Vitamin D deficiency may lead to decreased egg quality, decreased endometrial tolerance, predispose to miscarriage, and increase the risk of pre-eclampsia and gestational diabetes during pregnancy. Vitamin D is a fat-soluble vitamin that promotes skin cell growth, immune function, and new bone production and calcification. Studies have shown that vitamin D deficiency may lead to decreased egg quality, decreased endometrial tolerance, miscarriage, and polycystic ovary syndrome. In addition, vitamin D is important for maintaining a normal pregnancy, and vitamin D deficiency in pregnant women can lead to fetal bone development and tooth enamel formation. It is very important to maintain vitamin D in the normal range during pregnancy, and if you are deficient, it is best to take supplements under the guidance of your doctor, get plenty of sunshine, have a balanced diet, and eat plenty of vitamin D-rich foods.