Nearly half of the nation's married women with children 1 year old or younger are in the labor force, according to Labor Department figures.

Since 1970, the rise in the percentage of mothers working or seeking work "has been phenomenal," said an article in the department's Monthly Labor Review documenting the entry of mothers into the work force in the past generation.

In March 1970, 24 percent of married women with children 1 or under were in the labor force, but in March 1984 the figure was 46.8 percent. The figures for those with older children were higher and, overall, of married women with children under 18, about three-fifths were in the labor force in 1984.

The figures clearly show, the article said, that women do not leave the labor force after having children.

"The relatively high current participation rates of married mothers, especially those with infants, attest, in part, to the turnaround in society's attitudes regarding the employment of such mothers. The rates also reflect the fact that married women often delay having children until they have established themselves in the labor force," said Howard Hayghe, a department economist who wrote the article.

"Most employed mothers -- 71 percent in March 1984 -- work fulltime (35 hours a week or more). Even when the youngest child is under 3, about 65 percent of employed mothers are full-time workers," Hayghe said.

The figures show that black married mothers are somewhat more likely to be in the labor force than white, but the reverse is true for divorced, separated or never-married women. Such black women are statistically younger and less educated and have more children than their white counterparts and therefore have more trouble finding a job. Hispanic mothers, whether married, divorced, separated or never-married have the lowest labor-force participation rates.

"Part of this difference undoubtedly lies in Hispanics' cultural heritage and part may stem from the fact that Hispanics, on the average, have completed fewer years of school than white or black," Hayghe said.