amniotic sludge

Has any one had sludge in pregnancy? I’m 16 weeks pregnant, I’ve a pre pregnancy tac in place this is my second pregnancy from I’ve had it placed the first one was smooth no problems, I’ve had 2 pre term losses prior to getting my tac placed & have just been told I’ve sludge in my amniotic fluid, I’m on antibiotics and have appointments every two weeks, my cervical length is perfect and no openings in my cervix so they don’t seem concerned. My only concern is my labours have always been spontaneous they come on very fast and the second time there was no warning signs.. I’m terrified & would love to hear if any one has had this before?