Background: Subchorionic hemorrhage (SCH), also referred to as subchorionic hematoma, is the most common sonographic abnormality associated with first-trimester vaginal bleeding. It occurs between 6 and 13 weeks of gestation and is reported in approximately 11% of pregnancies. SCH is characterized by bleeding between the chorionic membrane and the uterine wall. Aim: This study aimed to evaluate the association between the volume of first-trimester subchorionic hematoma and the risk of spontaneous miscarriage. Methods: A cross-sectional study was conducted involving 53 pregnant women in their first trimester, aged 18–35 years, who attended the obstetric clinic at Al-Diwaniyah Maternity and Children Teaching Hospital between May and November 2022. Women with a viable intrauterine pregnancy, gestational age between 6 and 13 weeks, and an ultrasound-confirmed diagnosis of subchorionic hematoma were included in the study. Fetal viability was assessed by ultrasonography. Hematomas were categorized according to their volume. Data were collected and analyzed using Statistical Package for the Social Sciences (SPSS) version 23. Results: The mean age of the participants was 28.3 ± 6.4 years (range: 18–35 years). Participants were stratified into three age groups. The mean hematoma volumes were 9.4 ± 2.5 cm³ for small hematomas, 16.3 ± 1.2 cm³ for medium hematomas, 22.7 ± 3.4 cm³ for large hematomas, and 37.2 ± 9.4 cm³ for very large hematomas. Women who experienced spontaneous abortion had significantly larger hematoma volumes compared with those who maintained their pregnancies (p < 0.05). The mean gestational age was 8.9 ± 1.3 weeks among women with small hematomas and 10.2 ± 1.9 weeks among those with very large hematomas. Conclusion: An Increased Volume of Subchorionic Hematoma during the First Trimester is Significantly Associated with a Higher Risk of Spontaneous Abortion.