Threatened miscarriage is clinically defined as the manifestation of positive fetal heart sounds in pregnancies occurring before the 20th week of gestation, concomitant with vaginal bleeding and a closed cervix.<h4>Objectives</h4>The primary aim of this study was to evaluate the association between serum C-reactive protein (CRP) levels and fetal ultrasound findings in the prediction of threatened miscarriage during the first trimester of pregnancy.<h4>Methods</h4>In this prospective case-control study, a total of 100 pregnant women at 7-13 weeks of gestation were enrolled. The gene discussed is CRP; the disease is spontaneous abortion.