Reference Intervals of Hematological Parameters Among Healthy Pregnant Women in Eastern Sudan: A Prospective Longitudinal Cohort Study.

BACKGROUND

Pregnancy induces maternal hematological adaptations. Because these shifts are influenced by environmental, nutritional, and ethno-geographic variations, relying on international adult reference intervals (RIs) may increase the risk of diagnostic misclassification. Given the scarcity of context-specific reference intervals in Sudan, this study aimed to establish the localized, trimester-specific complete blood count (CBC) RIs for healthy pregnant women in Eastern Sudan.

METHODS

This hospital-based longitudinal cohort study included apparently healthy pregnant women during their first trimester and followed up till the third trimester at Gadarif Maternity Hospital. CBC parameters were analyzed using a Sysmex KX-21 automated analyzer. Following CLSI guidelines, trimester-specific 95% RIs were determined non-parametrically by calculating the central 2.5th and 97.5th percentiles. Cross-trimester variations were analyzed using the Friedman test.

RESULTS

Of the 120 included, total white blood cell (WBC) counts increased significantly from the first trimester median of 7.6 ×109/L (95% RI: 4.0-11.8 ×109/L) to a second trimester peak of 8.5×109/L (95% RI: 4.7-13.1109/L; p < 0.001). Conversely, red blood cell (RBC) counts decreased across gestation (p < 0.001). Hemoglobin and hematocrit levels reached the lowest observed median in the second trimester (10.7 g/dL, 95% RI: 9.1-12.8; 34.7%, 95% RI: 30.2-39.5%), followed by a modest but significant third-trimester recovery (p = 0.008 and p = 0.006). Both MCV and MCH exhibited progressive, significant cross-trimester increases (p < 0.001), while MCHC remained uniform (p = 0.373). Platelet counts demonstrated a linear decline to a third-trimester nadir of 230.5×109/L (95% RI: 128.4-356.9×109/L; p < 0.001), while platelet distribution width (PDW) expanded progressively (p < 0.001).

CONCLUSION

This study showed that CBC parameters vary significantly across trimesters and differ from international baselines. The second-trimester hemoglobin lower boundary of 9.1g/dL and late-pregnancy gestational thrombocytopenia need further validation in larger and more diverse populations before routine clinical use.