There are lots of companies advertising scans and videos of your baby in the womb, is it safe to have one?
Ultrasound scanning in pregnancy began 40 years ago and the majority of valid research 1 would indicate that scans are safe including when increased scans are clinically indicated. Currently in the UK women will be routinely offered two ultrasound scans as part of the NICE guidelines for routine antenatal care (2). Further scans may be clinically indicated in the 3rd trimester but will be arranged on an individual basis, all of these scans will be 2D.
As you indicate in your question there are many companies now offering 3D scans (still pictures) and 4D scans (moving picture copied onto video or DVD), the main consideration is the expertise of the person carrying out the scan. Another factor to be aware of is the pathway for referral to an appropriate consultant obstetrician if anything untoward is discovered on your scan, not all companies employ the services of obstetricians or midwives.
1.Duck F Safety Aspects of the use of ultrasound in pregnancy, Fetal and Maternal Medicine Review. (2003), 14: 1-21 Cambridge University Press
2 NICE Antenatal Care: routine care for the healthy pregnant woman RCOG 2003