Does Quora/Google eavesdrop on conversations?

A couple of weeks ago I visited a hospital and was advised by the doctor to take an ultrasound test. After 1–2 days, I started seeing questions related to “ultrasound” on Quora. Was it a pure coincidence or is there a logical explanation for this?

More information:
1. I use my Google account to sign-in to Quora
2. I haven’t searched on Google about ultrasound.
3. Only context in which I used the term “ultrasound” are as follows:
– In-person conversation with a friend who accompanied me to the hospital
– Bill from the hospital
– In-person conversation with a few friends