Infants born to mothers with preeclampsia often develop neutropenia and thrombocytopenia after birth. However, the risk of sepsis associated with preeclampsia and neutropenia remains unknown. Objective: investigate the changes in the complete blood count and risk of culture proven sepsis in infants born to mothers with preeclampsia. Methods: case control study of infants born <1500g at a single level III NICU from 7/93-7/97. Infants born to mothers with preeclampsia (n=89) were compared to a control group of infants born to mothers without preeclampsia (n=416). Values from complete blood counts obtained on admission and day of life 1-3, as well as the rate of culture proven sepsis, were compared between groups. Data were analyzed using Student's t-test, Chi-square, repeated measures ANOVA with post hoc testing, and multivariate logistic regression. Results: Infants in the preeclampsia group were of advanced gest. age (29.8 ± 2.9 vs 28.0 ± 2.8 weeks, p<.001), were less likely to have received prenatal steroids (45 vs 58%, p=.02), have mothers with chorioamnionitis (0 vs 9%, p=.004), or prolonged rupture of membranes (1 vs 25%, p<.001) compared to the control group. Infants in the preeclampsia group had a lower absolute neutrophil count (ANC) on admission (2.9±2.5 vs 5.7±5.7 mm3, p<.01), day 1 (5.0±3.6 vs 9.6±8.8, p<.01), day 2 (4.0±2.7 vs 8.6±9.6, p<.01), and day 3 (3.1±2.1 vs 7.1 ± 8.3, p<.01) compared to controls. The preeclampsia group also had a statistically lower total white blood cell count (WBC) and platelet count on admission and on each day from day 1-3 compared to the control group. There was no difference in the rate of culture proven sepsis between the groups (14% preeclampsia vs 18% control, p=.3). Preeclampsia (odds ratio:1.8, 95% CI.6-5.4,p=.3), ANC or WBC on admission or at any time in the first 72 hours of life was not associated with increased odds of culture proven sepsis during the infant's hospital course after controlling for confounding variables. Conclusions: In our population, preeclampsia is associated with a decrease in WBC, ANC and platelet count that persists during the 1st 72 hours of life. However, this decrease in WBC and ANC is not associated with an increased risk of culture proven sepsis. We speculate that therapies designed for preeclampsia associated neutropenia to prevent sepsis would be ineffective.