The incidence and outcome of clinically significant antibodies detected in Rhesus-D positive pregnant women of the...

Haemolytic disease of the fetus/newborn secondary to clinically significant non-Rhesus-D antibodies has risen in importance since the advent of immunoprophylactic anti-D administration to Rhesus-D negative women. Of interest is the incidence of these antibodies in Rhesus-D positive women, who receive less frequent antenatal alloantibody screening. This is of particular concern if the antibodies arise late in pregnancy and may go undetected.

To assess the proportion of Rhesus-D positive pregnant women with late developing clinically significant antibodies for haemolytic disease of the fetus/newborn, and whether these resulted in adverse fetal outcomes.

A retrospective analysis over a 12-month period at a tertiary hospital in the Northern Territory. Group and antibody screen results in addition to clinical data regarding pregnancy/newborn were collected.

Sixty-four of 2612 women (2.5%) had red blood cell antibodies detected during their pregnancy. Of these, 21 clinically significant antibodies were detected in 19 women (0.7% of initial cohort). The most common antibody detected was anti-c (28.5%). In six of these women (0.23% of initial cohort), the antibodies were late developing. Mild jaundice was noted in three newborns with phototherapy required in one.

Although clinically significant antibodies were detected during pregnancy, and in a small proportion of cases as a late developing antibody undetected in the first trimester screening, clinical outcomes for the newborn were mild. As such, the cost of retesting all Rhesus-D positive pregnant women in the third trimester would be considerable and unlikely to result in any meaningful clinical benefit.