Assessment of CA-125 and progesterone serum levels as markers for pregnancy loss in first trimester threatened abortion

Background: Threatened abortion is one of the most frequent complications during early pregnancy and carries a significant risk of miscarriage. Identifying reliable biomarkers such as CA-125 and progesterone may improve early risk stratification and management. Objective: To evaluate the clinical utility of serum CA-125 and progesterone levels in predicting pregnancy outcomes in women presenting with threatened abortion and to examine their correlation with ultrasonographic findings and prior obstetric history. Methods: A prospective case-control study was conducted at Tikrit Teaching Hospital from October 1, 2024, to June 30, 2025, involving 90 pregnant women between 6-12 weeks of gestation. Participants were divided into two groups: 45 women with threatened abortion (cases) and 45 with healthy first-trimester pregnancies (controls). Serum CA-125 and progesterone levels were analyzed, and all participants underwent detailed transvaginal ultrasonography. Outcomes were followed until the end of the first trimester. Results: Women with threatened abortion had significantly higher CA-125 levels (50.23±28.14 IU/mL vs. 29.56±16.87 IU/mL, P=0.031) and lower progesterone levels (35.11±18.35 ng/mL vs. 42.89±20.22 ng/mL, P=0.048) compared to controls. Among the threatened abortion group, those who experienced miscarriage had markedly higher CA-125 levels (68.14±20.62 IU/mL) and lower progesterone (18.79±9.33 ng/mL) than those who continued pregnancy (P=0.012 and P=0.004, respectively). Additionally, 84.6% of women who aborted had CA-125 > 42 IU/mL and 84.6% had progesterone ≤ 28 ng/mL, compared to only 18.7% and 15.6% in the continued pregnancy group (P=0.001 for both). Significant associations were observed between adverse outcomes and poor ultrasound parameters including lower fetal heart rate (145.1±7.9 bpm vs. 160.3±8.2 bpm, P=0.002), reduced crown-rump length (22.4±4.2 mm vs. 28.7±3.5 mm, P=0.005), smaller gestational sac diameter (28.5±5.0 mm vs. 32.9±4.1 mm, P=0.018), and shorter cervical length (29.6±3.3 mm vs. 34.2±2.6 mm, P=0.004). Prior abortion history was also strongly linked to miscarriage: 76.9% of women who miscarried had one or more previous abortions (p 42.0 IU/mL. Progesterone had an AUC of 0.86, sensitivity of 75.7%, and specificity of 94.2% at a cut-off < 28.0 ng/mL. Conclusion: Serum CA-125 and progesterone are valuable non-invasive biomarkers for predicting miscarriage in cases of threatened abortion. When combined with ultrasonographic findings and prior obstetric history, these markers provide a robust model for early identification of high-risk pregnancies, enabling timely intervention and improved antenatal care.