Although things such as fetal distress during delivery, emergency cesarean delivery (commonly referred to as a C-section), and traumatic injuries can cause infant and childhood strokes, a major contributor is congenital malformations or conditions that affect blood clotting.
Some of these problems may be known through family history or genetic testing, but there's really no way to prevent most genetic or congenital disorders that can cause a fetal stroke. In rare cases where a bleeding disorder is the cause of a stroke in an infant, vitamin K administration can help.
While this is a standard supplement given at birth in most areas of the United States, increased brain hemorrhages in infants have been noted in parts of the world where vitamin K is not offered at birth or when parents refuse.
Drug use or even the use of certain prescription medications during pregnancy can also contribute to clotting or bleeding disorders.