Rh immunoglobulin routinely given to Rh-negative pregnant women during the second and third trimesters has reduced the maternal Rh sensitization rate from 10% to 0.2%. Guidelines are variable for Rh immunoglobulin use during the first trimester, so many clinicians still test and treat pregnant women during this time. To determine if Rh immunoglobin treatment is necessary for Rh-negative women undergoing first-trimester induced abortions, researchers in the U.S. enrolled 506 Rh-negative women (mean age, 27 years; 62% Black, 24% White) in their first trimester. Fetal RBCs (fRBCs) were analyzed by flow cytometry both before and after the induced abortion. None of the women had newly elevated fRBC counts above the sensitization threshold (125 fRBCs/5 million total RBCs), and only one woman had elevated counts after the abortion (0.2%; 95% C.I., 0% to 0.9%), suggesting that Rh testing and treatment are not necessary in the first trimester. These data support the World Health Organization’s guideline to forgo Rh testing and treatment prior to abortions at less than 12 weeks gestation.
Reference:
