Aim: Immature granulocytes, an indicator of increased myeloid cell production, are associated with infection or systemic inflammation. Data on the use of immature granulocyte levels as a biochemical marker in infection and inflammatory conditions have been reported. In our study, we aimed to determine the reference intervals of immature granulocyte levels according to the gestational period.

Material and Methods: Immature granulocyte (delta neutrophil) counts and percentages were obtained by retrospective analysis of complete blood count results obtained from 1289 healthy pregnant women. Data were analyzed with SPSS 23.0 software. Data were grouped according to gestational weeks by K-clustering analysis. Nonparametric method was used according to CLSI standard C28-A3. The 2.5-97.5% percentile values of the groups with 90% confidence intervals were used as reference intervals.

Results: Immature granulocyte reference interval value is 0.01-0.12 (0.11-0.13) 109/L for 4-25th gestational week and 0.02 (0.02-0.03)-0.21 (0.20-0.22) 109/L for 26-40th gestational week. The reference interval values of immature granulocyte % ratio was 0.2-0.9% (0.8-0.9) for 4-25th gestational week and 0.3-1.6% (1.5-1.7) for 26-40th gestational week.

Conclusions: When compared with the immature granulocyte reference intervals of the adult group, immature granulocyte values and ratios were found to be increased in the healthy pregnant population. We think that our IG reference interval data during pregnancy may help gynaecologists to make clinical decisions in the follow-up of pregnant women.