multiple fetal echos?

Hey ladies, sorry for the multiple posts, glitches I guess...

Anyhow, I am monitored due to Sjogren's with my pregnancies.  With DD I had one fetal echo (everything looked fine) and then we were able to just do NSTs and weekly dr appts from 20 weeks on.  With this LO, we had our fetal echo (again everything looked fine) but the dr at the hospital is insisting that I come in every 2 weeks until 28 weeks along (he wanted every week but I balked at that since we live an hour from the hospital, I'd have to miss work etc etc).  I am currently seeing my obgyn every week for a heartbeat check and they said that if heart blockage were to occur during the next 5 or 6 weeks, that they could detect it from the doppler...

I guess better safe than sorry, but now I am wondering why the hospital is insisting on the extra fetal echos... especially since I just had my DD's fetal echo less than a year ago and although they mentioned more appts, they did not push it.  Does anyone else have to have multiple echos?  Did they give you a reason? Just curious.  Thanks!