When Mary LaMontagne was pregnant with her last child in 1972, the thought of returning to work part time following maternity leave didn't cross her mind. But when her supervisor suggested that they experiment with a part-time schedule, she was delighted.

Although legislation to expand part-time opportunities for federal employes was pending in Congress in 1972, the Federal Employes Part-Time Career Employment Act didn't become public law until Oct. 10, 1978.

The law defines part time as voluntary, regular employment of 16 to 32 hours, distinguishing permanent from non-career part timers. Personnel ceilings, starting in October, will be based on hours worked rather than on number of employes on the payroll. In short, one option for a manager will be the hiring of two 20-hour employes instead of one full timer. (Career part timers in federal agencies are eligible for the same fringe-benefits package as full-time career employes, with most benefits prorated).

Part-time employment is now a new work scheduling arrangement; it has been used for years by public and private employers to meet workload demands. Part-time workers, however, often have been ineligible for fringe benefits and have been denied access to professional positions.

"One of the aims of the legislation was to encourage hiring of part timers at the upper grade levels," says Linda Ittner of Rep. Patricia Schroeder's (D-Colo.) House Civil Service Subcommittee, which wrote the bill.

"Traditionally, part timers had been used, but for lower-level positions. Evidence from certain private sectors and state programs that we investigated demonstrated that part timers could be used quite effecively in professional jobs.

"Permitting use of part time enables agencies to keep experienced workers who might otherwise leave permanently for child-rearing, education or retirement, and to hire qualified persons in hard-to-fill occupations."

"Managers and employes like the program," says Ed McHugh, coordinator for the Federal Part-time Employment Program of the Office of Personnel Management (Opm). "Employes want to work part time primarily because of family responsibilities. We don't have hard facts yet, but in one small sample of supervisory attitudes we found that part timers were rated by a third of the supervisors as more productive than full timers on a per-hour basis.

"This is not to say there aren't some problems. Managers have to pay more attention to scheduling, and there are always those who feel that having part timers on their staffs in some way diminishes the stature of the office. We think these problems will go away in the future because of the upcoming change in the ceiling system and the growing recognition that part timers can be valuable additions."

About 6,000 of the 20,000 permanent part-time jobs set up in the last two years have been at the GS-5 level and above, according to McHugh, and about 1,200 at GS-11 or above.

LaMontagne, 35, Rockville, had been working full time at the National Labor Relations Board for five years when she thought she would have to leave permanently after the birth of her first child. But her part-time schedule has been so successful (she is now a GS-12) that she has continued to work a 20-hour week. In 1975 and 1979 she took maternity leave for five more months for two more children before returning to the NLRB.

She now works a 6-hour day on Tuesdays and Thursdays, and an 8-hour day on Fridays.

"The advantages of the part-time arrangement," says LaMontagne, "are especially true now since my husband is off on Fridays, and he's able to spend that time with our three daughters."

Louise Wides, 39, was hired on a part-time basis by the Federal Election Commission in 1975 as an information specialist because of her previous work with federal election campaign laws. Working three days a week, Wides has been promoted gradually and is now a GS-13 deputy assistant staff director for Information Services and chief of publications.

Wides says that the routine and pattern of the publications office is built around her Monday, Wednesday and Thursday schedule. The publication deadline, she says, acts as a "desirable constraint. If anything, it tightens up procedures for staying on schedule."

One drawback to part time, she admits, is that "It reduces time for socializing, and limits involvement in the informal networks. It may also limit the type of position one might aspire to."

Still, Wides, the mother of a 9- and a 6-year-old, feels the benefits outweigh the problems.

"I started to work part time because I didn't want to give up either of two activities I love -- being a mother and working. I knew that to have a position of sufficient remuneration and interest in the future, I'd have to keep my job skills current, but I didn't want to do it to the exclusion of caring for my children.

"In these days of high inflation, the added income of my working part time is also necessary."

Economist Betty Barker, 37, works part time as a GS-15 division chief of the Bureau of Economic Analysis, U.S. Department of Commerce, where she supervises 50 employes. She had been working full time for the agency for 2 1/2 years when she requested a part-time schedule following the birth of her first child.

Barker and full-time division chief George Kruer have divided responsibilities. His administration and production, and hers, research and analysis.

Barker (who now works a 32-hour, 4-day week) doesn't think she'll return to a full-time schedule for some time. She concedes, however, that "this may inhibit my chances to move up to a division chief's position."

Barker's husband, a self-employed criminal lawyer, sometimes takes Friday afternoons off to spend with his wife and their 5- and 2 1/2-year-old sons. "We waited eight years before deciding to have children," says Betty Barker, "but once we decided, we wanted to spend time with them."

Spending more time with his family was a positive part of Peter Theil's recent two-year experience as a part-time federal employe. "My older daughter was in pre-school mornings. On a nice day, I'd bicycle over, pick her up, and we'd go for an ice cream cone and do errands together. It was very special." He also used the extra time to restore his Capitol Hill townhouse and to take music lessons.

"I'd like to work part time again in the future," says Theil, 35, "but I returned to a full-time schedule (in the legislative office of AID) largely because of monetary reasons."

Although two men in his office asked him how he got a part-time job and one, an economist, now works a reduced schedule, Theil says, "I felt many pressures form co-workers who said part time wasn't good for my career."

Theil believes this social pressure against men "is enhanced by the language of the part-time legislation which singles out women, handicapped and students."

John Yasnowsky, a GS-15 associate administrator for the Office of Plans and Programs at the National Highway Safety Administration, had been on a three-day work schedule for the past three years.

"My main reason for reducing my schedule was to purchase and operate a sheep farm," says Yasnowsky, 43, Culpeper, Va. "A real bonus has been that I have more time to spend with my sons (11 and 14).

"I was born and raised on a sheep farm, and I always wanted to own one. But I didn't want to wait until retirement because of the hard physical work involved.

"We've had to adjust our life style a little bit, but we've found we can get by on considerably less. (As a start, they tore up their credit cards.) We expect the farm to be a profitable enterprise in the future.

"I feel I've gained a lot, and enjoy both endeavors a little more by sharing the time."

For Jan Scruggs, a GS-11 Equal Opportunity specialist for the Department of Labor, a part-time schedule means that he can devote time to the Vietnam Veterans Memorial Fund he founded last April. Scruggs, 29, Columbia, Md., was decorated for valor and seriously wounded in Vietnam.

He has reduced his work week (and salary) by half -- "I manage," he says -- working Tuesdays, Wednesdays and a half day on Fridays.

Scruggs had no problem getting the reduced schedule and credits his boss as being a "very understanding person who knows how important this project is to me."

Though the scheduling preferences of these part-time workers vary (some prefer, for example, three consecutive full days, others a split work week) there are common threads. Essential to a successful part-time experience are supportive bosses, staff and families.

As Louise Wides says, "The part-time arrangement works for my office because I pay special attention to delegating authority and I have a very capable staff."

For those who supervise or work with high-level part timers, the formula for success includes the seriousness of the employe, good planning and willingness to be available during critical situations. ("All of the employes interviewed stress that they periodically come into the office on non-scheduled days to handle emergencies or to attend special meetings.)

"The workplace must become more flexible and responsive to the needs of employes," says Rep. Schroeder. "There has been considerable demand for part-time jobs from people with family responsibilities, older workers wishing to phase into retirement or return after retirement and persons continuing their education.

"The hard job ahead is implementation, which involves making managers better aware of the efficiency of part-time workers and the contributions they make to their organization. A speedy check on implementation will be to see how many qualified full-time federal employes are permitted to convert to part time when they request it.

"We made changes in the federal sector which we hope will serve as a model for employment policies in the private sector and in state and local government."