Large gestational sac?


I had my first ultrasound today. I am measuring 8w1d however my gestational sac is measuring 9w1d. The doctor asked me to come back in two weeks to do another ultrasound. She said she wasn’t very concerned as everything else looked very healthy. I left feeling a mix of emotions..on one hand I was so excited..we just saw our babies heartbeat but on the other hand there was the concern of the large sac. Have any of you ladies every experienced this? Did your pregnancy turn out healthy?