Google have less url´s in the index

Hello, I am seeing some weeks ago to now that in the Google Sitemaps, Google are taking less url to the URL index in Web pages. I have more URL that I have sent, but they are taking less :( This is a problem?

The sitemap is merely a suggestion of urls. It does not guarantee that any will be indexed at all. It is entirely up to google what they want to include in their index.