Paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS), or hemolysis, elevated liver enzymes, and low platelet (HELLP) syndrome can be triggered by pregnancy. Due to the possibility of serious complications, pregnancy is somewhat discouraged in the presence of these disorders.

Eculizumab is a humanized monoclonal antibody that acts by blocking the enzymatic cleavage of complement C5 to C5a and C5b. It has been used for the treatment of PNH and aHUS, as it decreases the need for blood transfusion and improves quality of life and overall survival. However, the use of eculizumab during pregnancy has not been extensively studied.

A review paper published in the Journal of Nephrology gives an overview of the current available literature on eculizumab in pregnant women with PNH, aHUS, and HELLP syndrome. Linda Sarno, MD, of the department of neuroscience, reproductive sciences, and dentistry at the University of Naples Federico II in Italy, and colleagues evaluated the use of eculizumab for PNH, aHUS, and HELLP syndrome in pregnant women.

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The researchers also looked at data on the potential passage of eculizumab or eculizumab–C5 complex (E–C5) across the human placenta and its effects on the complement system of newborns. The available literature, although limited, suggests that eculizumab neither passes into breast milk nor reaches high concentrations in cord blood. No adverse effects of eculizumab on complement levels have been reported, but larger case series, noted the authors, are required to confirm these findings.

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Arpan Patel, MD, from the division of hematology and oncology at the University of Florida College of Medicine in Gainesville, noted that his own work has shown that eculizumab appears safe for pregnancy and specifically for the mother. “We have not done any testing for the fetus and infants, but it appears that it is safe in newborns based on current data. However, samples are limited,” said Dr. Patel. “Therefore it is not safe to say that eculizumab can be used in pregnancy [without affecting] the fetus — but it is safe to say that this drug, according to the current literature, appears to be usable in the fetus.”


PNH is a rare bone marrow failure disorder that manifests with hemolytic anemia, thrombosis, and peripheral blood cytopenias. It can be life threatening for both the mother and the fetus, as pregnant women with PNH have a higher risk for thrombosis and hemorrhage.

There have not yet been any reports of maternal use of eculizumab leading to fetal malformations or developmental disorders. One survey reported a preterm delivery rate of 29%, primarily due to preeclampsia, intrauterine growth restriction, and thrombocytopenia. Complications observed in the neonates included transient neutropenia (one case) and slightly delayed speech (one case), but it cannot be ascertained if these events were related to eculizumab or to prematurity.

The authors also point out that there was great variation in time of eculizumab initiation, dosage, infusion intervals, and duration of therapy. For example, in some cases eculizumab was begun at conception while in others it was initiated towards the end of pregnancy, at 30 weeks of gestation.