Special care should be taken when women with preeclampsia are considered for blood transfusion postpartum because of the increased risk for transfusion reactions, Swedish researchers say

Their study also found that postpartum haemorrhages that require blood transfusion are becoming more common.

Published in Blood Advances the study found that in 517, 854 women who had pregnancies reported between 1990 and 2011 in Stockholm, 12,183 (2.4%) women received a blood transfusion.

There were 96 events involving a transfusion reaction postpartum, giving a prevalence of 79/10, 000 compared with 40/10, 000 among nonpregnant women (Odds Ratio 2.0).

The study showed that preeclampsia was the single most important risk factor for transfusion reaction (OR 2.1).

Previous caesarean delivery also heightened the risk of placental complications and bleeding in subsequent pregnancies. In this study, 26 % of all women who received more than 10 units of blood postpartum had a previous caesarean delivery compared with 8% of women who had no blood transfusion postpartum.

The likelihood of problems was also significantly increased when a combination of all three types of blood component (red blood cells, plasma and platelets) was administered.

The researchers from the Karolinska University Hospital, also found that the number of postpartum transfusions increased by 40% during the 20-year study period.  The exact reason for this was not clear but the investigators said it may be due to the trend for pregnant women to be older, have higher body fat, more often conceive by IVF, and more likely to undergo caesarean delivery, have placental complications or multiple pregnancies – all of which are thought to be contributing factors.

“There seems to be something about pregnancy that makes transfusion-related adverse events and complications more likely,” said Dr Lars Thurn (PhD) of Karolinska Institutet in Stockholm, Sweden, and the study’s senior author.

“Based on our findings, obstetricians and clinicians need to be more aware of these potentially harmful reactions when evaluating pregnant women for blood transfusion, especially if they have preeclampsia, induced labour, or preterm delivery.”

“In this population blood products should only be administered when necessary and when alternative options have been considered.”