When I had Riley we had a visiting nurse come to our home on a monthly basis that evalutated the milestones that she was or was not reaching. She was very quick to point out that even though Riley was lagging behind in some things like motor skills, she seems to be going through leaps and bounds verbally, and that what most often happens is that one day baby will "turn off" the skill that they are more ahead on and start performing the other tasks. Riley still is quite verbal for a one year old, having many words and learning to communicate very well, where she crawled late, is cruising, but has made no effort to take her first step. She does everything on the end of the time frame. If you are really concerned there is no reason that you can't have an appointment with your pediatrician (not a family doc) and discuss this or wait until the 6 month mark and do it a the well baby exam. Looking through my paperwork the nurse provided it said that babies generally don't start pushing up until at least 4 months, most by 5 months, and many not until 6 months. Hope this helps