Reading the gossip columns, you can only conclude that immaculate conception has become commonplace. Atomic Kitten Kerry Katona is the latest celebrity to profess to be surprised to discover that she is pregnant, in this case by her boyfriend Bryan McFadden of Westlife. So tell us, Kerry and Bryan, what did you THINK you were doing when you were making babies? Did no one ever tell you the facts of life? Did you think you could be pregnant or not pregnant merely by wishful thinking? Did the condom burst? Did Kerry forget to take her contraceptive pills?

Any explanation would be better than the feigned bafflement of parents-to-be who, if they were genuinely surprised, cannot be prepared for the tough realities of parenthood, a long, hard road filled with as much pain and sacrifice as joy. Rich young performers are exceptional in that they have the money, at least, to pay for childcare and help in the home while they continue their careers. But in doing this they are showing their young fans an unrealistic view of the implications of unplanned pregnancy.

And money doesn't protect you against self-delusion. Many of the current generation of teens and 20-somethings seem to have a mental block about conception and contraception.

When I was their age, contraception was a political act worth fighting for. It was also how you looked after yourself and ensured a stable future. You would no more have recreational sexual intercourse without using contraception (unless you wanted a baby) than you would chop your own hand off. We saw babies as a huge responsibility, so much so that premature unplanned pregnancy, in our eyes, could wreck your life. It still can. Education, careers, personal fulfilment, fun - all these have to be sacrificed when parents are too young.

And when they are not sacrificed by the parents, somebody else is paying their own price - usually the grandparents.

Over Christmas I overheard a young single father in a Dublin pub as he received a mobile phone call from his own father, who was babysitting the young single father's daughter. Grandfather, it seemed, wanted to know when father would be home, because, grandfather thought, father was spending too much time socialising and too little time with his daughter. From the ensuing pub conversation, I gathered that the young father was annoyed that his parents were complaining.

I know of youngish grandparents, grandmothers especially, who have given up on their own dreams - of returning to careers or education or fulfilling leisure time - in order to pick up the pieces of their children's unplanned pregnancies. A substantial proportion of an entire generation of grandmothers in their 40s and 50s, who reared their children full-time in the home, now find themselves caught for a second generation rearing their grandchildren full-time in their homes.

This is not a tirade against single parenthood. Single parents can be as good or bad at parenting as anybody else. If a single person is ready for the economic and emotional responsibility of parenthood and wants to have a child, that's fine by me.

What I object to is people becoming parents by mistake, when there is no excuse for such a mistake. Readily available contraception is 99 and even 100 per cent foolproof. Hormone injections, for example, can guarantee infertility for six months at a time. At least one GP I know offers depoprovera to 16-year-olds who become sexually active (along with a serious talk about sexually transmitted diseases and the need to use condoms to protect against disease in addition to hormonal contraception).

Even with contraception, there is always a small risk of pregnancy which young people must acknowledge. There is no excuse for being "surprised" at getting pregnant. Pop stars who claim to be are setting a bad example to their young fans. (I acknowledge that sometimes women claim they did not intend to become pregnant, when they were actually planning it all along, since pregnancy is now seen as a way of getting commitment from a man in advance of engagement and marriage. That's a whole other issue.)

What a great role model our children would have if a female or male pop star, rather than flaunting his or her fertility like a fashion accessory, would openly talk about enjoying sex with contraception, and about intending to plan pregnancy for the right time and relationship.

This would really be going against the grain, because stating that you intend to have sex is a greater crime than getting pregnant among the current young generation. Crisis pregnancy counsellors tell me how frustrated they become at hearing young women say that they got pregnant because "I got carried away". Apparently, to seek out contraception before having sex is the same as admitting that you are intending to have sex and enjoy it - which makes you a "bad girl". To be a "bad girl" is a greater crime, it seems, than being a "good girl" who gets carried away and ends up pregnant.

We could prevent a lot of crisis pregnancies by turning the thing round and teaching girls and young women that it is the "good" girls who plan to have sex and use contraception accordingly.

Same goes for "manly" boys who have a "right" to enjoy sex but who don't have irresponsible sex by getting girls pregnant when they don't intend to.

If we could do that, we'd go a long way to preventing crisis pregnancies, traumatic abortions and ruined lives.