Cohabitation produces two groups of losers among women and children. Most women want to have children - Gillard is an exception - and some miss out after wasting their primary reproductive years in a succession of live-in relationships that look hopeful but go nowhere, leaving them childless and partnerless as they hit 40. People often drift into living together - someone's lease runs out or they get sick of running home for fresh shirts and underwear. They slide rather than decide, and frequently fail to discuss their mutual expectations for the relationship. It's the women who end up stranded when they spend years in a succession of de facto relationships waiting for Mr Not Ready or Mr Maybe to make up his mind. Women's tiny reproductive window means they pay a high price for wasting precious breeding time in such uncertain relationships. While the de facto lifestyle leads some women to miss out on having children, others are taking the risk of becoming parents despite these unstable relationships. A growing proportion of children is now born to de facto couples - up from less than 3 per cent in 1975 to 12 per cent in 2000, according to data from the Household Income and Labour Dynamics Survey.

It is often assumed these children will provide the glue to keep de facto relationships together, but sadly this is not so. David de Vaus, a sociology professor from La Trobe University, found cohabiting couples who have children are more like to break up than married parents, increasing their risk of the negative impacts of family breakdown. If Gillard chooses to play house with Tim Mathieson in the Lodge, this choice sends a strong message to the huge numbers of women who rightly admire her and seek to follow her example. A lifestyle suited to her particular needs may be riskier for many women and their children. As a Labor politician, Gillard is hardly likely to spell this out. Her brand of politician is too nervous of offending natural constituents to express concern about lifestyle choices. But it wasn't always like that. In 1972, an intriguing discussion between Germaine Greer and Margaret Whitlam was published in The National Times. Whitlam, whose husband had just become prime minister, was outspoken in her criticism of ex-nuptial births, declaring it was irresponsible to produce children outside wedlock. When Greer confessed she was considering having a child on her own, Whitlam was forthright: ''Well, I think that's just a selfish thought.'' Later in the interview, she relented a little. ''It may be all right for people who are well known and who have position and who can organise themselves . . . but it's not OK for everybody,'' she said, questioning the impact of Greer's decision on her many fans.

At the heart of this conversation was role models. People in the public eye, our influential leaders, need to think through whether others who don't share their circumstances will follow their example and get into trouble. Every day we see well-known Australians making dubious lifestyle decisions being lauded in the media - celebrities choosing to become single mothers, unwed fathers, parents dragging children through a succession of chaotic ''blended'' families. Pat Rafter was made Australian of the Year just as he was about to become an unmarried father. What did that say to his many male fans about the importance of committed fathering? Loading Politicians today rarely question social trends, even when all the evidence is they are having negative social consequences. John Howard was the rare exception, when he went into bat for a child's rights to a father in the debate over single mothers and IVF. But the actions of our role models speak louder than any words. The well-heeled tennis hero cheerfully embracing unmarried paternity, the feminist toying with sole parenthood, the prime minister living with her boyfriend - why wouldn't their many fans not seek to walk in their shoes?

Bettina Arndt is the author of The Sex Diaries. bettina@bettinaarndt.com.au