Gosh, thats nothing to worry about at all. When my DD was that age, we were really worried and counting words up until just before her 2nd birthday.She'd had a few persistent middle ear infections. She is now 3.5 and talks a lot better than others in her age group.

My DS is 19.5 months and he says dada, mama, Bree (sister) nana, woof woof, ah (as in ta - please and thankyou) og (dog), up. So that's only 8 words. I think he's just like his sister and his expressive language is just going to develop gradually. Receptive language is the super important issue at this age. As long as he understands everything you tell him/ask him, all is good.