Right
When a weeks-old fetus sucks its thumb, hand preference may in the making.
Scientists who studied ultrasound scans of 1,000 fetuses and followed the progress of some of these babies after birth, found that if a fetus preferred to suck its right thumb more than its left at just 10 to 12 weeks gestational age, the child tended to be right-handed after birth, reports New Scientist magazine of research at Queen's University in Belfast, Northern Ireland.