Pregnant women who smoke cigarettes nearly double their risk of losing their babies, researchers at Columbia University have learned.

The finding is the latest in a flood of bad news for women who smoke. And the news comes as health authorities are worried over a steady increase in smoking among teenage girls, while smoking among teenage boys may have dropped.

According to a series of medical reports that have piled up since 1972:

Cigarette smoking causes a 30 per cent increase in the chances of perinatal deaths - that is, deaths of a child late in the pregnancy or in the first seven days of its life. The normal perinatal death rate is about two per 100 pregnancies; the rate among smokers is about 2.6.

The babies of women who smoke weigh seven ounces less at birth, on the average, than the babies of non-smokers. Also, smokers give birth to two to three times as many babies weighing less than 5 1/2 pounds. Doctors find a high correlation between underweight babies and babies with other problems.

There is a growing toll of lung cancer among women, which apparently became a important disease in females later than in males imply because men started heavy cigarette smoking 20 years earlier. Cancer authorities expect 22,000 new cases of this disease (and 20,700 deaths) among women this year, compared with 20,000 cases (and 18,000 deaths) in 1976.

The newest report on what happens to cigarette smokers' babies comes from Drs. Jennie Kline, Zena Stein, Mervyn Susser and Dorothy Warburton of Columbia University and the Mental Retardation Unit of the New York State Psychiatric Institute. The report will be published in today's New England Journal of Medicine.

The doctors studied 574 women 18 to 40 years old who had spontaneous absortions in three Manhattan hospitals from April, 1974, to August, 1976. They also studied 320 women who delivered their babies normally.

They found that 41 per cent of the women who aborted, but only 28 per cent of those who carried their babies successfully, were cigarette smokers.

"The inference is that the risk for the smokers is nearly double," Kline said yesterday. "Women who have spontaneous absortions are 1.8 times more likely to be smokers than women who do not.

"If a woman is serious about having a pregnancy with as little risk as possible to the baby, it would be wise not to smoke."

In the past 12 years the percentage of American adults who smoke cigarettes has dropped from 42 to 34 per cent. Of men 21 and older, 39 per cent smoked in 1975, compared with 42 per cent in 1970; of women 21 and older, 29 per cent smoked in 1975, compared with 30.5 per cent earlier.

But 15.3 per cent of girls 12 to 18 were regular smokers in 1974 (the latest figure), compared with 11.9 per cent in 1970, while only 15.8 per cent of boys smoked, compared with 18.5 per cent in 1970.

"These teenage girls are now young adults, and it's in the late teens that we're seeing a good deal of childbirth today," said Preiscilia Holman of the National Clearinghouse for Smoking and Health.