A Study of Nipocalimab in Pregnancies at Risk for Severe Hemolytic Disease of the Fetus and Newborn (HDFN)

The purpose of this study is to assess the effectiveness of nipocalimab when compared to placebo in decreasing the risk of fetal anemia (a condition in which a baby's red blood cell volume falls below normal levels while the baby is developing in the womb) with live neonates in pregnant participants at risk for severe hemolytic disease of the fetus and newborn.

Inclusion Criteria: * Pregnant and an estimated gestational age (GA) (based on ultrasound dating) from Week 13\^0/7 to Week 18\^6/7 at randomization * History of severe Hemolytic Disease of the Fetus and Newborn (HDFN) in a prior pregnancy defined as documented: 1. fetal anemia as result of HDFN or fetal hydrops as result of HDFN or received greater than or equal to (\>=)1 IUT as a result of HDFN or 2. fetal loss or neonatal death as a result of HDFN, with maternal alloantibody titers for Rhesus antigen D protein (RhD), Kell, Kell Rhesus antigen C protein (Rhc), Rhesus antigen E protein (RhE), or RhC antigen above the critical levels (anti-Kell \>=4; other \>=16) and evidence of an antigen-positive fetus * During the current pregnancy, presence of maternal alloantibody to RhD, Rhc, RhE, or RhC antigen with titers above the critical level (anti-Kell \>= 4; other \>=16) based on the designated central lab results at screening * Evidence of antigen-positivity corresponding to the current maternal alloantibody (RhD, Kell, Rhc, RhE, or RhC) confirmed by non-invasive antigen cell-free fetal DNA (cffDNA) performed at the central laboratory * Have screening lab test results within values within the study protocol-specified parameters: a) albumin \>= lower limit of normal (LLN); b) alanine transaminase (AST) less than or equal to (\