Indigo:
 The placenta doesn't move *at all* from the place it implants - however, it
can APPEAR to be higher later in the pregnancy than it looks early on (and this
is exceedingly common).  AS the uterus grows, the placenta's true placement
becomes easier to see.
 example: take a balloon and make a pen mark near the neck of the
balloon....then blow the balloon up.  What once looked close to the neck often
is 1/4 of the way up the side of the balloon once it's fully inflated.  Same
thing as the placenta "migrating".  It doesn't move...the uterus just grows and
stretches and the true placement is seen.
 So long as there isn't any part actually OVER the cervix...you're fine.  And
if it can be seen that there isn't any part over the cervix, there will never
be...as it doesn't move from where it's firmly attached to the uterus.

 On another note...a low placenta is not a placenta previa.  Low placentas are
of no consequence whatsoever.  A placenta previa is an issue...but that means
that at least part of the placenta actually COVERS the cervix.  How far along
were you at this last ultrasound? And how far were you for the first one?

 Tubes:
 I would definately request/order a copy of my records from the hospital as
well as my doctor and review them.  That shoudl put to rest any questions you
have...

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