Rho(D) Immune Globulin (anti-D) Concentration-Time Curve After Antenatal Immunoprophylaxis in RhD-Negative Pregnant Women

Abstract Objectives: To assess anti-D concentration through maternal indirect antiglobulin test (IAT) titers and scores after RhD-negative pregnant women receive antenatal anti-D until delivery. Methods: Cross-sectional study. Twenty-seven RhD-negative pregnant women were evaluated after receiving a prenatal anti-D dose around 28th week of pregnancy. Serial blood samples were collected at 3, 7, 21, 42, 63 and 84 days after anti-D administration. We performed IAT by conventional tube test (CTT) and gel microcolumn assay (GMA) to assess anti-D scores and titers. Statistical analyzes were performed using IBM SPSS Statistics software. Results: Anti-D had maximum scores values ​around 7 days after its administration, and scores were higher in GMA than CTT for all patients. Anti-D was detected at delivery in 59% of the participants by IAT performed in GMA. Overweight and obese pregnant women may present lower concentrations of anti-D. No correlation was found between maximum scores when comparing them with these variables: newborn RhD blood type; maternal-fetal ABO incompatibility and the number of pregnancies. Conclusions: Administering 300 μg of anti-D in 28th week of pregnancy should be compared in studies analyzing perinatal outcomes, since anti-D was not detectable in 41% of patients, suggesting a significant period without prophylaxis.