Objective: Invasive group A streptococcal (GAS) infections during pregnancy are uncommon, and, thus, their early diagnosis remains challenging. The present study was performed to assess fibrin/fibrinogen degradation product (FDP) and D-dimer levels in pregnant women with invasive GAS infections and establish whether they contribute to a diagnosis. Materials and Methods: Laboratory data, including FDP and D-dimer levels, measured between fulmination and just before delivery in 46 cases, consisting of 45 previously published cases and the present case, were examined. Results: Fetal/neonatal and maternal mortality rates were 61 and 28%, respectively. Laboratory data obtained from 24 cases just before delivery were as follows: white blood cell count ≥ 12,000/µL, 46% of cases; platelet count ≤ 100,000/µL, 55% of cases, and C-reactive protein (CRP) level ≥ 10 mg/dL, 40% of cases. These variables showed no sensitivity for the diagnosis of invasive GAS infections. However, 100% of cases were positive for FDP (≥ 10 µg/dL) and D-dimer (≥ 2 µg/dL), the levels of which were extremely high in many cases. Conclusion: FDP and D-dimer levels may contribute to the diagnosis of invasive GAS infections during pregnancy.