What could be the reason to repeat the anatomy scan?

Hello doctor,

I went in for my anatomy scan at 18 weeks. The scan lasted about 30 minutes. All seemed to look great and the ultrasound tech seemed to be very positive. She commented some on the baby moving but never commented on it hard getting photos due to the movement. She took about 85 images total for the Radiologist to review.

We were able to see every part of the baby and even were amazed when it came to her heart that you could see all four chambers. We left very positive and excited. Two hours later I received a call from my doctor's office stating the results came back and looked fine however there was suboptimal evaluation of fetal heart, spine, and kidneys. My doctor told me I would need to go back in for an ultrasound in two weeks. I am worried to death that there is something wrong. My doctor made it sound like no big deal but I have been an emotional mess since hearing the news. My questions are as follows...

1. Is this normal and happens frequently, especially with a scan at 18 weeks?

2. What does suboptimal evaluation mean? If the picture was blurry or not of good quality would they not say suboptimal visualization?

3. We have heard the baby's heart many times and her heartbeat is consistently around 142 beats per minute. We even have a fetal monitor and have always heard a strong beat, no murmurs or concerns. What are the signs if something were wrong with her heart?

4. If the problem came down to poor imagery, why did not my doctor just say that? Could they be keeping a larger problem from me?

5. If the radiologist saw something of concern would they say, a problem with the heart needs to come back in for re-evaluation or suggest seeing a specialist?

Any of your suggestions and reassurance would be much appreciated. Thank you so much.