Hi OP - lots of 
because I remember how stressful it is!
My story (spoiler - it ends well!):
DS2 measured small (on a scan I was having for a different reason at about 30 weeks), just under the 10th centile, and I was moved to consultant pathway. I had ultrasound scans for fluid volume and Dopplers every 2 weeks until term, and everything was always fine.
But I was very suspicious of the chart that put DS2 below the 10th centile because his projected birth weight on his centile line was fine (about 3.2 kg). Turns out that because I was tall (I'm 5'11), it was factored into DS2's custom fetal growth chart and led them to expect a giant baby. DS1 wasn't giant, but they were usin a different non-custom chart back then, so hadn't been concerned.
I had a good long chat with the head consultant about the poor diagnostic value of including maternal height in fetal growth charts (I'm a scientist/statistician, so read the journal papers and could talk the talk), and he was fairly pragmatic and said he thought it was a healthy but small baby rather than IUGR. More to the point, he was happy to go along with my preference for a "watch and wait" approach until 40 weeks, so long as scans and dopplers looked good, rather than induce at 38-39 weeks (as another consultant on his team had tried to push me into).
I went into labour naturally at 40+1, had DS2 in the labour ward with just a midwife and DP in attendance (though the paediatric swat team was outside the door)... and he wasn't small at all. He was just over 3.5 kg, which I think was between 15th and 20th centile in the custom chart.
At that point, my consultant had agreed that we could go to 41 weeks on "watch and wait" but then we should induce. I was sure DS2 would arrive before then so agreed in principle... but was glad it wasn't necessary!