9 things you might not know about anti-D…

small_50451811Maybe you’re already full of information about anti-D, but as I was writing my anti-D resources series, I started noting a few things down that people are sometimes surprised to discover when I speak about this topic.  If you’re completely new to this area, you might want to start by reading the anti-D resources series first and/ or checking out my book on this topic.

1. It’s a blood product…

Actually, most of the people who need to give anti-D or consider whether they want to receive anti-D do know this now, but this has changed in the time since I first became interested in this topic.  Previously, there was a real lack of awareness that anti-D was manufactured from human blood – and pooled blood at that – and this lack of awareness poses a real threat to women being able to make an informed choice.  While women will often question the need for a blood transfusion, they rarely question the need for anti-D, which begs the question of whether they really know what they are being offered.  The reality is that most women will want anti-D anyway, but they have a right to know exactly what they are being offered.

2. It works more effectively than the vast majority of drugs used in maternity care…

I think this is an important one to note near the top as well, because I am often misquoted as saying women should decline anti-D or that anti-D doesn’t work.  Au contraire.  Postnatal anti-D is incredibly effective, although the evidence on antenatal anti-D is, according to the Cochrane review in this area, of low to very low quality.  The issue is that it’s not necessary for all rhesus negative women who have given birth to rhesus positive babies.  This is because, as the original studies in this area show, only around ten per cent of rhesus negative women who have given birth to a rhesus positive baby will become isoimmunised if they do not have it.  Unfortunately, because of the decisions made following the original clinical trials on this (which you can read about in my book or in this article), we don’t have much information about who is more or less likely to need it.  And I believe that women have the right to all the facts before they make decisions.

3. We can speculate a bit about who may be at greater or lesser risk, though…

While the evidence is either indirect (in this case extrapolated from studies of related areas) or anecdotal/experiential and based on the observations and experiences of midwives, doctors, women and their families, it would appear that less may be more when it comes to interventions.  The theory is that anything that could interfere with the integrity of the placental site – be it of pharmaceutical origin or related to manual interference such as fundal fiddling or cord clamping or technological interventions like ultrasound – may increase the likelihood of fetal blood entering the maternal bloodstream.  There are no guarantees though; some more recent research suggests that interventions do not always lead to fetomaternal haemorrhage and there exist women who have become isoimmunised after gentle, natural, unmedicated birth.  More in the book.

4. It was chosen by Time magazine as one of the top ten medical achievements of the 1960s…

And rightly so, as it has saved the lives of many babies.  What some people find problematic is the assumption that, because it works to prevent a serious problem that would occur in a proportion of women, there is no need to do further work to determine which women would become isoummunised without it and which women would be fine.  Given that around ninety per cent of women in the original clinical trials didn’t become isoimmunised, and that anti-D is a blood product with attendant risks, it is difficult to swallow the fact that all we can tell women is that it is not a given that they will become isoimmunised if they decline anti-D, but that research to determine who does and does not need it has never been a priority.

5. The question of who benefits from it leads to quite a mind-bending paradox..

small_2471314610Anti-D is the only product that I know (but let me know if you can think of another) that is administered to a person (the pregnant or postnatal woman) whom it does not directly physically benefit, but who has to accept the risk of possible side effects from it.  When it is given in pregnancy, it is given to the possible detriment not only of the person to whom it is administered (the woman) but also another person (the baby in utero) who does not directly benefit from it.  This is because it is given for the possible benefit of a future person or people – any children the woman may have after her current pregnancy – who do not yet exist and may never exist. Not that this negates the value of anti-D, but it’s something to ponder when you’re next looking for something to ponder…

6. The Kleihauer test is not a screening test for fetomaternal haemorrhage…

It is a screening test for larger-than-normal fetomaternal haemorrhage (where ‘normal’ in this context describes the 4ml of fetal blood whose effects will be ‘mopped up’ by the standard dose of anti-D given in most countries).  This is a really important distinction.  If a woman has a negative Kleihauer test, it does not imply that there is no fetal blood in her circulation.  (There may be no fetal blood in her circulation, but the Kleihauer test isn’t sensitive enough to tell us that and laboratory officers expect to not see fetal blood on a Kleihauer test.)  All that a negative Kleihauer test can tell us is that no fetal blood can be seen, which is taken to imply that, if there is a little fetal blood in the woman’s circulation, this is likely to be an amount whose effects can be mopped up by the standard dose of anti-D.    If the result of the Kleihauer test on a woman’s blood comes back positive and her baby is rhesus positive then she will almost certainly end up being offered additional doses of anti-D.

7. Because of this, there may be little value giving anti-D without doing a Kleihauer test…

With the exception of those extreme circumstances where people are working with no lab access or other resource issues, in which case the context of the decision is very different, I find it hard to see a justifiable argument for offering anti-D without also offering a Kleihauer test.  Although larger-than-normal bleeds are unusual, they do occur, and women need to know that giving anti-D is only half the story: we also need to offer them a test that tells us whether we have given enough.  Otherwise, we can end up with a woman who chose to have anti-D and yet has still become isoimmunised…

8. Because it is a blood product, we might want to consider affording it the same respect and precautions as we afford a blood transfusion…

Which, at least in my understanding, means appropriate monitoring of vital signs and access to immediate help and treatment should anaphylaxis ensue, which is where things get controversial again.  While I don’t want to suggest that women who have out-of-hospital births should have to leave the sanctity of their environment simply to receive anti-D, I do worry that giving this at home or in the community is potentially dangerous.  I am also concerned that this normalises the administration of a blood product which surely deserves the respect afforded to other blood products?  I am not sure there is a right or wrong answer to this but I have written more about this issue in this article and I think it is at least worth discussing at a local level.

9. We might not need to offer anti-D routinely in pregnancy if we (the health professionals who care for pregnant woman) actually followed the guidelines and offered it appropriately to women who might need it…

You can read the full argument in this article, but the core of the issue is that we know that the postnatal anti-D programme isn’t implemented effectively in all areas and the implementation of the recommendations on offering anti-D (and appropriate Kleihauer testing) is even patchier.  We know about the problem of so-called ‘silent’ sensitisation.  What we don’t know is how much of the so-called silent sensitisation is really silent, and how much of it is due to professional failure to offer anti-D according to the current guidelines.  Given that some women would prefer not to have intervention if they don’t need it, we have another situation where we desperately need more information.

Click on anti-D in the tag cloud on the right to see all information and updates relating to this topic…

photo credits: lotus flower by tarotastic via photopin  cc and question mark cat by silgeo via photopin cc