It has been quite a year for Ayòbámi Adébáyò. She is in London for International Women’s Day, as she was last year, when it was announced that her first novel had been longlisted for the Baileys prize. Stay With Me went on to make the shortlist and is now up for the Wellcome prize, the winner of which will be announced later this month. The novel was glowingly reviewed, not least by the New York Times’s high priestess Michiko Kakutani (“stunning”, “powerfully magnetic and heartbreaking”); Sarah Jessica Parker chose it for the American Library’s book club; and the author, who has just turned 30, has been interviewed in both the Paris Review and Vogue. When we meet, she has come from the BBC, where she had been discussing the #MeToo movement in Nigeria. “It’s complex and very different across regions, across class, maybe even across religions,” Adébáyò says, describing what it means to be a young woman in her home country. “I think there is a dissonance between how much is expected of you as a young person, whether you are a man or a woman: you are supposed to go to university, you get a master’s degree, maybe two, particularly if you come from the middle class.

“And somehow, when it gets to a certain point, there’s a separation in how far you can go because a woman is to subsume all of her ambition to – some would say – the ultimate goal of marriage. To be fair, men are also pressured into getting married. But I don’t think men are expected to make the sacrifices that are routinely expected of a woman.”

The deaths of two of her close friends in their teens from SCD was the tragic inspiration for the novel

The intense pressure on women to become wives and mothers is at the heart of Stay With Me, in which the story of a marriage unravelling is set against the turbulent backdrop of Nigeria in the 1980s and 90s. Told in turn from the perspectives of wife and husband, Yejide and Akin, the novel shows what happens when romantic love comes up against social expectations, as Yejide’s failure to conceive becomes a family matter in a culture where a second wife is seen as the obvious solution. Folk tales, gossip at the hair salon Yejide owns, mother-in-law Moomi’s bossy superstitions and bulletins of military takeovers – Stay With Me captures a country and a couple in conflict, pulled between tradition and modernity.

One scene, which would be comic were it not so grotesque, records poor Yejide’s pilgrimage to the Mountain of Jaw-Dropping Miracles, culminating in her breastfeeding a goat. When she finally has a baby, Yejide discovers that she has passed on sickle cell disease.

Infertility and the loss of children might seem audaciously challenging subjects for a first novel, let alone one by a writer then in their 20s, but they are issues which Adébáyò has been thinking about for some time. She was at university when she discovered that she was among Nigeria’s one in four healthy people who are carriers of the sickle cell gene, making it the country most affected by the disease in the world. The depiction of the devastating impact of SCD on families earned the novel its place on the Wellcome list, a prize for fiction or non-fiction that engages with medicine or illness.

“I was thinking of dating someone ...” she says with a big, ready laugh when I ask her about why she decided to take the test then. “It makes for awkward conversations. But it’s better to know as early as possible. Because if you become emotionally involved with somebody it’s more difficult to say to yourself: ‘I’m going to walk away from this because I don’t want to make a decision that could have an impact on somebody who’s not here.’ ”

My uncles would discuss politics and we would just tell them ‘don’t say that outside’. Because people did disappear

It’s possible, she continues, “that you could have a child that wouldn’t have the disease. But it’s also possible that you have a baby who does. And it’s also possible that you have five children and they all have the disease. It’s a complicated thing on the level of personal ethics.” Of all those she knows who live with the illness, Adébáyò told BBC Radio 4’s Woman’s Hour last year, “every single one of them said to me they wish their parents never married”.

The deaths of two of her close friends in their teens, and the effect on their families, were the tragic inspiration for the novel. Each crisis is harrowing. “I just couldn’t stop thinking about what it meant for the mother,” she says, recalling how she would still bump into the mother of one friend occasionally. “Not just to experience that kind of loss, but to somehow get up the next day.”

And so the central character of Yejide – a beguiling combination of vulnerability and strength – “just came to me”. The idea started as a short story, which she “sat on for a couple of years, maybe longer”, but there “was just something very vivid about the character that I had to pay attention to”.

Like Chimamanda Ngozi Adichie’s Orange prize-winning epic Half of a Yellow Sun, set during the Biafran war, Stay With Me records a period of modern Nigerian history, beginning with the 1985 military coup, a few years before the author was born. Why did she choose to return to the political landscape of her parents and grandparents?

Women waiting to register to vote in Kano, 2015. Photograph: Goran Tomasevic/Reuters

“I was very young when the 1993 elections were annulled,” she says. “All I remember about it was that I didn’t have to go to school and I was very excited about that. I did remember my parents were sorely disappointed ... The level of frustration that many people felt, the disillusionment of thinking that any moment now we were going to go back to democracy and having that hope dashed and postponed and then eventually dashed totally. I think it had quite an impact on us as children.”

Drawing on “the atmosphere of fear” that hung over her childhood, she made the Lagos and Ilesa of the novel unsettling cities of armed robbers, power cuts and protests. “Sometimes I would be at my grandfather’s place and my uncles would discuss politics downstairs and we would just tell them ‘don’t say that outside’. Because there were people who did disappear, that sort of thing started to happen.”

By the time it was the 80s polygamy was still possible. But I don’t think it was as fashionable as it was before.

One concrete legacy of this period can be seen in the architecture: her grandfather’s house, she explains, has no fence. “You can see everything, it’s really open, you walk in. Then, by the time you get to the 80s, fences start going up and up, most places have stayed that way.”

Cultural evolutions are slower and less visible – such as attitudes towards polygamy: “By the time it was the 80s it was still possible,” Adébáyò says. “But I don’t think it was as fashionable as it was before.” One grandfather had several wives, the other just one.

The family lived in the city of Ile-Ife, 200km from Lagos, where her mother, a doctor, also taught medicine at Obafemi Awolowo University. Growing up with one sister, who was five years younger – “by Nigerian standards I was an only child for quite a while” – she has never worried about being lonely. Her sister is still her first reader: “She’s very honest!”

Even in a household where reading was “almost a competitive sport” (TV didn’t start until after 4pm), Adébáyò had the obsessive edge: “My mother used to laugh that if they asked me to clean up my room I would spend so much time reading every tiny bit of paper, a receipt or whatever, instead of throwing it in the trash.” She recalls taking The Go-Between from her parents’ library when she was about nine: “I was just heartbroken. It was one of the first books that … oh my God, this can do this to people …”

When she was 14 she wrote a short story which ended with someone “going up in flames”. Her mother asked a colleague in her office to type it up. “She was very upset – how can this terrible thing happen? And then my mother also read it and came into my room and asked: ‘Have you had a happy childhood?’ I remember thinking ‘Yeah’ … But a lot of ideas I had when I was 14 or 15 were scary.” Writing, she concedes, is maybe “a safe place to sort of explore the scariest things”.

She studied literature at Obafemi Awolowo – Wole Soyinka was a professor there from 1976 to 1999 –going on to do an MA, with plans to become a teacher. During her final year she landed a place on a new creative writing workshop set up by Adichie, just after Half of a Yellow Sun was published. It meant going back and forth to Lagos, about three hours’ drive away. “That was when I realised that I would rather fail my exams than not take advantage of this opportunity. It was absolutely worth it.”

She has been lucky in her teachers. In 2014 she began the MA in creative writing at the University of East Anglia in Norwich (“I grew up in a university town, so it felt almost like home,” but a bit less sunny), coinciding with Margaret Atwood’s tenure as visiting Unesco professor. Her year at UEA was the first time that she didn’t feel writing “was stealing time from something else that I had been paid to do”.

Stay With Me took five years to finish, in between working crazy hours at a bank in Lagos. At the end, she was satisfied. “I felt like I would look at it in 10 years and think this is the best I could have done at that time.” The response has been “quite overwhelming”, especially in Nigeria, where, she says, people have really “taken such an ownership of the story”.

And the dreaded second novel? “There will be Nigerians ...” is all she will say.

After all the heartbreak, it’s not giving too much away to say that Stay With Me ends optimistically – or at least with the possibility of redemption.

But one thing she really wants the reader to take from the novel is how Yejide, at first “terrified about being alone in the world, makes the journey to where she’s comfortable with relying on herself. She’s always been a strong character, but by the end of the book she comes to own that strength unapologetically”

• Stay With Me is published by Canongate. To order a copy for £6.99 (RRP £8.99) go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99.