All through her late teens and early twenties – when many young women are caught up in study, careers, friends, boyfriends or girlfriends – Rebecca Saunders was considering how she might have a baby. 

At 16 years old, after being diagnosed with polycystic ovary syndrome, Rebecca was told that if she wanted to have a baby, she should do it before she was 25; one year later, doctors told her she also had endometriosis – and that this would further reduce her chances of having a child.

“It was constantly hanging over me in my teens and twenties,” says Rebecca, now 35. “I went off to university, I wanted a career, but when my friends weren’t even thinking about their fertility, it was something I had to think about all of the time.”

She believes the pressure of facing fertility issues while being single was a contributing factor to the depression she suffered with in early adulthood, because it heightened her awareness of the clock ticking down.

“I thought ‘No man is ever going to want me because I can’t have children’,” she says. “As time was going on, it was like: ‘Now I’m 19, now I’m 20, I still haven’t met anybody, I’m never going to have a baby’.”

Being diagnosed with a health condition that affects fertility or finding out you have a low ovarian reserve – which means you have a decreased number of healthy eggs – can be difficult for any woman who wants to have children. But facing a diagnosis when you’re single can raise additional challenges.

Byony Farmer, 21, from Surrey, has adenomyosis, a condition where the cells of the lining of the womb are found in the muscle wall of the womb, which is often referred to as the “sister condition” of endometriosis. It tends to get worse over time, so Bryony was told she should have children before 30.

“When I finally got diagnosed [in January 2018] I’d already had problems with my periods for about five years, so at first it was a relief, but at the same time I’ve always been very maternal, so I was also nervous as well,” she says. 

Bryony, who is currently single, explains that she faces an added issue in that she identifies as graysexual, “one step to the right of asexual,” she says. “I’m straight and I do experience attraction to guys but it’s very rare.”

[Read More: What it’s like to discover you were born without a womb]

That creates an extra pressure when you’re on a countdown to meeting someone you might want to have children with – and who you’ll need to be sure is ready to have them with you. “They would need to want kids,” Bryony says. “And I would have to say to them: ‘Look, it’s probably going to be in the next couple of years that we need to look into this.’”

It’s not usual for the threat of infertility to result in the course of a relationship speeding up. One woman who was diagnosed with PCOS in her late teens says she then rushed into marriage. “It basically led me to find someone, anyone, get married and have children all super quick. Low and behold I was divorced before 30,” she says. 

“It definitely added pressure and in hindsight I think contributed to me ending up settling with the wrong man, but I have two kids from it to be thankful for.”

Bryony has decided that if she hasn’t met the right person by the time she’s 25, in four years’ time, she will start looking into the possibility of a sperm donor. 

The latest data from the Human Fertilisation and Embryology Authority (HFEA), which regulates fertility treatment in the UK, reveals a growing number of single women are choosing to become parents alone. The number of IVF cycles completed by single women increased by 4% in 2016-2017.

Professor Geeta Nargund, medical director of Create Fertility, notes that she’s seen a “significant increase” in single women undertaking fertility tests and attending open evenings at her clinics. “Finding out that you might be facing any form of fertility issue can be difficult,” she says. “But being single does not mean that this should be any more of a worry as there are a number of steps that can be taken to both address any issues present and take preventative action.” 

One option for women wishing to preserve fertility and delay motherhood might be egg freezing, Professor Nargund adds. The treatment is expensive, costing an average of £8,000, yet it is the fastest growing fertility treatment in the UK. 

[Read More: ‘The clock is ticking’: why women freezing their eggs are still running out of time’]

Ariel Carson, 24, from Fulham, plans to freeze her eggs if she’s still single by the time she’s 29. With a family history of early menopause, doctors have warned Ariel that she’s also likely to experience this in her thirties. “I keep a credit card with at least £10,000 available to cover the costs of egg freezing and IVF,” she says.

Advances in fertility treatment mean that she no longer feels pressured to find a longterm partner. “From the time of my teens, I have had a near-constant awareness that the clock towards zero for children is always ticking,” she explains. “But I don’t feel rushed when it comes to dating and I’m not fixated on the idea of marriage. ”

If she doesn’t meet a romantic partner, Ariel says she imagines herself co-parenting “with a man who wants to be a father, not necessarily involving a sexual relationship”.

But even if you don’t want to have children, fertility problems can make dating difficult. Emma Chittenden had a hysterectomy at 36 after doctors discovered she had “a fibroid the size of a melon”, which led to premature menopause. That has hugely affected her ability to find a partner, says the 42-year-old.

“I’d been made to feel like I was damaged goods by someone I was seeing at the time and I didn’t want anyone else to make me feel like that. It completely knocked my confidence, so I stopped looking,” she says. “Rejection because you’re not someone’s type is easy enough to deal with – rejection because of something beyond your control is heartbreaking.”

Rebecca did eventually find a partner who wanted to be with her regardless of her dual PCOS and endometriosis diagnosis. Just as she was approaching the 25 “deadline” doctors had given her to have children, she met her husband, Dean. One of the first serious conversations they had was about her potential fertility issues. 

“It made me feel embarrassed and a bit sad. I didn’t feel like a proper woman, but Dean is one of life’s good guys and he said: ‘I don’t want to be with anybody else, so if we have to do it without children, that’s what we’ll do,’” Rebecca says.

Three years later, the couple were married and to their surprise, Rebecca quickly fell pregnant with their first child, Seb, who was born via a planned c-section because he was breach. With the help of fertility treatment, the couple have since had a second child, Jessica. 

“I remember them giving Seb to me after my section and I’ve never cried that way. It was just relief,” she says. “This baby that I was holding was mine, after being told for the best part of 16 years that it would never happen.”