Senior social worker Gillian Turner told Renfrew-shire Council's lawyer, James Wolffe QC, there was no evidence that Kimberley Hainey was not parenting Declan appropriately, but said she had "a number of concerns" about the case.
Her biggest concern, she said, was that she had never seen, and never did see, Kimberley or Declan.
And she revealed that, after drugs worker Jill Stevenson said Declan looked pale in April 2009 - the one and only time Ms Stevenson saw him - she wanted the case to be investigated further.
She told the inquiry that staff believed Hainey was depressed.
But she said that her staff and her department looked on the development positively because Hainey had reached out to her drug worker, and asked if they could see a doctor together.
She said: "There were no concerns. No one had raised concerns.
"As a mum, Miss Hainey, wanted to access services and wanted to attend with Jill Stevenson, this was a sign that she wanted to look at issues she had in her life and would be seen as engaging in social work services.
"This was an issue that she had identified with herself and Jill discovered that she wanted to assess this issue."
Miss Turner, who previously worked with North Lanarkshire Council, said that the Hainey case was "a low tariff case" and one in which there should be "minimal intervention."
She told the inquiry that no members of Hainey's family or her neighbours had ever contacted her department to say they were concerned about Declan.
Declan was found dead in his cot in March 2010 and Hainey, 39, was later jailed for neglecting and murdering him but was released last April on appeal.
The Fatal Accident Inquiry continues at Paisley Sheriff Court.