My child is twelve months going on thirteen, but cannot walk. However, he started mimicking sounds as early as 8 months and can now speak fairly understandable words. Could there be problems with his ability to walk?
From what I've read and from personal experience, I would say that you have nothing to worry about just because your son cannot walk at 13 months.
According to these websites, it's normal for babies to start walking any time between 9 and 18 months:
My son started taking a few steps in his 13th month but wasn't walking confidently, particularly outside, until 14 to 15 months but he happened to still be ahead of most babies of similar age that we know. It depends who you have around you - probably in another group of friends he could have seemed behind.
One of my son's little friends wasn't walking until nearly 2 years old but as soon as she started she could walk very well within the space of a week whereas my son did it much more gradually. Another of his friends only started walking at 16 months and by 2 years was running and climbing all over the place.
At this age I would be looking more for progress towards walking. Is he pulling up to standing using furniture? Can he walk a bit with help - starting with two hands and then just one? He may start to stand for short periods without holding anything. If you are concerned that he's not doing any of these things or making progress then it might be a good idea to mention to your doctor but even then I probably wouldn't worry too much for another month or two.
This is one of those things where it seems very important while you're waiting for it to happen but once your child is walking, no-one else will even know or care when he first started. Nor does it seem that it affects how the child develops in the future. Even a few months later a 'late' walker can be doing just as much or more than an early walker. Children develop at their own pace. Starting to walk depends on a lot of factors, from physical strength to mental development, the child's personal interests and temperament:
My daughter didn't start crawling until her 1st birthday. She was walking when she was 18 months, and now at 2 she runs and climbs all over. She was also an early imitator/talker and says sentences now. I think she didn't crawl until she was 1 because she was an only child and we gave her anything. She needed motivation to make the effort.
Of my three children, each started walking at a different age. The youngest did not walk on his own until nearly 14 months -- he was very cautious about his balance, and apparently did not want to risk falling over. The middle one started walking around 12 months, and the oldest was walking at 13 months.
Children meet developmental milestones at different times: children may be walking by 12 months, but not all will be. Some children walk as late as 15 or 16 months. (Ref. Denver II Developmental Milestones chart -- look towards the bottom for gross motor skills, which include walking.)
If he has not met other age-appropriate milestones (crawling, sitting without support, standing, "cruising"), take your son to a pediatrician and be specific about why you are worried. A doctor has more information and expertise, and can take additional factors into account.
From my experience children are usually either "walkers" or "talkers". The ones that walk early have lower language skills and vice versa. There are also ones more in the middle of the spectrum, but they mostly seem to lean one way.
My daughter showed no interest in walking or even crawling or getting up on hands and knees until about 14 months. At that point she suddenly decided it was important and started crawling, and then walking within a few weeks.
Don't worry about it. Focus on language if that's what interests them right now. Eventually, they will decide that movement is important and will work on it. There's no cause for worry at this point.