10 Week Ultrasound Question!

Kay

This was my sonogram from the doctors office at about 10 weeks.. it was transvaginal ultrasound. Does anyone know or understand why the black area seems so large around my baby and what would the white space in the middle be? Baby was measuring the way he/she should and we saw the heart fluttering.. doctor didn’t speak of any concerns but now I’m curious because I don’t remember seeing it like this for my first