Ferdous, S.; Hussain, F.; Hayee, S.; Akhtar, N.; Khanam, S.; Begum, K.; Sultana, A. The Effect of the Maternal Vitamin D Level on the Risk of Spontaneous Pregnancy Loss in the First Trimester. Int J Reprod Contracept Obstet Gynecol 2021, 10, 2215-2220.