aHUS in pregnancy and after

Article No 410

13 January 2021

The link between pregnancy and aHUS has been known for several decades. A chapter was devoted to it in Prof. Bernard Kaplan’s book about HUS and TTP in 1992 ( There was even a chapter about the Birth Control Pill too!).

In the last decade, probably with the advent of eculizumab and more genetic knowledge, pregancy aHUS is seen less as a secondary aHUS and more of a primary complement mediated aHUS. The advent of eculizumab has also widened the scope of interest on its use during pregnancy.

Another emerging issue is the diagnosis challenge within a spectrum of other thrombotic microangiopathies ,TMAs, that pregancy can trigger.

There is now even an   International Working Group on Pregnancy-Related Thrombotic Microangiopathy (TMA)  with the some of the leading experts in this field participating.

Among them is Prof. Fadi Fakhouri of Lusanne University Switzerland. Prof Fahouri, who has featured frequently in this websiteb, is probably THE lead expert for pregnancy aHUS .

Professor Fadi Fakhouri

He appeared in the inaugural ERKNet training webinar of 2021 to talk about “Pregnancy related TMA” . A recording of his talk can be seen by registering at this link HERE

A synopsis of key points in his talk follows:

80% of the webinar audience had seen less than 5 cases of pregnancy TMA in their careers. Only 4% had seen 10 or more cases. This showed how rare this conditiion is.

Most pregnancy aHUS occurs post partum.

It can happen in any pregnacy a woman may have.

Many women experiencing aHUS have a complement mediated susceptibility. Hence the reclassification to a Primary aHUS .

There is now evidence that higher eculizumab doses, or shorter intervals btween doses, may be needed to control aHUS during pregnancy.

Diagnosing aHUS in pregancy,  71% of the audience said that it is done by excluding all the other causes of TMA in pregnancy. There is no relaible blood test just for aHUS.

The international working group has devised an algoirythm to diagnose the cause of a pregnancy TMA. The more common cause of TMA is eclampsia/pre eclampsia but aHUS can be differentiated from it by a number of factors and those have been listed by the working group. ( An abstract of the group’s publication can be seen HERE)

The Working Group has also created a treatment algorythm. This included eculizumab for aHUS,  and also when it could be withdrawn.

Withdrawal is possible but when that happens depends on the characteristics of patients.

Pregnancy is not contra-indicated for a women with, or susceptible to, aHUS but it needs to be recognised as a high risk pregnancy.

There is no experience of ravulizumab use in pregnancy.

Prof Fakhouri confirmed that the working group did not advocate prophylactic use of eculizumab in a known aHUS pregnancy.  Close monitoring and rapid treatment with onset is both clinically and cost effective.

Breast feeding on eculizumab is NOT contra-indicated.

Recurrence of TMA in pregnancy after a period of aHUS remission would be treated rapidly with eculizumab.

Prof Fakhouri did not suggest switching  a patient already on ravulizumab to eculizumab should the patient become pregnant.

Testing of other aHUS family members who could become pregnant was not considered needed by the International Working Group. But if it is available no harm in knowing.

No evidence yet of anti eculizumab neutralising antibodies.

There was so much interest in this subject from the clinical audience that there were so very many questions that the webinar moderator decided to stop any more from being asked as the webinar would overun.

Again more insights about pregnancy and aHUS, thanks to the work that Prof. Fahkouri does.

The next aHUS specific ERKNet webinar is on 1 June with Marina Norris as the speaker