Audio problem: Baby Matthew is supposed to be screaming his head off, when Prue levitated the contents of her purse to cheer him up. But she turns him to the camera and he is smiling. (00:21:40)
Visible crew/equipment: While Phoebe is telling Prue about the abandoned baby, Piper comments that the baby is like a car alarm, and as the sisters walk into the foyer the white T-mark is visible on the rug in the foyer. (00:07:20)
Continuity mistake: When Matthew starts crying and Piper freezes him, Prue puts her hands on her forehead. In the following close up, her hands are brushing her hair back, then back on her forehead in the next wide shot. (00:23:00)
Answer: That was a mistake in the series.
Also, the episode is called 'Babies First Demon' and this alone tells us that it's Wyatt's first time in the field (so to speak) and as the sisters say, they've done a good job of clearing up their own magical messes so far. Nobody really knows how advanced Wyatt's powers are, or will become. That's why the cleaners appear, to nip things in the bud. The Cleaners didn't want to chance that the sisters could clean Wyatt's magic up, just incase they couldn't. Therefore intervening themselves, just in case.