Low Papp-a value

I'm expecting twins and we did the first trimester screening, NT came back normal. We did the MaternIT21 as I have a son with a genetic disorder and everything came back normal on that(at least one is a boy). Today our genetic counselor called and said the bloodwork from the finger prick came back and my Papp-a value is a little low 0.5 and that they're gonna do high value ultrasound, which they were gonna do anyway because of multiples. I'm extremely nervous now as my first pregnancy was twins from an IUI and we lost one at 30 weeks due to IUGR. Has anyone else had low Papp-a value? Did your dr offer any suggestions of things you can do to help growth?