Acquired thrombophilias are tendencies to clot that develop in adulthood or older age, and are not inherited.
Phospholipid antibodies are an example of acquired thrombophilias.
Genetic thrombophilias involve any of a number of genes that disrupt the ability to break down blood clots. The balance between bleeding and clotting is much more delicate in pregnancy than at most other times in life due to dramatic changes in blood vessel flow and blood vessel structure. The placental cells grow into the uterine blood vessels and destroy their linings and muscle layers and create basically a free flow, pressure passive system. The balance between bleeding and clotting is generally more tenuous in this system and any inefficiency can then push that delicate balance in favor of clotting. As a reproductive pathologist I look for clots that could cause a pregnancy to fail and take special note of where they occurred in order to see whether an appropriate course of treatment can be determined or if further testing is required.