Back in the '70s -- that decade that saw the massive influx of women into the work force -- the professional survival ethic for women was to emphasize that they could do everything a man could do -- if need be, better. The higher a woman got in a corporation, the less female company she found; she emphasized sameness with her peers, not differences.

She wore the pin-striped suit, carried the attache case, and if she did the one thing a man couldn't do -- namely, have a baby -- she acted like nothing really different was going on. She worked until the first contraction. She took as little maternity leave as she could -- no debenture offers were going to get halted on superwoman's account -- and returned from childbirth without skipping a beat. Motherhood was not going to interfere with her career.

Ignoring the fact that women also became mothers was not, however, a particularly realistic approach to handling the often competing demands of work and family life.

One of the healthiest trends going on in the mid-1980s is a recognition that there are, indeed, biological differences between men and women that generally lead to differing roles in child rearing and different patterns of work life. Part of what has made this acknowledgement possible is the fact that women have reached a critical mass in the work place.

They make up nearly half the entire work force and half of the professional work force. Half the mothers with children under 3 are working, as are more than 60 percent of mothers with children ages 3 to 5. Their sheer numbers make them a critical factor in the well-being of the economy and in the smooth functioning of many individual companies. There's company in numbers and there are enough working mothers in the professions that they and their male colleagues (who have working wives) are more frequently willing to assert their parental obligations and to insist that companies accommodate these considerations.

Thus, there is more pressure in both public and private sector labor contracts to establish maternity leave, paternity leave, leave for adoptive parents and use of personal sick leave to care for dependents who are ill.

Hearings were recently held by the House subcommittees that oversee the federal government to examine its parental and medical leave policies. A staff report by the Civil Service subcommittee revealed that the government has no uniform policies in these matters and that they are often set on an office-by-office basis. The report found that few agencies provide leave to adoptive parents, and maternity leave is treated as a form of sick leave. Women can take a maximum of six weeks' leave before birth and six to eight weeks' leave after birth to recover, but they have to use accumulated sick and vacation leave to do so.

A representative from Southern New England Telephone told a subsequent hearing on parental and disability leave in the private sector that her company instituted the benefits so that mothers could return to work when they were able to "and the company retains a valuable asset."

That is perhaps the most important talking point for the numerous approaches that have been developed to help parents mediate conflicts between child rearing and work. Employers who have an extensive female middle- management cadre in place have years of training invested in people who know the corporation, how it works, what its goals and ethics are. These women, by virtue of what they have had to overcome to succeed, may be among the best and brightest of the company managers -- and these are the very people most likely to balk at policies that create conflicts between family and work.

In a work life that ranges from about 22 years of age to 65 years, the number of months and years that will be heavily affected by childbearing responsibilities are relatively small. Not a great many women, for example, can afford to take an entire year off to be home with newborns -- but if they take two or three years off to have babies out of a period of 43 years in the work force, that should not come as an economic tidal wave for most employers.

Chalk it up to conditioning or biological destiny, it doesn't much matter: Working mothers are wrapped up in their children's care in ways most fathers are not, particularly when the children are small. Increasingly, they are willing to acknowledge these differences and to imprint a new ethic on the work place that views recognition of workers' family responsibilities as the mark of a good employer. Companies that don't are going to lose the best and the brightest to those that do.