4D scans show a sequence of movements displayed by two fetuses at 32 weeks gestation. The image shows fetal movements in a fetus whose mother is a smoker (top) and a fetus whose mother is a non-smoker (below) / Dr. Nadja Reissland, Durham University
When mothers-to-be smoke, the effects can be seen in the tiny movements of their fetuses, according to researchers examining high-resolution ultrasound scans.
Healthy fetuses start out by exploring their new limbs and body parts—touching their head and face and moving their mouth in a bunch of shapes. But these movements become less frequent as their central nervous system (which controls movement) develop.