Thrombocytopenia in Small-for-Gestational-Age Infants

BACKGROUND: Thrombocytopenia is common among small-for-gestational-age (SGA) neonates (birth weight <10th percentile reference range), but several aspects of this thrombocytopenia are unclear, including the incidence, typical nadir, duration, association with preeclampsia, mechanism, and risk of death. METHODS: Using 9 years of multihospital records, we studied SGA neonates with ≥2 platelet counts <150 000/μL in their first week. RESULTS: We found first-week thrombocytopenia in 31% (905 of 2891) of SGA neonates versus 10% of non-SGA matched controls (P < .0001). Of the 905, 102 had a recognized cause of thrombocytopenia (disseminated intravascular coagulation, early-onset sepsis, or extracorporeal membrane oxygenation). This group had a 65% mortality rate. The remaining 803 did not have an obvious cause for their thrombocytopenia, and we called this “thrombocytopenia of SGA.” They had a mortality rate of 2% (P < .0001) and a mean nadir count on day 4 of 93 000/μL (SD 51 580/μL, 10th percentile 50 000/μL, 90th percentile 175 000/μL). By day 14, platelet counts were ≥150 000/μL in more than half of the patients. Severely SGA neonates (<1st percentile) had lower counts and longer thrombocytopenia duration (P < .001). High nucleated red cell counts at birth correlated with low platelets (P < .0001). Platelet transfusions were given to 23%, and counts typically more than tripled. Thrombocytopenia was more associated with SGA status than with the diagnosis of maternal preeclampsia. CONCLUSIONS: SGA neonates with clearly recognized varieties of thrombocytopenia have a high mortality rate. In contrast, thrombocytopenia of SGA is a hyporegenerative condition of moderate severity and 2 weeks’ duration and is associated with evidence of intrauterine hypoxia and a low mortality rate.