I think at first trimester the baby is still small so from ultrasound the gynae can't really tell if baby length is the full length so it's just an estimation. I'm at second trimester now and previously during my first few appointments, baby seemed really small sized as well. Stay positive and worry less all the best!
The ultrasound is just gauge and not exact. Even at 3rd trim the display shows diff “measurement”. As long as gynae did not highlight anything means its fine! As long as baby still has a heartbeat and not stuck at the exact same “measurement”
It’s normal. The measurements are not 100% accurate and also depends on baby angle. Don’t worry too much about it - there’s a margin of error on ultrasounds. If you’re worried, you can ask your gynae about it.
If your gynae didn't say anything about the growth being slow then you shouldn't worry either. Don't put unnecessary stress on yourself
scan is only a best estimate... my calc & the scan has always been a couple of days off but as as gynae didnt raise any red flag 💕