First Time Mom soon asking...

The Meaning of Small Gestational Sacin Early Pregnancy The gestational sac is the fluid-filled structure that surrounds the embryo in the womb. ... Sometimes the ultrasound measurements during pregnancy will reveal a gestational sac that is smaller than expected.  In very early pregnancy, especially during a first ultrasound, a smaller-than-expected gestational sac could mean that the pregnancy is simply earlier along than you expected, based on the date of your last menstrual period. ... It's also possible that you accidentally misremembered the date of your last menstrual period.