To determine predictive factors for neonatal thrombocytopenia in deliveries with immune thrombocytopenia (ITP), we conducted a retrospective study at a tertiary hospital between 1997 and 2013. During this period, 30 women with ITP delivered 44 children. Neonatal thrombocytopenia (<100 × 10(9)/L) at birth was observed in seven neonates; four of these cases were severe (<50 × 10(9)/L). No cases were complicated by intracranial hemorrhage, and there was no neonatal mortality. Platelet counts at birth of neonates born to mothers, who had first been diagnosed with ITP during pregnancy were significantly higher than those born to mothers diagnosed with ITP before pregnancy. There were significant correlations between neonatal platelet counts in the first and second siblings at birth (P = 0.015) and at nadir (P = 0.035). Platelet counts of neonates born vaginally were significantly more likely to decline after birth than those delivered by cesarean section (13/16 vs. 10/23, P = 0.024). In conclusion, diagnosis of ITP before pregnancy was significantly associated with neonatal thrombocytopenia, and the platelet count of an older sibling is a strong predictor for that of the next baby. The delivery mode may be an indicator of the timing of platelet count nadir after birth.