I married my girlfriend of ten years three years ago and we divorced two years ago. I never wanted children and, although she did, we agreed not to have any. Since our divorce I have met someone else and we are expecting our first child. My former wife hasn’t met anyone else and, at 39, her chances for children are running out. I feel racked by guilt and it is affecting my present relationship.

There is, I’m afraid, no getting away from the fact that if you were really that committed to remaining childless you would have had a vasectomy. And from your ex-wife’s perspective your decision to start a family with someone else simply confirms her fears that it wasn’t that you didn’t want to have children, it’s that you didn’t want to have children with her. It’s a bitter pill, but not uncommon.

In 2005, two weeks before her 44th birthday, the singer Sheryl Crow and cyclist Lance Armstrong got engaged after a two-year relationship. Five months later they called the wedding off. In a hugely misguided moment of truth Armstrong, a father of three, publicly blamed the ticking of Crow’s biological clock and claimed that he just wasn’t ready to be a daddy again. However, next month, Armstrong and his new girlfriend, Anna Hansen, are expecting a baby.

Crow, and your ex, are classic examples of “involuntary childlessness”, a term that encompasses the way in which a range of issues from careers to relationships and, eventually, biology can conspire to prevent a fertile woman from reproducing. Aptly described as a kind of “creeping non-choice” in the book Beyond Childlessness (Rachel Black and Louise Scull, £12.99, Rodale), it is a growing problem. Projections suggest that one in four women born in 1973 will be childless by the age of 45. Rachel Ormwood (formerly Black), who co-wrote the book, was married for 20 years to a man who refused to have children. She says that she made “the ultimate sacrifice” for the man she loved, yet when her husband turned 50 they divorced.

Ormwood’s advice is that “trying to help your ex will only make it harder because witnessing you becoming a father must be excruciatingly painful”. It is sad for your ex and uncomfortable for you, but it is nobody’s fault. Right now your ex needs to, as Ormwood says, “make her own journey, have counselling and allow herself to grieve for the children she never had”. She may also need to take some responsibility for the situation that she finds herself in. After five, seven, ten years with a man who continually refused to compromise on an issue as significant as children, your ex should have spotted the enormous black cloud hanging over the relationship.

Self-esteem is always the first casualty of a bad relationship and your partner clearly did not have the confidence to challenge your demand that she choose between having you and having children. Had she been more assertive about her own desire for children she would have tried to change your mind, dragged you to counselling or given you an ultimatum. Failing that, she could have left and found a partner who did want to have children. Or she might have done what millions of women in her situation have done and “accidentally” fallen pregnant in the hope that you would come round to the idea eventually. Tricking a partner into having a baby is a terrible deceit, but, frankly, if women didn’t do it the human race would have died out ages ago because so few men wake up on any given morning thinking: “Aha, I’m ready to have kids now.”

I suspect that a large part of your guilt relates to the fact that your ex is still single. When you split she was 37 and presumably you hoped that she would meet someone relatively quickly and fulfil her desire to become a mother. However, the older a woman gets, the harder it is for her to find a partner. Having said that, your ex still has her whole life to find the right man and, if she is fit and healthy, at 39 it is not too late for her to have her own child. And being single no longer prohibits women from using fertility clinics or adopting either. In May 2007 Crow adopted a two-week-old boy. And judging by the photos he makes her far, far happier than Armstrong ever did.

Explore Women

• Fashion

• Beauty

• Diet & Fitness

• Relationships

• Families

• Celebrity

• The Way We Live

• Horoscopes

Times recommends

• 12 party beauty tips
• Nutrition: is being big a genetic destiny?
• What it feels like: to pry into other people's lives