00:00
Alright, our last bit of business today is to talk about Rh incompatibility. Yes, I know
there are 2 types of the blood, there is the A, O, B, AB, and then there's the Rhesus. The
reason we talk about Rh incompatibility because incompatibility between the blood type is
usually very rare and insignificant in terms of causing complications. Rh incompatibility,
however, can cause significant complications which is why we're going to talk about it. So,
taking you back to a little bit of physiology and we think about antibodies that are produced.
00:34
If we have a patient who is Rh negative, they don't have antibodies in their system. If they
become pregnant with a baby that is Rh positive and for some reason there is a mixing of the
blood, now normally maternal blood and fetal blood don't mix so that's not the way that it's
set up. But sometimes during testing, think about that CVS, think about that amniocentesis,
think about someone who has experienced saying bleeding during the first trimester, there
may be a little fetal blood that gets mixed in to that maternal system. And if that happens,
the maternal bloodstream responds by producing antibodies. And the type of antibodies
that are produced are called IgM antibodies. So that is a normal immunologic response to a
foreign body. Now, IgM antibodies are really large, they're big and they can't cross over the
the placenta. So, they will hang out in mom's bloodstream and that's completely fine and
there won't be any problem with that fetus. So that fetus will be delivered and go on and do
great things. Now, during a subsequent pregnancy, if there is another exposure of fetal and
maternal blood, there is a memory going on. Right? So instead of IgM antibodies, IgG
antibodies are produced. They are not big, they are small and yes they can cross over the
placenta. And so when they cross over the placenta, they will actually attack the fetus and
can lead to a myriad of complications. So, what do we do about it? We give a medication
called Rhogam, and Rhogam is actually, for lack of a better way to explain, it's a pretend
antibody. And it fools the body into thinking that it's made antibodies so it doesn't do it. And
then these antibodies disappear after 14 weeks and it's like the whole thing never happen.
02:25
So, the mother never produces IgM antibodies that then turn into IgG antibodies and so
during the next pregnancy it's like the first time all over again. Okay? So we give Rhogam at
28 weeks, we give Rhogam at delivery to make sure that the mother does not produce IgM
antibodies. Okay? So, the reason why this is particularly important is that if you have a
patient who is bleeding in the first trimester, we want to make sure that they get Rhogam.
02:56
Right? If you have a patient who is coming in at 28 weeks and you find out they're Rh
negative, you want to make sure they get Rhogam. If you have a patient on the postpartum
unit who is Rh negative after we've confirmed that the fetal blood type is positive, you
want to make sure that they give Rhogam. So here are the things you want to remember one
more time. Rhogam suppresses antibody formation in the maternal bloodstream. It's given
at 28 weeks, it's given 72 hours after delivery after we confirm the blood type of the baby,
and it's given before any invasive procedures like CVS and amniocentesis. Last little bit,
remember, if we have any first trimester bleeding or spontaneous abortion and we have a
patient who is Rh negative, we want to make sure that they also receive Rhogam. Sometimes
this is forgotten and this sets up someone for sensitization which has big implications for
subsequent pregnancies.