A male contraceptive pill will soon be here but do women really want it? According to a chuckling John Humphreys on Today (BBC radio 4) this morning the men of the future are going to say "don't worry dear I am on the pill" before they haul unsuspecting young maidens into bed, impregnating them and presumably disappearing into the night. Well I am sorry but I know few young women daft enough to fall for that one and frankly my concern is not so much for the men who forget to take it as for those who won't stop taking it.

While we are transfixed by the idea that men might at last be able to share the loss of libido, weight gain, and general grumpiness which so often accompany pill taking for women we are in danger of losing track of the bigger issue: control of conception. The pill gives women control of the fertility tap. She decides when to turn it off but just as important she decides (after discussion we hope) when to turn it back on.

It is easy to forget in the heat of debate that we don't just want to stop babies. We want to have them too. That wanting is not logical, it is not therefore easily planned. For me (and I suspect most women of my acquaintance) wanting a baby is about holding a warm sweet weight in your arms, about the feeling that seems to run through your bones and end up twitching the corner of your mouth into a smile. It is something akin to, but quite different from, desire. I don't pretend to know how men feel about babies (I am sure you will tell me though). My sense is that most regard pregnancy first with shock (have I really done that?) then panic (can I pay for it?) and then wonder. It is the wonder that gradually turns to love.

At the moment it is the woman who retains control over the moment at which that melting in the bones feeling is allowed to over-take the firm "no this would ruin my life" feeling in the head. Of course we all know stories of women who have put off having babies because their partner doesn't want them. (Too often they end up alone when their partner leaves and shacks up with some women who immediately gets pregnant.) But it is, I would suggest, quite rare for a woman who has a fertile partner and wants to have a baby, not to find someway of convincing him that it would be a good idea. Sometimes it is not so much convincing him as presenting him with a fait accompli - just letting nature take its course.

What will happen when it is the man who controls the tap? Of course lots of mature couples will maturely make a decision to stop taking the pill when the house has been bought and the job is secure. But what about the people who are never quite sure that the time is right? What will happen to their babies? Will the male partner feel able to risk making a 'mistake' when it is his partner who will carry the burden of the pregnancy? Will the woman feel able to persuade her partner to stop taking the Pill when she isn't really sure herself that this is what she wants? Ambivalence is normal when contemplating a decision that will truly change the rest of your life. But ambivalence can be a tricky thing when one person carries the can for the decision while the other controls it.

And on a lighter note, if a couple do decide to stop taking the pill and try for a baby will they make the sort of mistakes that women so often make? I have lost count of the number of students who get pregnant in their final year. They obviously meant to have a baby after finishing their course but they mistimed it. It was their mistake, they take the rap and somehow manage to struggle through the last part of their degree. How are they going to feel when it is their partner who mistimed it? Will they forgive him as they try to juggle finals with a baby on their laps?