IT HAS happened again. Yet another police officer has found that she cannot get child care because of the unpredictable hours and rotating shifts of police work. Once again, the woman officer involved can't depend on her husban ot help because he, too, is a police officer and he, took has to work shifts.

The latest incident involves Arlington Officers Charles and Marcia Gavin, veteran officers who met on the force and who had a baby 15 months ago. Marcia Gavin returned to work when the baby was 6 months old and was assigned to the tactical squad. "They allowed me to set up a schedule of working three days and two nights a week. When I worked days, my husban kept him." He worked rotating shifts, but she was allowed to switch her schedule, depending on when her husband was working.

Then, Gavin and two other women officers were suspended because they refused an assignment they deemed was poorly organized and dangerous, and when Gavin returned after her reinstatement she found herself in the patrol division. It was the only opening, says police spokesman Tom Bell.

Patrol duty involves rotating shifts. A person works four straight days of day work, then gets three days off, then works four days of the midnight shift, then has three days off, and then works four days of the evening shift. The days off change every three weeks. Nay mother who has tried to arrange child care for a regular, stable work week can tell you that it would be impossible to find child care for that kind of shift work. That's what Marcia Gavin discovered and she resigned from the department.

"Everybody's got personal problems [with the shifts]" says Bell, "but when you accept the job you're told the hours and the assumption is if you can't accept the hours then you can't accept the work."

That kind of thinking made sense up to a point, and we passed that point somewhere between the old days of the sixties and the double-digit inflation days of the seventies. The police officer who used to be able to work crazy hours because the little woman was home taking care of the kids now has to get himself home to help care for the kids because his wife is working. Bell says the majority of Arlington's policemen have working wives. "It's tough on our salaries, especially if you have children, to make ends meet. It's almost a requirement that a wife work."

Bell says most of the county's 26 policewomen are in their twenties. Although only two are mothers now, it would seem safe to assume that more and more of them will marry and become mothers and that some of them will marry other policemen they meet on the job, and that the problem confronting Charles and Marcia Gavin will become more commonplace.

It came up before in a situation involving a Virginia state trooper who was fired last December because she refused to report for two weeks of partrol duty in the coal fields of southwest Virginia. She said she was not given enough notice to arrange for child care, and her husban, an undercover state trooper, was unavailable to help out.

At the time, I wrote a column saying her problem stemmed from bad management of personnel by the state police. Okay, people said, but what happens to mothers who are police officers and who are called to duty in emergencies? What happens when you have a flood or a riot and you need all public safety personnel and the women on the police forces say sorry, I can't come to work because I can't find a sitter?

Public safety personnel are expected to respond quickly to emergencies. Police and firemen also are expected to work at odd and demanding hours. There are, in other words, extraordinary demands placed on the time and lives of police officers and others involved in protecting the public. But the news stories are telling us that the police departments have not yet begun to look at these demands in light of the new realities of the lives of people working in the departments.

Marcia Gavin complained that the Arlington department doesn't know how to deal with the problems of women officers. It is clear too, that the department has not yet decided to address the fact that the majority of its officers have working wives.

There are solutions to some of the problems police officers now face, be they men or women. Officers have to be able to work 24 hours a day, seven days a week, often when no child care is available. Police departments ought to get together with unions representing police officers and figure out how to set up 24-hour child care facilities that meet the needs of parents who are police officers.

There is no reason why all three jurisdictions in Northern Virginia can't work jointly on this problem and share in the solution. They all share the problem. There are businesses in the area whose employes have shift work and who might want to share in using the facilities. I'm not suggesting subsidized child care. I am suggesting that police departments and county governments help set up unusual child care that meets the unusual meeds of public safety personnel.

The point here is that police departments need to recognize that fundamental changes are occurring in the lives of police officers. Many of them now have to deal with the stresses of being working parents, and, therefore, the problems of child care. But police officers have a much rougher time of it than most of us: they have to cope with crazy schedules, weekend and night work, emergencies and constant changes in shifts that make it almost impossible for them to set up reliable child care.

Marcia Gavin says this is not a women's issue, that it's a family issue, and she is right. But it's also a personnel problem that police departments ought to confront creatively. Arlington's solution has caused it to lose Marcia Gavin, a seven-year veteran with a master's degree in investigation, an officer who until recently, had an exemplary record.

The department made an investment in Marcia Gavin when it hired and trained her and that investment is now lts. The department will be hiring other women and they will have children and they will have child care problems. For police departments to help their personnel set up 24-hour child care facilities that can help their employes simplify their lives is not merely an altruistic notion.It's a low-cost way for departments to help their personnel and to protect the investment they have made in the officers they have hired. That's not altruism. That's good business.