When adults cut themselves, a multi-step process called hemostasis stops the bleeding from the injured blood vessel. But hemostasis in infants is different from hemostasis in adults. This difference can be problematic if infants require surgery to address significant medical problems. In surgeries, patients normally receive blood from adult donors to compensate for blood lost during the operation.

“But if you give adult blood to an infant, the difference in adult hemostasis versus infant hemostasis can lead to too much clotting,” says Ashley Brown, co-corresponding author of a paper on the work. “That can increase the likelihood of thrombosis, where blood clots form in the lungs or elsewhere and put the baby at risk.