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

Inclusion Criteria:

• Pregnant and an estimated gestational age (GA) (based on ultrasound dating) fromWeek 13^0/7 to Week 16^6/7 at randomization

• History of severe Hemolytic Disease of the Fetus and Newborn (HDFN) in a priorpregnancy defined as:

1. documented fetal anemia, or received greater than or equal to (>=)1 IUT as aresult of HDFN or

2. fetal loss or neonatal death as a result of HDFN, with maternal alloantibodytiters 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, orRhC antigen with titers above the critical level (anti-Kell >= 4; other >=16) basedon 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 laboratory values within the study protocol-specified parameters: a)albumin, >=2.6 grams (g) per deciliter (g/dL), international system (SI): >=26 gramper liter (g/L); b) alanine transaminase (AST) less than or equal to (<=) 2 × upperlimit of normal (ULN); c) alanine transaminase (ALT) <=2 × ULN d) creatinine <=0.8milligrams per deciliter (mg/dL), SI: <=70.7 micromole per liter (μmol/L), and Serumtotal immunoglobulins G (IgG) ≥ 600 mg/dL SI: >=6 g/L

• Otherwise healthy on the basis of physical examination, medical history, vitalsigns, 12-lead ECG, and clinical laboratory tests performed at screening.

Exclusion Criteria:

• Currently pregnant with a multiple gestation (twins or more)

• Evidence of fetal anemia prior to randomization in the current pregnancy

• Current uncontrolled hypertension

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

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

• Has inflammatory or autoimmune diseases requiring immunosuppressive therapies thatmay jeopardize the safety of the participant

• Currently has a malignancy or has a history of malignancy within 3 years beforescreening (with the exception of localized basal cell carcinoma and/or squamous cellcarcinoma skin cancer that has been adequately treated with no evidence ofrecurrence for at least 3 months

• Is currently receiving systemic corticosteroids or other immunosuppressants fordisorders unrelated to the pregnancy

• Has received or planning to receive plasmapheresis, immunoadsorption therapy,intravenous immunoglobulin (IVIg), or any immunoglobulin (Ig)G fragmentcrystallizable (Fc)-related protein therapeutics during the current pregnancy

• Has a severe infection including opportunistic infections

• Presence of abnormal (protocol-specified) hematologic laboratory values duringscreening

• History of severe preeclampsia prior to GA Week 34 or severe fetal growthrestriction (estimated fetal weight <3rd percentile, based on local fetal growthnormative standards) in a previous pregnancy