Optimizing hemolytic disease management with third-trimester screening
Third-trimester red blood cell (RBC) antibody screening in pregnant women who are Rhc-negative contributes to the timely detection and treatment of severe hemolytic disease of the fetus and newborn (HDFN). It also likely leads to a decrease in the incidence of severe HDFN, according to researchers who analyzed data from the Dutch national screening program.
The nationwide cohort study reviewed data prospectively collected between October 1, 2011 and October 1, 2013 from 62,096 Rhc-negative women without RBC antibodies at first trimester screening and their offspring.1 Late alloimmunization (presence of newly detected, clinically relevant RBC antibodies at week 27 of pregnancy) occurred in 99 women (0.16%), of whom 91% developed c and/or E antibodies.
There were 22 cases of HDFN in the overall population, of which 2 (0.003%) were severe (disease needing intervention with intrauterine transfusion and/or neonatal exchange or blood transfusions in the first week after birth) and 20 (0.032%) were moderate (need for treatment of neonatal jaundice with phototherapy only). Rates of severe and moderate HDFN in the late alloimmunization subgroup were 2% and 22.5%, respectively.
There were no fetal or neonatal deaths in the series. The number needed to screen to detect one case of HDFN was calculated to be 2823, and the number needed to screen to detect one severe HDFN case was 31,048.
“In the Netherlands, the current alloimmunization screening protocol for pregnant women involves a first trimester assay for RBC antibodies and repeat screening at 27 weeks’ gestation for RhD-negative and Rhc-negative women. The second screening of Rhc-negative women, who account for almost 20% of the population, was implemented in July 2011 after it was recognized that four cases of severe HDFN were missed with the first trimester screening annually due to late Rhc immunization,” explained Yolentha Slootweg, MSc, department of obstetrics, Leiden University Medical Centre, Leiden, the Netherlands.