Ultrasound frustrations and the fears they set off

We had our ultrasound last week. We were all set to find out if we were having a boy or a girl. Well the technician refused to finish the exam because baby on certain measures measured 6 days behind and she said either my date is wrong (well unless this baby was an immaculate conception, there is no way) or it has delayed uterine growth. How can a technician make a diagnosis, why are they even allowed to do such a thing. With our oldest, they had us scared too at this same ultrasound saying the exact same thing. Anyone think maybe we just make smaller children, hello people, Nathan was born at 41 weeks weighing 6.5 pounds, you can't say that's a big baby. The doctor wasn't concerned and just wanted us to have another ultrasound done at 20 weeks, so that's what we're doing next week. Hopefully we don't get the same tech and the new one doesn't just try to scare our pants off.