hydroxy- cholecalciferol [25(OH)D] between GDM and non-GDM pregnant women varies between −4.93 and −7.36 nmol/L, whilst that between pre-eclamptic and non-pre-eclamptic pregnant women is even wider, being comprised between −3.86 and −14.53 nmol/L. It is hence still unclear whether assessment of vitamin D during pregnancy shall be recommended, as well as which dose of vitamin D shall be administered in pregnant women with VDD. Further studies shall be planned, which will need to be based on reliable quantification techniques [preferably liquid chromatography tandem mass spectrometry (LC-MS/MS)-based methods], but will also need to reduce the impact of many confounding factors such as ethnicity, sunlight exposure and sampling time.