You Can Donate Blood Before Pregnancy and While Breastfeeding

February, Black History Month, is a good time to take a new look at blood donation issues surrounding pregnancy, which we last covered 4.5 years ago. One century ago, Charles R. Drew, an African American teen in Washington, DC was gearing up to attend Amherst College, where he would excel in just about everything, academically and also in sports. Hoping to become a doctor, the doors were largely closed to him in the United States of the Jim Crow era, but he gained medical school admission across the Canadian border, at McGill University in Montreal, Quebec. Returning to Washington, DC in the mid 1930s with both Doctor of Medicine and Master of Surgery degrees, he joined the Howard University pathology department and the surgery department at Freedman’s Hospital, and spearheaded blood research that he had begun in Montreal. Although doctors knew, from research by Karl Landsteiner at the turn of the century, that blood donors and recipients had to be matched by blood type, blood donation in the mid 1930s was very slow, inefficient, and could be dangerous. Either blood was transfused directly from the donor to the recipient or collected from the donor into a bottle and infused into the recipient after very short periods of time. In the bottle, or other container, such as a bag, the blood could begin clotting. To solve the clotting problem, scientists during the First World War had learned that adding certain chemicals could prevent clotting, so it was possible to preserve blood, but not for very long periods of time. With yet another world war brewing in Europe, the available, crude methods would not be adequate for dealing with blood loss, but in 1938, Drew moved to New York to begin a PhD program at Columbia University, specifically in blood science. In the course of his graduate research, World War II erupted in Europe.

In 1940, the US was not yet in the war, but Great Britain was in need of blood and Dr. Drew was now the world’s leading expert on blood banking. In the course of his research, he developed techniques for separating blood into its plasma (liquid with proteins) and cellular (containing cells along with cell fragments called platelets) components and for storing those components separately. This enabled a blood donation, preservation, and banking process so efficient that blood could be collected in the US, flown to Great Britain and used to treat British military personnel and civilians wounded in German bombings of London and other parts of Great Britain. When the Japanese attack on Pearl Harbor brought the US into the war at the end of 1941, Drew was called to scale up his British blood banking process into an American national blood bank. He did this, but then the US military insisted into segregating donating blood into Black and Caucasian products, each to be used only in recipients matching the race of the donor. This racist policy ran so contrary to the science, which had revealed that blood types were independent of racial characteristics, that Drew threw up his hands and returned to Howard University. For the next decade, he continued advancing the science of blood banking until 1950, when he was killed tragically in an automobile accident at the age 45.

Standing on Drew’s shoulders, researchers have advanced blood banking by leaps and bounds  over the past three quarters of a century, but you still cannot donate blood when you are pregnant, even though you actually have more blood in your body by late pregnancy than at any other time. You even have more blood cells than normally. However, your blood is more dilute than usual, because pregnancy increases the blood volume, while not increasing the number and volume of blood cells enough to keep up with the increase in blood volume overall. And so, pregnant women tend to develop mild iron deficiency anemia. Even when not pregnant, a woman may not donate blood if her hemoglobin concentration is less than 12.5g/dL, while a male must have a hemoglobin concentration of at least 13.0g/dL to be a donor. Various other factors can disqualify people from donating blood, including having hemoglobin concentrations that are far too high (in which case something is wrong with the blood).

In addition to the need to protect pregnant women and their fetuses, there is an additional reason why pregnant women are not supposed to donate blood, and especially plasma. This applies to those women who have been pregnant multiple times and relates to a rare but serious complication that recipients of blood products may suffer. Known as transfusion-related acute lung injury (TRALI), this complication develops within six hours of transfusion. Scientists and transfusion doctors think that TRALI results from an immune system reaction affecting the lungs that may involve antibodies present in donated plasma. This would make the process similar to what doctors called Rh incompatibility, the pregnancy complication that occurs when a mother with Rh-negative blood is exposed to Rh-positive blood from a first fetus, and then is exposed again because of a second Rh positive fetus, when her immune system reacts more strongly. In Rh incompatibility, the problem can be prevented by giving the mother an antibody called RhoGAM. In the case of TRALI, however, prevention is not as simple as administering an antibody drug. On the other hand, red blood cells (RBCs) themselves, without the plasma (transfused as as what doctors call packed RBCs [pRBCs]), are not thought to pose anything like the risk that plasma poses. Today, thanks to a process begun nearly a century ago by Charles Drew, transfusion patients are given mostly individual blood components, whether pRBCs, platelets, plasma, or various other blood components or fluids. Rarely are people given whole blood, other than in certain trauma situations.

When not pregnant, women lose blood every month due to menstruation, but plenty of women are able to donate blood (they have enough hemoglobin and enough red blood cells, despite the menstrual blood loss) to be donors. This includes women who are preparing to become pregnant. Studies show that women who donate blood or plasma regularly before becoming pregnant are not at elevated risk of medical problems during pregnancy, or of problems for the baby. This is true as long as they do not become anemic from donating, but anyone who is becoming anemic will not be allowed to donate more blood anyway, until her numbers are back to normal.

So you can donate blood prior to pregnancy, if you meet qualifications, but what about subsequent to giving birth, for instance while you are nursing? The answer to this is actually yes, also, of course, if you meet qualifications. The American Red Cross allows breastfeeding women to donate blood as soon as six weeks after giving birth, provided that their numbers are good, they are not anemic, either based on hemoglobin or the concentration of red blood cells, or the size of the red blood cells. Meanwhile, the World Health Organization takes a somewhat more conservative view, suggesting that blood donation is safe, but recommends that women wait until three months after the child is weaned, or “mostly weaned.”

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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