**4. Maternal vitamin D status and adverse pregnancy outcomes**

Numerous studies have reported pleiotropic role of vitamin D in pregnancy. Maternal Hypovitaminosis D during pregnancy is related to pregnancy related disorders. Complications caused by low serum measurement of 25(OH)D include gestational hypertension (GHT), PET, gestational diabetes mellitus (GDM), timing and mode of delivery, postpartum depression or anxiety, bacterial vaginosis, and other outcomes such as anemia and lipid disorders, which are discussed in this section.

It should be noted that, there is not enough evidence to support a recommendation for screening all pregnant women for vitamin D deficiency but must be at least 20 ng/ml (50 nmol/L) for bone health [35]. Although some experts suggest vitamin D serum level of at least 32 ng/ml (80 nmol/L) for optimal state in pregnancy [36], some adverse effects have been reported at levels exceeding 70 nmol/L [37]. Consequently, due to the lack of standardized measurement procedures, there is no consensus on the optimal vitamin D status during pregnancy.
