I don't know about research on molding, but it seems unlikely to me that this would be an issue.

Further, ultrasound measurements are NOTORIOUSLY inaccurate.  I had a client a year ago planning a VBAC who was told at her 40 week ultrasound that the baby was 10 lbs.  That day.  Not "predicted to be 10 lbs in a week."

She spent a week of MUCH stress arguing with her OB about laboring or not...

Baby was born at 41 weeks 1 day and weighed 8 lbs 12 oz.  No sign that he had lost weight due to placental insufficiency or anything like that.

Further, there is no way to really tell when you will spontaneously go into labor.  You can be tight as a drum one day, and holding your baby the next, or dialated to 3 cm/50% effaced for weeks.

Good luck!

Jenn