The Prime Minister chatted to new mothers at a community centre in Branton, west of Doncaster, in an hour-long visit ahead of tonight's Question Time in York.
Exclusive: Theresa May and Jeremy Corbyn reveal their rival visions for YorkshireMs Flint's Don Valley constituency is a "seat of interest", according to Tory sources.
The Labour former Cabinet minister secured an 8,885 majority in 2015.
The Conservatives want to win over Ukip's 9,963 votes to cause a major upset.
It comes after Mrs May insisted on Thursday there were no no-go areas for her party.
"I've always believed in campaigning everywhere actually, (it's) always been one of my things," she said.
"I remember one of the first times I stood as a councillor in London and someone said: 'Oh, don't go on that estate', and I said: 'No, we campaign everywhere, we canvass everywhere.'"