A patient presents with vaginal bleeding, positive pregnancy test, and estimated to be at 7 weeks of gestation. Physical exam and pelvic ultrasound are diagnostic of spontaneous abortion. She is hemodynamically stable with mild bleeding and appropriate for outpatient treatment. Does she need to wait for blood type to assess the need to administer RhD immunoglobulin (e.g., RhoGAM)?

Approximately 15 percent of individuals in North America are RhD-negative. When an RhD-negative pregnant person is carrying an RhD-positive fetus, this exposure results in production anti-D antibodies, placing future pregnancies at risk for RhD alloimmunization. Enter RhD immunoglobulin. The introduction of RhD immunoglobulin in the 1970s resulted in a drastic reduction in the rate of fetal and neonatal morbidity and mortality worldwide due to hemolytic disease of the fetus and newborn (HDFN).¹ The proven benefit to RhD prophylaxis is in the routine prophylaxis performed in the setting of prenatal and postpartum care (typically at 28 weeks of gestation and post-partum if the newborn is RhD-positive). However, emergency physicians often care for patients with vaginal bleeding in the first trimester and/or early pregnancy loss, prior to the 28-week prophylactic dose. As a result, the treatment of spontaneous or induced abortions in the Emergency Department (EDs) historically involved assessing the pregnant patient’s blood type and Rh status and administering RhD immunoglobulin if RhD negative. This is time consuming in packed EDs, more costly, and wasteful, as the proper dose of RhD immunoglobulin for this type of patient (50 μg) is less widely available than the 300 μg dose.

In 2017, the American College of Obstetrics and Gynecology (ACOG) did indeed recommend that RhD immune globulin should be considered in first-trimester spontaneous abortion, particularly those further along in the first trimester (expert opinion).² Recommendations were stronger for those who receive instrumentation for treatment of the abortion and for those who had either medical or surgical pregnancy termination. More recently, however, multiple professional society guidelines have opposed routine use in individuals less than 10 to 12 weeks of gestation, including the World Health Organization, the Society of Obstetricians and Gynaecologists of Canada, the Society of Family Planning, the National Institute for Health and Care Excellence Abortion Care, and others.^3,4 In 2024, ACOG completely reversed their prior recommendation: “ACOG suggests forgoing routine Rh testing and RhIg prophylaxis” in patients less than 12 weeks (and zero days) of gestation experiencing pregnancy loss or undergoing abortion.⁵

What prompted the ACOG change?

Re-examination of the data that this specific recommendation was based on (i.e., none) coupled with new data and external circumstances likely prompted the new recommendation. Like many therapies in pregnancy, we lack rigorous, controlled data evaluating the routine practice of RhD immunoglobulin administration in first trimester abortions (spontaneous or induced). The only randomized placebo-controlled trial to date, published in 1972, found no evidence of Rh isoimmunization in spontaneous abortions but was too small to capture rare events.⁶ Imperfect population-level data found no increase in prevalence of clinically significant anti-D perinatal antibodies in the Netherlands (no RhD prophylaxis for spontaneous abortions less than 10 weeks or induced abortions less than 7 weeks) compared with Canada (RhD prophylaxis in all first trimester abortions in Rh-negative patients). Further, the best data to date suggest no relationship between first-trimester abortion and change in fetal red blood cell (fRBC) count that would result in sensitization (125 fl RBCs/5 million total RBCs). In prospective cohort study of 506 pregnant individuals undergoing first-trimester abortion care evaluated pre-abortion and post-abortion fRBC count by flow cytometry. In this cohort of individuals with a mean gestational age of just over 7 weeks, no participants (0 percent; 95 percent CI,0 percent-0.59 percent) had newly elevated fRBC counts above the sensitization threshold post-abortion. Three participants (0.6 percent) had levels above the sensitization threshold pre-abortion, and 1 (0.2 percent) continued to have a fRBC count above the threshold post-abortion.⁷