Pregnancies complicated by preeclampsia (PE) are characterised by an enhanced maternal and fetal inflammatory response with increased numbers of leukocytes in maternal peripheral blood. The impact of PE on newborn umbilical cord blood cell (UCBC) populations however, has been scarcely studied. We hypothesise that PE deranges fetal haematopoiesis and subsequently UCBC populations. Therefore, the objective of this study was to investigate newborn umbilical cord blood cell populations in early- (EOPE) and late-onset PE (LOPE). A secondary cohort analysis in The Rotterdam Periconceptional Cohort was conducted comprising 23 PE cases, including 11 EOPE and 12 LOPE, and 195 controls, including 153 uncomplicated and 23 fetal growth restriction- and 19 preterm birth complicated controls. UCBC counts and differentials were quantified by flow cytometry and analysed as main outcome measures. Multivariable regression analysis revealed associations of EOPE with decreased leucocyte- (monocytes, neutrophils, eosinophils, immature granulocytes) and thrombocyte counts and increased NRBC counts (all p < 0.05). EOPE remained associated with neutrophil- (β-0.92, 95%CI -1.27,-0.57, p < 0.001) and NRBC counts (β1.11, 95%CI 0.27,1.95, p = 0.010) after adjustment for gestational age and birth weight. LOPE did not reveal any significant association. We conclude that derangements of fetal haematopoiesis, in particular of neutrophil- and NRBC counts, are associated with EOPE only, with a potential impact for future health of the offspring. This heterogeneity in UCBC should be considered as confounder in epigenetic association studies examining EOPE.