9 things you might not know about Anti-D…

Over the years, I’ve become aware that there are a few things that people are sometimes surprised to learn when I speak about Anti-D. I made sure to include all of these and more when I recently updated my book on Anti-D. But I’m sharing the most important ones here as well.

If you’re completely new to this area, you might want to start by reading the Anti-D resources series. And if you’d like more information on any of this, do have a look at my upcoming book, Anti-D Explained. It’s due out in June 2021.


1. It’s made from blood…

Actually, most of the people who need to give Anti-D or consider whether they want to receive Anti-D do know this now. Not all, but most.

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.

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. That 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 everyone has 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. I am sometimes 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

And what’s most important to me is that everyone has good information and makes the decision that’s right for them.

The issue is that the research shows 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 showed, around one in eight rhesus negative women who have given birth to a rhesus positive baby will become isoimmunised if they do not have Anti-D. The other seven out of that eight didn’t become isoimmunised. Unfortunately, we don’t have much information about who is more or less likely to need it. And we don’t know as much as we might like to about the risks, especially when it is given in pregnancy. But isoimmunisation is permanent, so these are big decisions. 

Our lack of knowledge about some aspects of Anti-D is because of the decisions made following the original clinical trials on this (which you can read about in my book or in this article). So it’s important to get all the facts before making 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. 

There is a theory 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 bleeding. And there absolutely exist women who have become isoimmunised after gentle, natural, unmedicated birth. 

More on this in my 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 helped many babies. Although improvements in neonatal care have played an important role as well.

What some people find problematic is the assumption that, because Anti-D 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. 

Many of the women in the original clinical trials didn’t become isoimmunised. And Anti-D is a blood product with attendant risks. So it is frustrating that we don’t have more research. All we can tell women is that it is not a given that they will become isoimmunised if they decline Anti-D. And that research to determine who does and does not need it has never been a priority. Neither had research been carried out into alternatives.


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

Anti-D is the only drug/medicine that I know (but let me know if you can think of another) where the following things are true:

It 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. And ‘normal’ in this context describes the 4ml of fetal blood whose effects will be cleared 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. Scientific 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. This 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 cleared by a standard dose of Anti-D.

If a Kleihauer test is positive and a woman’s baby is rhesus positive then she will almost certainly end up being offered additional doses of Anti-D. That’s in order to clear the additional fetal blood that is in her circulation.


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

Some people in rural areas work with no lab access or have other resource issues. In that situation, they may have no choice but the offer Anti-D without Kleihauer testing. In all other situations where Anti-D is given because there has been a potentially sensitising event, a Kleihauer test should also be offered.

Although larger-than-normal bleeds are unusual, they do occur. 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 chooses to have Anti-D and yet has still become isoimmunised.


8. Because Anti-D is made from blood, it should be afforded the same respect and precautions that we afford a blood transfusion…

This means appropriate monitoring of vital signs. It also means access to immediate help and treatment should anaphylaxis ensue. This is where things get controversial again. I don’t want women who have out-of-hospital births to have to leave the sanctity of their environment simply to receive Anti-D. But in many areas it is not given at home or in the community is potentially dangerous. There is also an argument that this normalises the administration of a blood product. 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. 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. (I’ve discussed that in this post, and in more depth in my book).

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.


If you’d like to know more about Anti-D, my book is called Anti-D Explained. It has been written to help women and families understand the issues and the evidence. It will be published in June 2021.
And if you’d like me to keep you updated with birth-related research, click here to sign up for my free monthly newsletter containing research, blog posts and other updates from me.