How accurate are Doppler Studies?

[caryn]

They can depend on the skill of the ultrasound tech *and* they can change as pregnancy progresses. Placentas are dynamic - if they "notice" that they are short of blood there are a number of strategies they can adopt to affect bloodflow - and sometimes will dig in more deeply, so we have had posters outgrow some UA notching.

That said, I don't remember seeing it happen at this later stage of pregnancy. Most often someone will have a worrisome scan at 20 weeks and have a better scan at 28 weeks.

[mommy2maddie]

So at 29 weeks 4 days I saw my MFM for the first time during this pregnancy, I was told blood flow to the baby was not good. After further talking with my regular OB, he explained to me that my placenta was working harder to supply the blood to the baby because there was resistance in the cord but that it was never absent or reverse. He said the pressure(i think this is what they call it?) in the cord at that doppler study was 93% which was high. I went back to the MFM at 30 weeks 4 days for another doppler study and the pressure in the cord was 74%, which I was told was high end normal, and they said it must be because I have been on bedrest since my last appt. I just recently went back to the MFM at 32 weeks, this past monday, and blood flow was found to be completely normal, their words. So my question is how accurate are doppler studies? It seems there is an awful lot of variation going on here. Could the first doppler study that found the bad blood flow at 93% be a fluke? Are their certain factors that can make this change so quickly? I feel so confused I went from being told at 29 weeks that I could deliver at any point and be prepared for it and now I am being told I could possibly make it to 39 weeks! It is sooooo frustrating!