The administration of Rh immunoglobulin (RhIg), a human blood derived antibody, is a common procedure during bleeding events in pregnancy. RhIg is used to prevent pregnant individuals whose blood is Rh-negative from having an immune response to their Rh-positive fetus—which is also referred to as Rh sensitization. But is Rh treatment necessary for individuals undergoing induced first-trimester abortion care? The answer to this question is important because its routine use creates significant financial barriers to care. 

Some organizations like the World Health Organization (WHO), have released abortion care guidelines that suggest Rh testing and immunoglobulin administration are unnecessary before an induced first-trimester abortion. However, there is a general lack of data to confirm these claims. 

In a new study by LDI Senior Fellow Courtney A. Schreiber and colleagues, such concerns about the role of RhIg treatment in abortion care guidelines are addressed with empirical evidence.

Using maternal blood samples from 506 participants before and after an induced first-trimester abortion, researchers concluded that Rh testing and immunoglobulin administration is unnecessary after induced first-trimester abortion. These study results also suggest ways to reduce financial and clinical barriers to abortion care. 

To learn more about the study, we asked Dr. Schreiber a series of questions below.

What is Rh testing and why is it becoming increasingly important for patients to know about? 

Schreiber: There is global consensus that there is a benefit to providing Rh immunoglobulin in the third trimester to prevent immune sensitization and pregnancy complications, but evidence to guide the management of Rh-negative women with first-trimester bleeding has been lacking. The rationale behind Rh testing and preventative care at early gestational ages is rooted in studies from the 1970s that used now-obsolete techniques to measure the risk of isoimmunization (i.e., the initiation of an immune response against the biological content of another human individual, or Rh sensitization). Given that Rh immunoglobulin is a human blood product and that tests and treatment have costs, patients with bleeding episodes in pregnancy may wonder if these tests and treatments are necessary.

How do guidelines vary for providing Rh testing and why is that important? 

Schreiber: The World Health Organization (WHO), Society of Family Planning (SFP), and Royal College of Obstetricians and Gynecologists (RCOG) recommendations have recently changed and now recommend to forgo Rh testing and RhIg treatment at less than 12 weeks of gestation. The American College of Obstetricians and Gynecologists (ACOG) still recommends Rh testing and RhIg treatment despite citing the lack of evidence in support of this practice.

What do you consider to be your most important findings?

Schreiber: Our study shows that Rh testing and the provision of Rh immunoglobulin should not be for bleeding episodes in pregnancy less than 12 weeks of gestation. As is often true in science, our results surprised us because we found that not only were nearly all fetal red blood cell (fRBC) counts far below the threshold, which we hypothesized, but they did not change before versus after abortion, irrespective of the threshold.

In this prospective study, 505 out of 506 participants (99.8%) undergoing induced first-trimester abortion care had post-procedure fRBC counts below the published threshold for Rh sensitization. No participants crossed this threshold after induced abortion; the single participant who exceeded the threshold post abortion also exceeded the threshold at baseline (i.e., before the abortion).

In this study, post-abortion fRBC counts were not correlated with gestational age, gravidity, parity, prior vaginal bleeding in pregnancy, or other demographic factors.

How does Rh testing and the administration of Rh immunoglobulin create financial and clinical barriers to abortion care access?

Schreiber: We have an economic analysis forthcoming, so please stay tuned! Blood typing and subsequent RhIg administration raise the cost of each abortion and increase demands on both patients and providers, particularly in settings where insurance coverage is limited. People across the world, and particularly in the U.S., face  numerous personal, legal, and financial challenges to safe, evidence-based health care. Removing the cost of unnecessary testing will help reduce financial and time barriers.

These burdens extend beyond abortion, affecting all pregnant individuals who seek care for first-trimester bleeding, which is delivered in diverse settings by many providers, including those in emergency medicine, family medicine, internal medicine, and pediatrics. Individuals experiencing first-trimester miscarriage, which affects hundreds of thousands of patients per year, also receive Rh testing and preventative care. The reduction of costly and unnecessary practices could streamline care delivery and improve the allocation of resources in all settings in which early pregnancy care is delivered.

What were your experiences like conducting this study?

Schreiber:  Besides generating data that will improve the care of patients and support high-value care, this was a joyful team-science, cross-disciplinary collaboration. Every member was deeply committed to generating the highest quality science. We had so much fun! We are so grateful to the participants for their contributions and willingness to undergo extra blood draws.

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The study, “Induced Abortion and the Risk of Rh Sensitization,” was published on September 26, 2023 in JAMA. Authors include Sarah Horvath, Zhen-Yu Huang, Nathanael C. Koelper, Christian Martinez, Patricia Y. Tsao, Ling Zhao, Alisa B. Goldberg, Curtiss Hannum, Mary E. Putt, Eline T. Luning Prak, and Courtney A. Schreiber.

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