A fetus at 12 weeks can make a fist and suck its thumb.
Update Date 9/26/2015
Updated by: Daniel N. Sacks MD, FACOG, obstetrics & gynecology in private practice, West Palm Beach, FL. Review Provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.