I'm a total mess and need help understanding what this can p

Since week 21 I have been geting regular ultrasounds not being explain why. the first ultrasound I got the tecnician asked me if any of my children were born with abnormalities to which I said no but I do have a baby who is developmentally delay among other issues. A week later I recieve another ultra sound to be given an apoitment for a biophysical and growth ultrasound. me puting things together as to the tecnician question and having this other ultrasounds which are usually performed once you pass your due date i am very concern. why would a biophysical ultra sound be requested before i am into my third trimester, not even pass my due date as well as a growth ultrasound if nothing is wrong. as far as i'm concern the doctor keep telling me not to worry and does not probide me with any information, even if is just a suspicion which is very upseting! I was also looking at the pictures of my 23 week 3 days ultrasound and the baby is measuring 16.8 cm and was wondering if this is normal lenght for a fetus that age. The ultrasound picture also says tib/fib low and was very curious as to what this can possibly means in a fetus? I try to research like there is no tomorrow over the internet as to what can bring me some peace of mind with no luck. I am desperate here and asking for someone that may know what all these things means. I am so frustrated and scare because the doctors are not telling me anything and my mind is flying everywere. thank you in advance and sorry for the long post.  

Those measurements are not your baby nor is the tib flow whatever. Its the settings of the u/s machine. I had tons of weird ultrasounds to track growth and everything. In the end, baby was ok. Its just a precaution it seems like but ask your ob at ur next appt for further reassurance.

I do have to say, I have a baby that is developmentally delay and among other issues she has chromosomal abnormalities in two of her chromosomes. I was already expecting this baby when the genetic doctor performed the same test on my daughter that showed these chromosomal issues to find out i have the same chromosomal abnormalities and my fear is that this is affecting the baby too. I would love the baby no matter what but scare.

Right i mean that is only normal. However, the things you see on the top and sides of ur u/s pics are not pertained to ur baby. It's just the settings of that particular machine. They thought my son had down syndrome and after doing multiple tests and ultrasounds, he is fine. Just bring your concerns to your ob and im sure they will enlighten you as much as possible on your situation and make you feel better about it.

Thank you for your advice. i am just nevous and scare out of my mind because there has to be a reason why they ordering a biophysical and growth ultrasound when I am only 25 weeks along. Not sure why but my feelings are they have some sort of concern. I wish they would tell me what it is...