Fetal thrombocytopenia in pregnancies complicated by fetal anemia due to red-cell alloimmunization: cohort study and meta-analysis

Objective To estimate the prevalence and characteristics of fetal thrombocytopenia at the time of percutaneous umbilical cord sampling (PUBS) in pregnancies complicated by alloimmunization and to conduct a systematic review on fetal thrombocytopenia in these pregnancies. Study design Retrospective cohort study of all patients undergoing PUBS at our institution from 2000-2017. Clinical data, including fetal platelet counts, were abstracted from the medical record and analyzed with routine statistical procedures. A systematic review and meta-analysis were also conducted according to standard procedures. Result At first procedure, prior to any transfusion, 13/36 fetuses (36%) had thrombocytopenia: 11/36 (31%) had moderate thrombocytopenia and 2/36 (6%) had severe thrombocytopenia (14 patients had no platelet count at first procedure). The systematic review identified six studies, and the prevalence of fetal thrombocytopenia at the time of PUBS for alloimmunization was 18% (95% confidence interval 11%, 26%). Conclusion Thrombocytopenia is common and underappreciated in fetuses undergoing PUBS for alloimmunization.