No information is available on the clinical use of coagulation factor Xa during breastfeeding. Because it is a large protein molecule with a molecular weight of about 40,000, the amount in milk is likely to be very low and absorption is unlikely because it is probably destroyed in the infant's gastrointestinal tract. Until more data become available, coagulation factor X should be used with caution during breastfeeding, especially while nursing a newborn or preterm infant.