Clinical and laboratory predictors of fetal and neonatal alloimmune thrombocytopenia

Transfusion. 2022 Nov;62(11):2213-2222. doi: 10.1111/trf.17144. Epub 2022 Oct 14.


Background: Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is the most common cause of intracranial hemorrhage (ICH) in thrombocytopenic term infants. We investigated clinical and laboratory predictors of severe FNAIT in a tertiary care referral center.

Study design and methods: Retrospective cohort study over a 30-year period. We defined FNAIT as recurrence of neonatal thrombocytopenia in a subsequent pregnancy; and severe outcomes as any of: (1) a birth platelet count below 20 × 109 /L; (2) ICH or (3) fetal death. We used a generalized estimating equations analysis and classification tree analysis to identify risk factors for severe FNAIT in a subsequent pregnancy.

Results: During index pregnancies (n = 135 in 131 mothers), 71 infants (52.6%) had severe outcomes including a platelet count <20 × 109 /L (n = 45), fetal or neonatal ICH (n = 32), or fetal death (n = 4). During subsequent pregnancies (n = 72), 15 infants (20.8%) had severe outcomes including birth platelets <20 × 109 /L (n = 10), ICH (n = 2), or death (n = 3). Forty-two women (58.3%) received antenatal intravenous immune globulin (IVIG) during subsequent pregnancies. Eight mothers (n = 9 infants) had severe FNAIT outcomes despite receiving antenatal IVIG. Maternal antibodies to human platelet antigens (HPA) was the only independent predictor of severe FNAIT in a subsequent pregnancy (OR = 25.3, p = .004). Nevertheless, one of 43 infants from antibody-negative mothers had a severe outcome.

Conclusions: The presence of anti-HPA is highly indicative of the diagnosis of severe FNAIT; however, we observed one infant who had severe FNAIT recurrence, defined using strict clinical criteria, without a maternal antibody. Improved diagnostic and therapeutic strategies are needed to prevent severe FNAIT in high-risk mothers.

Keywords: FNAIT; pregnancy; thrombocytopenia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies
  • Antigens, Human Platelet*
  • Female
  • Fetal Death
  • Humans
  • Immunoglobulins, Intravenous / therapeutic use
  • Infant, Newborn
  • Infant, Newborn, Diseases*
  • Intracranial Hemorrhages / diagnosis
  • Intracranial Hemorrhages / etiology
  • Pregnancy
  • Retrospective Studies
  • Thrombocytopenia, Neonatal Alloimmune*


  • Immunoglobulins, Intravenous
  • Antigens, Human Platelet
  • Antibodies