Rh Immune Globulin helps prevent Hemolytic Disease of the Fetus/Newborn, but why is it so hard to decide how much to give?

Dr. Jessica Hudson

There is no doubt that the development and use of Rh Immune Globulin (RhIG) is one of the medical triumphs of the 20th century! It almost seems magical, really. The basic idea, if you don’t know, is that RhD-negative pregnant patients are at high risk of developing an antibody against the RhD antigen carried by their baby. The antibody, anti-RhD (or just “anti-D”) can cause hemolysis in that mom’s future RhD-positive babies, since the antibody crosses the placenta. The hemolysis has a long, awkward name: “Hemolytic Disease of the Fetus/Newborn” (HDFN).

RhIG to the Rescue!

The good news: RhIG, when given at the right time and in the right dose, does a wonderful job at preventing formation of anti-D in at-risk moms. In fact, in 99% of RhD-negative moms, the process is really, really simple. That mom gets RhIG at two times: First, at her 28 week OB visit, when we give her the contents of one prefilled syringe (or “vial”) of RhIG, and second, when we give her a second vial after she delivers an RhD-positive baby. Easy, right?

The BAD News

The bad news is what happens in the 1% of moms when things are not so simple. These are the RhD-negative moms who have a larger-than-normal exposure to their baby’s blood, and as a result, might need more than one vial of RhIG. Numerous studies have shown that those calculations (yes, there will be math in this situation!) are not always done accurately. This podcast is an attempt to simplify the calculations and make them memorable for learners.

This Episode is a New Start

Two things are unique about this episode. First, you are going to get to hear me in a live teaching session with one of my residents, Dr. Jessica Hudson, a third-year pathology resident at Loma Linda University. Second, this is the first episode where I am using a previous “Transfusion Medicine Question of the Day” from TransfusionNews.com as a starting point. If you aren’t signed up for the thrice-weekly, totally FREE Question of the Day series, you really should be! In fact, go there now and sign up!

The question you see below was written by Lorraine Blagg, MA, MLS(ASCP), SBB from Johns Hopkins, and is displayed here courtesy of TransfusionNews.com.

Dr. Jessica Hudson

There is no doubt that the development and use of Rh Immune Globulin (RhIG) is one of the medical triumphs of the 20th century! It almost seems magical, really. The basic idea, if you don’t know, is that RhD-negative pregnant patients are at high risk of developing an antibody against the RhD antigen carried by their baby. The antibody, anti-RhD (or just “anti-D”) can cause hemolysis in that mom’s future RhD-positive babies, since the antibody crosses the placenta. The hemolysis has a long, awkward name: “Hemolytic Disease of the Fetus/Newborn” (HDFN).

RhIG to the Rescue!

The good news: RhIG, when given at the right time and in the right dose, does a wonderful job at preventing formation of anti-D in at-risk moms. In fact, in 99% of RhD-negative moms, the process is really, really simple. That mom gets RhIG at two times: First, at her 28 week OB visit, when we give her the contents of one prefilled syringe (or “vial”) of RhIG, and second, when we give her a second vial after she delivers an RhD-positive baby. Easy, right?

The BAD News

The bad news is what happens in the 1% of moms when things are not so simple. These are the RhD-negative moms who have a larger-than-normal exposure to their baby’s blood, and as a result, might need more than one vial of RhIG. Numerous studies have shown that those calculations (yes, there will be math in this situation!) are not always done accurately. This podcast is an attempt to simplify the calculations and make them memorable for learners.

This Episode is a New Start

Two things are unique about this episode. First, you are going to get to hear me in a live teaching session with one of my residents, Dr. Jessica Hudson, a third-year pathology resident at Loma Linda University. Second, this is the first episode where I am using a previous “Transfusion Medicine Question of the Day” from TransfusionNews.com as a starting point. If you aren’t signed up for the thrice-weekly, totally FREE Question of the Day series, you really should be!

About My Guest:

Jessica Hudson MD is, as of this recording, a third-year pathology resident at Loma Linda University in Loma Linda, CA. She is a Southern California native who loves all things adventure and Transfusion Medicine. She and her husband enjoy snowboarding, line dancing, singing in the car, as well as everything related to “the classics” (Star Wars, Lord of the Rings, and Harry Potter).

DISCLAIMER: The opinions expressed on this episode are those of my guest and I alone, and do not reflect those of the organizations with which either of us is affiliated. Neither Dr. Hudson nor I have any relevant financial disclosures.

Further Reading:

Thanks to:

  • Dr. Jessica Hudson: For being the first resident to be a part of this podcast, and for trusting me not to embarrass her (not sure I succeeded, but I tried!).

Music Credit

Music for this episode includes “Cuando te invade el temor” and “Reflejo,” both by Mar Virtual via the Free Music Archive. Click the image below for permissions and license details.
Creative Commons license and link

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