“When Phoebe’s little legs are tucked under her body, I see how she was able to fit into the tiny space of the womb. At first I was concerned because I didn’t know why her legs were positioned like that.”
Babies born at gestational term have a tightness to their bodies called physiological flexion. Space was limited in the final trimester and the baby assumed the most compact position with arms and legs held close to her core. Physiological flexion provides some passive stability for the newborn baby to use for function. Practice will provide an opportunity to decrease muscle tightness through active movement. In turn, active movement provides sensory input and postural control. Development happens gradually, month by month with one skill building upon another. The posts in the milestones category describe the maturation of babies in the first year of life as they begin tightly flexed and learn to roll, sit, cruise and stand.
Phoebe, at eight days of age, is laying on her back with gravity acting on her spine, which is naturally in a slight c-shape curve from the thoracic region all the way to her sacrum. Her shoulders are often elevated and protracted with upper arms (humeri) held in internal rotation. Gravity is making this less noticeable while she is on her back. At this moment she is stretching out her arms with wide random movements and her legs are intermittently kicking. Her pelvis is regularly held in a posterior pelvic tilt. Her hips are held in flexion, abduction and external rotation. Her knees are in flexion and her ankles are in dorsiflexion and inversion.
Phoebe’s skeleton will develop as a result of active movement. She has a neonatal position of the spine, rib cage, pelvis, hips and foot bones. Action of the muscles over the next year will shape the bones into more mature positions.
As you can see, although Phoebe looks like she is just taking a rest on her back, she is doing the hard work of changing from a newborn to a one-month old.