Postdelivery levels of anti-D IgG prophylaxis in D- mothers depend on maternal body weight.
BACKGROUND
Current recommendations for anti-D prophylaxis for women who deliver a D+ offspring vary from country to country, and the introduction of new reagents require pharmacokinetic studies that show serum levels after the injection. Serum levels of anti-D may depend on the maternal body mass index (BMI).


METHODS
Serum concentrations of total anti-D IgG and IgG1-4 subclasses were determined by flow cytometry in 26 D- women, who had received prophylaxis after delivery of a D+ offspring. Blood samples were drawn on Days 1, 2, 3, and 14 after injection, and the BMI was recorded.


RESULTS
Anti-D levels increased continuously in all women during the first 3 days. The increase was significantly affected by the BMI if higher than 27 kg per m2 (p<0.001). The higher the BMI, the less was the increase of serum anti-D. Mean peak levels 72 hours after injection was 89 ng per mL in lean women, but estimated levels were 28 to 60 percent lower in women with a BMI of 28 to 40 kg per m2. The effect of a BMI higher than 27 kg per m2 on anti-D was not gradual but progressive. Similarly, the BMI affected serum concentrations of anti-D subclasses IgG1-4 (p<0.001).


CONCLUSIONS
The BMI needs consideration for the adjustment of the dosage of anti-D, provided its bioavailability to suppress alloimmunization is reflected by measurable amounts in the serum.
Woelfer
Brigitte
B
Department of Obstetrics and Gynecology, Donauspital Vienna, Clinic for Blood Group Serology, University of Vienna, Austria.
Schuchter
Katharina
K
Janisiw
Michael
M
Hafner
Erich
E
Philipp
Karl
K
Panzer
Simon
S
D000328:Adult; D015992:Body Mass Index; D004899:Erythroblastosis, Fetal / Q000517:prevention & control; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000008:administration & dosage / Q000097:blood; D009035:Mothers; D010599:Pharmacokinetics; D049590:Postpartum Period / Q000097:blood*; D012203:Rh Isoimmunization / Q000517:prevention & control*; D018029:Rho(D) Immune Globulin / Q000008:administration & dosage* / Q000097:blood*; D013997:Time Factors
D007074:Immunoglobulin G; D018029:Rho(D) Immune Globulin