The power of a baby's kick in the womb packs more of a punch than you would think. A recent study published in the Journal of the Royal Society Interface used MRI of fetuses and computer models to track and calculate the force of a kick and the stresses it puts on the fetal skeleton.    

"The stresses on the skeleton likely help with bone and joint formation," the researchers wrote.  

Researchers from the Imperial College of London found that the force of a fetal kick increases between 20 and 30 weeks of gestation and is important in fetal development.  

Specifically, a fetal kick's force went from 6.5 pounds (29 Newtons) at 20 weeks to 10.5 pounds (47 Newtons) at 30 weeks. However, researchers noted that the amount of force decreased at 35 weeks because the fetus has less room to move and, in this case, kick, according to the study.  

"We have quantified the biomechanics of common human fetal movements for the first time, finding increases in fetal kick forces and muscle forces, as well as stress and strain in the fetal skeleton over the second half of gestation," the researchers concluded. "We also observed concentrations of biomechanical stimuli in the fetal skeleton, suggesting a role for stress stimulation in ossification events and for strain stimuli in joint morphogenesis."