Final answer:
A complication of an external version is indicated by fetal bradycardia persisting 10 minutes after the procedure, as it can reflect a serious reduction in oxygenated blood flow to the fetus.
Step-by-step explanation:
The event that indicates a complication of an external version is b. Fetal bradycardia persisting 10 minutes after the version. An external version is a procedure used to turn a fetus from a breech position into a head-down position before labor begins. Complications can arise during or after this procedure, one of which is fetal bradycardia, a slower than normal heart rate in the fetus. Prolonged bradycardia can indicate fetal distress, as it reflects a reduction in oxygenated blood flow to the fetus, often due to severe or lengthy contractions. This can lead to the need for an emergency birth, which might be assisted with vacuum, forceps, or a Caesarian section.