The White Blood Cell Count in Laboring Women at Term Is Associated with Neonatal Macrosomia.

Background: Fetal weight estimation at term is a challenging clinical task.

Objectives: To evaluate the association between peripheral white blood cell (WBC) count of the laboring women and neonatal birth weight (BW) for term uncomplicated pregnancies.

Methods: We conducted a single-center, retrospective cohort study (2006-2021) of women admitted in the first stage of labor or planned cesarean delivery. Complete blood counts were collected at admission. BW groups were categorized by weight (grams): < 2500 (group A), 2500-3499 (group B), 3500-4000 (group C), and > 4000 (group D). Two study periods were used to evaluate the association between WBC count and neonatal BW.

Results: There were a total of 98,632 deliveries. The dataset analyses showed a lower WBC count that was significantly and linearly associated with a higher BW; P for trend < 0.001 for women in labor. The most significant association was noted for the > 4000-gram newborns; adjusted odds ratio 0.97, 95% confidence interval 0.96-0.98; P < 0.001; adjusted for hemoglobin level, gestational age, and fetal sex. The 2018-2021 dataset analyses revealed WBC as an independent predictor of macrosomia with a significant incremental predictive value (P < 0.0001). The negative predictive value of the WBC count for macrosomia was significantly high, 93.85% for a threshold of WBC < 10.25 × 103/µl.

Conclusions: WBC count should be considered to support the in-labor fetal weight estimation, especially valuable for the macrosomic fetus.