Pivoting is just what it sounds like – turning the body with the tummy on the ground. When pivoting, a baby will have her head up and her legs stretched out and she’ll use her arms and legs to pivot while curling her body. Some babies begin pivoting around 4 months of age and 50% and 90% master this ability by 6 and 8 months, respectively.
Four-Point Kneeling is when a baby is able to support her weight on her hands and knees. While this is more of a stationary ability that needs to be mastered before learning to crawl on the hands and knees, babies in this position may rock back and forth and even fall forward if they rock with enough momentum. Fifty percent of babies can hold themselves up in this position by 7 months and 90% by 9 months. Although they may be unsteady at first, within about a month they become much more stable.
In our house we call it the army crawl, moving forward by putting weight on one arm and the opposite leg and then switching to the other arm and leg, but not lifting the entire body up off the floor. Fifty percent are able to crawl this way at 7.5 months and 90% are able to by about 9 months.
Reciprocal creeping is what most people consider crawling; the baby’s weight will be on hand and opposite knee and she’ll move by shifting weight from one hand and leg to the others. Fifty and 90% are able to crawl this way by 8.5 and 11 months, respectively.
Reference: Piper M, Darrah J. Motor Assessment of the Developing Infant. Philadelphia PA:W.B. Saunders Company 1994.