sparkles, please don't stress. as the other ladies said, there could be any number of reasons - foremost being human error.

at my first ultrasound Jelly was measuring about five days under her due date. by the time i had my next u/s she was measuring about 5 days larger then she should have been. my ob said both times just to ignore the measurements as they are often inaccurate, and are only indications, not absolutes. i haven't had another u/s, but my fundal height is measuring larger then i should for my dates, and yet my ob said that my baby will most likely be of average size when its born.