Routine Cord Blood Platelet Counts and Potential for Severe Neonatal Alloimmune Thrombocytopaenia (NAIT): A Cohort Study of 12 Yr. Experience at Middlemore Hospital, New Zealand

Abstract

Background: Neonatal alloimmune thrombocytopaenia (NAIT) is a rare but potentially serious condition where maternal antibodies result in destruction of foetal and neonatal platelets. At Middlemore Hospital in south Auckland, routine cord blood platelet counts were performed over many years.

Aims: These were twofold: To determine the prevalence of severe thrombocytopaenia (TP) and severe NAIT and investigate platelet counts in siblings of infants with TP.

Materials and Methods: Cord blood was collected on all hospital births over 500 g over a 12-year period (2005–2016) and term infants with TP (< 150 × 10⁹/L) selected. Records of infants with severe TP (< 50 × 10⁹/L) were reviewed for potential NAIT cases. Records of siblings of infants with any degree of TP were also reviewed to examine the potential for NAIT in affected families.

Results: Of 68910 births, 62083 platelet counts were suitable for analysis and 641 term infants had TP (1%) with 16 having severe TP (0.025%). NAIT or potential NAIT was judged clinically to be present in half of these (0.013%). Most cases were of European ethnicity with a Maori infant and a Tongan infant also being possible cases. No serious complications were identified. 5% of siblings of infants with TP had low counts with only one infant having a likely diagnosis of severe NAIT.

Conclusions: Severe TP was uncommon amongst infants born in south Auckland where mothers of Maori and Pacific Island ethnicity make up the majority of the population. Performance of routine cord platelet counts was of limited value in detecting potential cases of severe NAIT.