A Study of Nipocalimab in Reducing the Risk of Fetal and Neonatal Alloimmune Thrombocytopenia (FNAIT)

Inclusion Criteria:

• Pregnant and an estimated gestational age (GA; based on ultrasound dating) from Week 13 to 18 at randomization

• Has a history of greater than or equal to (>=) 1 prior pregnancy with fetal andneonatal alloimmune thrombocytopenia (FNAIT) (including neonatal platelet count lessthan (<) 150×10^9/Liter) with none of them affected by fetal/neonatal intracranialhemorrhage (ICH) or severe hemorrhage based on medical records

• Current pregnancy with presence of maternal anti- human platelet antigen (HPA)-1aalloantibody and positive fetal HPA-1a genotype as confirmed by cell-free fetaldeoxyribonucleic acid (DNA) in maternal blood

• Health status considered stable by the investigator based on physical examination,medical history, vital signs, 12-lead Electrocardiogram (ECG), and clinicallaboratory tests performed at screening

• For maternal participant and neonate/infant, willing to forego participation inanother clinical study of an investigational therapy until the last follow-up visit

Exclusion Criteria:

• Currently pregnant with multiple gestations (twins or more)

• History of severe preeclampsia in a previous pregnancy

• History of myocardial infarction, unstable ischemic heart disease, or stroke

• Known allergies, hypersensitivity, or intolerance to nipocalimab or its excipients (refer to the Investigator Brochure (IB))

• Has any confirmed or suspected clinical immunodeficiency syndrome or has a familyhistory of congenital or hereditary immunodeficiency unless confirmed absent in theparticipant