A Perinatologist's Perspective:

The nuchal translucency (NT) exam at 11-14 weeks and the detailed is an absolutely critical exam.  It not only provides early information about the health of the pregnancy, but also accurately dates the pregnancy - and while many people are sure of their due date before the NT exam, statistics show that about 60% of women do not get their conception date correct (and thus their due date).   It may not seem like an important matter at 12 weeks, but having a due date off by 5-7 days 28 weeks into the future could be critical to the timing of your delivery and health of your baby.