they were checking mine via u/s weekly when they discovered that I had funneling issues but they stopped doing that at 30 wks for me then they said they were only going to check if I was symptomatic and I am a dew days shy of 37 wks and I am assuming they are going check me at my next apt this week cause I have been having a lot of cramping and stabbing pains down below.
Most dr's will start doing them around 35 weeks. But every doc is different.