Background: Anti-D immunoglobulin (Ig) is routinely administered to Rh-negative mothers postpartum to prevent alloimmunization. Accidental administration to Rh-positive newborns is exceedingly rare, with only six cases documented in the literature. Of these, three developed mild to moderate hemolytic anemia.Case Presentation Summary: We report the case of a term male newborn, delivered via cesarean section for arrest of labor. Birth weight was appropriate for gestational age (2990g; 21st percentile). Apgar scores were 9/10/10, with good adaptation to extrauterine life. Standard neonatal prophylaxis was administered, including intramuscular vitamin K and ocular antibiotic prophylaxis with chloramphenicol. The direct antiglobulin test (DAT) at birth was negative. The infant was exclusively breastfed and exhibited normal urinary and bowel function. A physical examination performed at 11 hours of life revealed no abnormalities. The infant was blood group O Rh-positive, born to a group A Rh-negative mother.At approximately 12 hours of life, a 300 μg intramuscular dose of anti-D immunoglobulin, intended for the mother, was inadvertently administered into the infant’s left deltoid muscle. The newborn was promptly admitted to the neonatal unit for clinical and laboratory monitoring. At 13 hours of life, repeat testing showed a now positive DAT, though complete blood count, serum electrolytes, liver function tests were all within normal limits and peripheral blood smear showed no morphological abnormalities. Pediatric Hematology and Immunohematology services were consulted. Laboratory evaluations were repeated at 22 hours, and on days 2, 4, and 9 of life, showing no evidence of anemia, hemolysis, or other significant abnormalities. At follow-up on day 9, the infant remained clinically well, with normal examination findings.Due to the prolonged effect of intramuscular anti-D Ig, further laboratory monitoring is scheduled at one month of life. Current literature advises deferring administration of live vaccines for 3 to 6 months following intramuscular immunoglobulin exposure. However, this restriction does not apply to oral live vaccines, such as rotavirus. The first live attenuated vaccine in the Portuguese National Immunization Program, MMR (measles, mumps, and rubella), is scheduled at 12 months of age, requiring no modifications to the standard vaccination schedule.Learning Points Discussion: This case highlights a rare event of inadvertent administration of anti-D immunoglobulin to a Rh-positive newborn, without subsequent development of hemolytic anemia. It underscores the critical need for stringent medication administration protocols and the active involvement of institutional risk management and patient safety teams. Reporting similiar cases is essential to enhance understanding of potential consequences and clinical management strategies.
