The strength of a baby’s kick while in the womb grows stronger over time, peaking at midway through the second trimester, new research shows. This movement aids in the development of bones and muscles, much like exercise helps in adults.
While the strength of the kicks drops after 30 weeks, in large part because there is less room to move around, the development continues because the baby’s legs are now meeting more resistance. But even those weaker kicks are helping to strengthen the baby’s leg muscles.
A team of bioengineers from the Imperial College of London said few studies have ever looked at the forces involved in kicking and the effects on musculoskeletal development in the womb. Their results were published in the journal Interface.
The team used cine [sin-E] magnetic resonance imaging, a technique that shows multiple single images over time, to create a video of the babies’ movements. They tracked hip, knee and ankle joint actions when the baby kicked. The researchers then built computer simulations based on the videos that allowed them to determine the strength of the kick and how that movement affected the baby’s skeleton.
They measured the strength of kicks at 20, 25, 30 and 35 weeks. Between 20 and 30 weeks, there was a significant surge in strength of kicks, from 6.5 pounds to 10.5 pounds of force. From weeks 30 and 35, the intensity of the kicks significantly fell, to 3.8 pounds of force.
The researchers hope their findings might help doctors diagnose and treat conditions that can affect skeletal development in the womb — specifically in medical conditions in which reduced movements play a role.