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Fruit of the Womb
Fruit of the Womb

Readers' Questions Regarding Rh-immune Globulin

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Like GBS (see our last post), another common source of questions and confusion in uncomplicated pregnancies is the significance of being an Rh-negative woman. It is another one of those things we screen for routinely, and when found, add to our 'problem lists', but rarely get around to explaining well enough to our patients that they understand why they are being given a 'shot' at 28 weeks and after delivery (and sometimes more often than that). In previous posts we have provided some explanations for all of the above, but questions still arise on a regular basis. Below are two recent comments from readers that include questions many pregnant women may have, but may be afraid to ask their providers, related to the use of Rh-immune globulin to prevent sensitization in pregnancies at risk because a baby may be Rh-positive. Again, to the readers who left the comments, I apologize for editing their posts to the best of my understanding so that others may appreciate their concerns...

• At Tue Dec 04, 01:43:00 PM 2007, Teri said…

I was 2 months along when I found out that I was pregnant. I went to the emergency room after my body rejected my baby (spontaneous miscarriage). They informed that I have Rh-negative blood. They gave me a shot that sounded like 'rogain' and told me it would prevent antibodies from attacking my baby in my next prgnancy. Is that what the shot is for? Will it affect me if my future baby's father is Rh-negative also?


• At Fri Dec 14, 12:50:00 PM 2007, Kenneth F. Trofatter, Jr., MD, PhD said…

To Teri Dec 4: Sorry about your miscarriage. You received Rhogam which is Rh-immune globulin that contains antibodies to Rh-positive blood cells. That helps your body destroy any Rh-positive red blood cells that might have gotten into your blood stream from the pregnancy and helps prevent you from developing antibodies of your own (just as the doctors told you in the ER). If the baby's father is Rh-negative too, then the baby could not be Rh-positive and you did not need the Rhogam, but it will not hurt that you got it either, now or with future pregnancies. In your next pregnancy, tell your doctor that you would like to have the baby's father's blood type tested as well. If he is indeed Rh-negative, then you won't need any 'Rhogam shots' during or after the pregnancy. Just be sure you "know who the Daddy is!" Thanks for your question!
Dr T


• At Thu Dec 06, 05:49:00 PM 2007, HAYAT said…
Hi. I'm 31 weeks pregnant. Today I had the Rhogam shot because I am O-negative. I didn't know what it is. I did search on the net and found out that I should have had it at 28 weeks? I am so worried. Is it too late for this shot? My doctor did take my blood before giving me the shot to perform an antibody screen? She gave me the shot after taking my blood. Does that mean I didn't develop the antibodies against the Rh-D antigen? I'm so confused and so sad. Can you please explain to me and tell me if my baby is at risk? And why didn't they give me the shot at 28 weeks. I'm sorry for my english if I made mistakes.
My name is HAYAT
THANK YOU

• At Fri Dec 14, 12:55:00 PM 2007, Kenneth F. Trofatter, Jr., MD, PhD said…

To Hayat Dec 6: See my explanation above to our first reader. The 'shot' is Rh-immune globulin that contains antibodies against Rh(D)-positive red blood cells. That way, if the baby is Rh-positive and any of its red blood cells get into your circulation, the antibodies will help to destroy those cells before you have a chance to make your own antibodies to them. If you do develop your own antibodies, that is called alloimmunization (or isoimmunization). We frequently refer to that as 'sensitization' as well.

If you had not developed any antibodies before you got the shot, then you can stop worrying. The shot will help protect you from becoming sensitized during the rest of your pregnancy. We generally recommend giving the shot at 28 weeks because very few women will become sensitized before that time and the Rh-antibodies usually hang around until about 40 weeks (full term). The shot does not have to be given right at 28 weeks! Some folks give it a little earlier, and some a little later. Women who have trauma, bleeding, or other invasive procedures (such as an amniocentesis) may receive several 'shots' during there pregnancies. One injection of 'Rhogam 300mcg' will neutralize about 30 cc of whole fetal blood. The important thing is that you did get it in time. You should be fine! After delivery, if your baby does turn out to be Rh-positive, your doctors may check your blood to see how much of the baby's blood got into your circulation and then adjust the amount of Rh-immune globulin to make sure you eliminate the fetal red blood cells. Good luck with the rest of your pregnancy and let us know how things turn out!
Dr T
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