Two years down the line, Jones has now become a mother - and says this has given her a new awareness of what mum-of-one Gemma Foster went through.
"Being a wife and a mother made me realise the gravitas of that unit falling apart, because I'd go home at night and I'd have a baby to put to bed," she says.
"So I think it definitely made me realise when two people get together and have a child out of love and then they split... what it is to parent a child and be in each other's lives when you are damaged and hurt without damaging and hurting a child."
Jones brought her son to set - he doesn't appear in the show, but "looked much better than I did" on camera, she jokes. She's now looking forward to some down time with him.
"The work/life balance for anyone is hard, so I try to keep work separate," she explains.
"I feel very, very grateful because I did a lot of work and now I'm taking a lot of time off. So I'm there until Christmas now, just down the play park in my Converse."
The second series of the BBC One drama takes up the action as Gemma's estranged husband Simon (Bertie Carvel) and his new family return to the fictional town of Parminster, where she lives and works.
They are dealing with the bitter repercussions of divorce - with their son, Tom, caught in the middle.
Jones admits it can be "uncomfortable" viewing at times but says the show has a "weird, sexy edge to it".
"We all know what it feels like to be in a room with an ex-partner," she goes on.
"Everybody has had a relationship, everyone has had exes, everybody has been in difficult circumstances. I'm sure myself and Bertie have had those thoughts and feelings; otherwise we wouldn't be able to draw on them.
"But at the same time, with the style of writing and the style of the programme, you're able to go further.
"It has a fantastical edge as well as being deep-rooted in naturalism. It also has an exaggerated way of showing how far you could go if you really wanted to."
Carvel, who played Miss Trunchbull in West End musical Matilda, says he found Mike Bartlett's writing "exciting" and that the Doctor Foster plot was a "real page-turner".
"He gives us incredibly three-dimensional characters", says the actor, adding that it was "really fun" to play a character who makes the audience change their opinion about him as the drama progresses.
"Often you find yourself looking at something from a really different point of view," he says. "That's what's exciting about this series as a whole."
Jones says the original plan was to give Gemma a new look. After conducting a screen test, though, it was agreed that it just didn't work.
"She's moved on, but actually she's comfortable with her bob and her work and she's put up her walls," says the former Coronation Street actress.
"It was the right decision to move her on but leave her embalmed in a way.
"And what I got, as well as being exciting and dark and sexy and thrilling and all those things, I looked at them both and thought, 'You're both really hurt' and I hadn't seen that before."
Bartlett - the man behind award-winning play King Charles III, recently filmed by the BBC - says he originally intended Doctor Foster to have a single series.
"But when we were shooting it, I started to realise there could more - there could be another story or a further story to tell," he explains.
The first series' final scene saw Gemma and her son together, seeing her former husband with his pregnant new partner.
"It looks like a happy ending, but there are lots of threads untied", Bartlett goes on.
"There's more to tell, so when we had the opportunity, I thought we should."
Doctor Foster returns to BBC One next month.
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A lot has changed for Suranne Jones since we last saw her in Bafta-winning TV series Doctor Foster, in which she plays a GP who suspects her husband is cheating on her.