They are putting off having children because they prefer to focus on their careers, have more money and enjoy spending more time with their friends and partners.
But many said they longed to start a family but either hadn't met Mr Right or were with a partner who didn't want kids – a situation described by the magazine as 'emotional infertility'.
The poll of 3,000 women aged 28 to 45 is revealed in Red magazine's 2012 Modern Motherhood Report.
The magazine's health director, Brigid Moss, said: "Women simply aren't meeting the man with whom they'd like to have children at the time when they're most fertile. Or they're not in a secure financial situation.
"Some women have what we've dubbed 'emotional infertility', that is, they want children but haven't met a partner who wants children yet.
"For those women, not having a partner has made a huge difference to how they planned their life to be.
"We all know someone with emotional infertility. A doctor can't help.
"But a significant minority of women – one in five – have considered having a baby alone. If they go ahead, it's proof that having a baby is more important to them than being in a relationship."
One in 10 women who took part in the survey had IVF and on average they paid just over £7,200 for treatment.
"It's become more acceptable to talk about medical infertility with your friends and family, so women can now be more open about that," said Moss.
"But it's very hard to confess that you're desperate for a baby, but haven't met anyone."
One woman, called Nicola, who took part in the survey said she decided to find a sperm donor after her 40th birthday.
She used a website which specially matches women with donors, and became pregnant a few months later.
• Red's survey was carried out for the Red Modern Motherhood Report, which appears in the October issue.