Hi There I'm 34 Weeks Tomorrow, Baby Girl, First Pregnancy,

Hi there I'm 34 weeks tomorrow, baby girl, first pregnancy, I've been seen basically weekly since 20 weeks where I was diagnosed previa but also had maternal blood work come back positive for SB
Turned out baby is healthy and it was the previa that through off the blood work... No spina bifida, everything else came back neg for downs etc...
At first baby girl was a week behind in measurements, then a couple weeks behind symmetrical, then to 3 weeks behind where she's slightly asymmetrical, she has been less than 5th percentile the whole time and is following her own little curve... They plan on delivering her via scheduled c section by 36 weeks...
Any thoughts? Have you seen a case like this before??
For a little while the dopplers showed slightly increased resistance,, but now they seemed to have improved.
I've read that shortened femurs could be a sign of DS, but my docs just think I have a small or crappy placenta, any input will help.
Thanks for your time!!!