sink in – to penetrate the mind [dict]

This is an entertaining news from BBC. A woman didn’t feel well, but she went to see a doctor and was told she had been 20 weeks pregrant. Thirteen days later, she gave birth to twins. Of course, this is all good news (though surprising) to the family. “It took a while to sink in that I was pregnant in the first place”, she said during an interview, “and took a bit longer to sink in there was (were) two of them.”