Rh testing or immunoglobulin administration following induced first-trimester abortion not necessary: JAMA

Rh testing and therapy are not indicated before to 12 weeks' gestation since induced first-trimester abortion is not a risk factor for Rh sensitization, says an article published in the Journal of American Medical Association.

Rh immunoglobulin is not essential until 12 weeks of pregnancy, according to population-level statistics, however there is little clinical support for this idea. As a result, recommendations change, leaving the dangers and advantages of Rh testing and therapy unclear. This study by Sarah Horvath and colleagues assessed how frequently maternal exposure to fetal red blood cells (fRBCs) in induced first-trimester abortion surpasses the most conservative reported threshold for Rh sensitization.

High-throughput flow cytometry was used to identify circulating fRBCs in matched maternal blood samples taken before and after an induced first-trimester abortion (either medically or surgically). Before 12 weeks and 0 days of gestation, those who had an induced first-trimester abortion were included. 506 patients who experienced either a medical (n = 319 [63.0%]) or procedural (n = 187 [37.0%]) abortion were able to provide paired blood samples. The percentage of subjects with fRBC counts over the sensitization threshold (125 fRBCs/5 million total RBCs) following an induced first-trimester abortion served as the main outcome.

The key findings of this study were:

The average (SD) age of the 506 participants was 27.4 (5.5) years; 313 (61.9%) of them were Black, and 123 (24.3%) were White.

Three of the 506 participants had high fRBC levels at the beginning of the study, and one of these patients also had a high fRBC count after the abortion.

After an induced first-trimester abortion, no additional subjects showed raised fRBC counts beyond the sensitization threshold.

The 99th percentile and higher 95th percentile had values of 24 and 35.6 fRBCs, respectively, with the median change from baseline being 0 fRBCs.

No other baseline attribute was substantially linked with post-abortion fRBC count, despite the fact that there was a considerable correlation between the pre-abortion and post-abortion fRBC counts.

Reference:

Horvath, S., Huang, Z.-Y., Koelper, N. C., Martinez, C., Tsao, P. Y., Zhao, L., Goldberg, A. B., Hannum, C., Putt, M. E., Luning Prak, E. T., & Schreiber, C. A. (2023). Induced Abortion and the Risk of Rh Sensitization. In JAMA (Vol. 330, Issue 12, p. 1167). American Medical Association (AMA). https://doi.org/10.1001/jama.2023.16953