Reduced peripheral natural killer cell counts may be a predictive marker for cesarean scar pregnancy.

Cesarean scar pregnancy (CSP), a condition characterised by inflammation, occurs in 0.2% of women with a history of cesarean section(s), and is clinically categorised by type 1 and type 2 according to the ultrasound findings. Recent studies reported that systemic inflammation indices derived from routine whole-blood tests may serve as additional clinical predictive markers for early CSP detection, with lymphocyte counts showing a reduction. However, the specific lymphocyte populations contributing to this reduction remain unclear. This study included 72 women diagnosed with CSP and 50 gestation-matched controls. The subsets of peripheral lymphocytes, including CD45 lymphocytes/monocytes, CD3 T cells, CD4 T helper cells, CD8 cytotoxic T cells, CD19 B cells, total NK cells and NKT-like cells, were measured. We found a significant reduction in peripheral total NK cells and CD8 cytotoxic T cells in CSP women compared to controls. However, there were no differences in peripheral immune cell profiles between type 1 and type 2 CSP. Using total NK cell counts with a cut-off value of 210/µl, the area under the curve (AUC) was 0.698, with a sensitivity of 64%. Our findings suggest that the reduction in peripheral total NK cells and CD8 T cytotoxic cells may play a role in the development of CSP. Additionally, peripheral total NK cell counts, derived from routine whole-blood tests, could serve as a predictive marker for early CSP diagnosis.