en Obstetrics & Gynicology Obstetrics & Gynicology Original Article Original Article <span style="font-size:14px;"><span style="font-family:Times New Roman;"><span style="line-height:14pt"><b><i><span style="color:blue">Background</span></i></b><i><span style="color:blue">:</span></i>The objective of this study was to compare the levels of vitamin D in non-pregnant women with a history of recurrent pregnancy loss (RPL) who were seropositive or seronegative for autoantibodies (autoAbs).</span><br> <span style="line-height:14pt"><b><i><span style="color:blue">Methods: </span></i></b>The study examined 58 RPL patients with autoAbs (ANA, anti-TPO, or APAs), 34 RPL patients without autoAbs, and 58 healthy women with prior successful pregnancies and without autoantibodies. The levels of 25 (OH) D were measured using the sandwich ELISA technique.<span style="font-size:10.0pt"></span></span><br> <span style="line-height:14pt"><b><i><span style="color:blue">Results:</span></i></b>Our results showed insufficient serum 25(OH) D levels in study groups, with significantly lower levels observed in RPL patients with or without autoAbs compared to healthy women (P=0.0006).&nbsp; In addition, RPL patients with autoAbs had significantly lower 25(OH) D levels compared to RPL patients without autoAbs. We also found that serum levels of 25(OH) D in RPL patients with autoAbs were significantly lower than in RPL patients without autoAbs (20.51 &plusmn; 1.15 ng/ml Vs. 23.69 &plusmn; 0.74 ng/ml, <i>P</i>=0.0356). Further analysis indicated that RPL patients who were positive for ANA, and APAs, except anti-TPO, had significantly lower than 25(OH)D serum levels than RPL patients without autoAbs. </span><br> <span style="line-height:14pt"><b><i><span style="color:blue">Conclusion</span></i></b><i><span style="color:blue">: </span></i>These findings suggest that RPL patients, especially those with APAs or ANA, have lower vitamin D levels compared to healthy women. This may indicate a link between maternal immune dysregulation due to vitamin D deficiency and the presence of autoantibodies in RPL. </span></span></span><br> &nbsp; Vitamin D, Recurrent pregnancy loss, antinuclear antibody, Antiphospholipid antibody, Anti-thyroid peroxidase. 266 272 http://caspjim.com/browse.php?a_code=A-10-3040-1&slc_lang=en&sid=1 Tooba Farazmand toobafarazmand@gmail.com 100319475328460047723 100319475328460047723 No Department of Gynecology, School of Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran Raheleh Rahbarian ra_rahbarian@yahoo.com 100319475328460047724 100319475328460047724 No Department of Biology, Payame noor university, Tehran, Iran Mitra Jalali m.jalali.231@gmail.com 100319475328460047725 100319475328460047725 No Department of Biology, Payame noor university, Tehran, Iran Amirali Ghahremani amirali.ghahremani@yahoo.com 100319475328460047726 100319475328460047726 No Department of Internal Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran. Abdollah Razi abdolahrazi@gmail.com 100319475328460047727 100319475328460047727 No Department of Urology, Imam Ali Hospital, North Khorasan University of Medical Sciences, Bojnurd Iran Hasan Namdar Ahmadabad namdar360@gmail.com 100319475328460047728 100319475328460047728 Yes Vector-borne Diseases Research Center, North Khorasan University of Medical Sciences, Bojnurd, Iran