Implantation bleeding usually refers to light vaginal ... You could be experiencing a miscarriage or a medical emergency, such as an ectopic pregnancy.

An ectopic pregnancy occurs when the fertilized egg is implanted outside the uterus, most commonly in the fallopian tubes.

Symptoms of ectopic pregnancy, including abdominal pain and vaginal bleeding, are neither sensitive nor specific and are also associated with other pregnancy complications, such as miscarriage.