If your baby has no other associated problems, feeding well and gaining weight then probably this is normal. If your baby is a female then UTI can be a possibility, but some other symptoms are likely to be there along with frequency of urination. Does your child has any preexisting kidney disease? If no then nothing to worry about. Is there winter or rainy season where you live? Urination will be more in these days. Considering all these issues you have to judge this situation. Moreover if you have any confusion or suspicion i suggest you to consult a Paediatric Nephrologist for specialized opinion.