Hypotonia is a medical word for low muscle tone. If your baby has it, they will likely feel limp in your arms, like a rag doll. That’s why it’s also called floppy infant syndrome. Doctors can diagnose the condition in the first few minutes of life. They do routine checks of newborns’ muscle tone at 1 minute and 5 minutes after birth. Sometimes hypotonia shows up a bit later, but it will usually be noticeable by 6 months of age. Poor muscle tone tends to signal a problem with the brain, spinal cord, nerves, or muscles. But physical therapy and other treatments can help your child build stronger muscles and better coordination. Symptoms Most babies enter the world with good muscle tone. It lets them flex and flail their little limbs. Newborns with hypotonia won’t have strong arm and leg movements. As they get older, “floppy” babies will miss important milestones, like being able to lift their heads when they’re on their tummies. Other common symptoms include: Poor head control. When...