A position that is held by engaging the core and bringing the spine to neutral, creating a straight line from the head to the tailbone. (purebarre.com)
No matter what position you use, hold your baby so his body is in a straight line from his head to his feet. (pregnancy-info.net)
The general rule is that your neck should be kept inline with the torso, maintaining a straight line from head to the hips. (fitnessandpower.com)