In the Soviet Union, there are more than twice as many abortions each year as live births: in France, the number is about equal for both; in England, despite very liberal laws, there are about six times as many full-term births as abortions each year.

But in seven other countries surveyed by Washington Post correspondents - Brazil, Italy, Japan, Portugal, Spain, Sweden and Yugoslavia - there is a general consistency: Despite religious, ethnic and cultural differences, they average from 1 1/2 to 3 live births for every abortion.

Clearly, there are differences. In Catholic Italy, Portugal Ireland and Spain, where abortions are illegal, accurate figures are hard to come by. in equally Catholic Brazil, where the two grounds for legal abortion are to save the woman's life or to terminate a pregnancy caused by rape, estimates are that the number of abortions is 30 to 40 per cent of the number of live births.

In many cases, the number of abortions appears to be directly connected with the availability of sex education, contraceptives and birth-control programs. For example, Japan's ratio - now about one abortion for every three births - is down sharply from figures 20 and 25 years ago, despite changes in customs and the casual ease with which abortions can be arranged.

In other places - Yugoslavia is perhaps the best example - religious and cultural traditions have the strongest impact. In Serbia, where the Orthodox Church is relatively less strict on sexual mores than either the Catholic Church or Islam, the average number of abortions per married woman is 1.78. "Every year in Belgrade" which is in Serbia "we kill the equivalent of the population of a small town - about 40,000," a Yugoslav doctor said.

In wealthier, Catholic Slovenia, it is 0.28, and in Moslem Kosovo it is 0.23, lowest in the country.

By contrast, laws regulating abortion seem to have little effect, other than channeling women to illegal abortionists. When Josef Stalin made abortions illegal in 1936, it produced only a short-term rise in the Soviet birthrate: when Nikita Khrushchev made them legal in 1955, there was no perceptible drop in the birthrate.

Prof. Dmitri Velentei of Moscow University argues that banning abortions is useless: "A woman who does not want to have a baby will not have it. Legal barriers have practically no effect anywhere in the world."

The French Movement for Family Planning says that France in general is even more hostile to contraception and sex education than to abortion. The organization's director, Simone Iff, says: "Contraception remains a privilege of wealth and is not widely practiced by the working class. A woman who demands contraception is asking for the right to make love when she wants. Her punishment is abortion. This is the Catholic mentality."

Iff's group, a privately funded organization that works closely with the Ministry of Health, estimates that 75 per cent of French women do not use contraceptives.

In Italy, where fewer than 5 per cent of women are thought to use any contraceptive method other than coitus interruptus, a study five years ago of more than 500 30-year-old married women in Rome showed two abortions for every two or three children.

A referendum on abortion is to be held next spring, unless an abortion law is passed before then, and it is widely expected that the result will be similar to the 1974 divorce referendum, when 60 per cent voted for its legalization. Meanwhile, illegal abortions and charter trips to London presumably will continue to be the main-stays.

England, with its relatively liberal laws that draw foreign women by the thousands - some 27,000 last year - presents an anomaly. Although there is reported to be wide public support for the present laws, anti-abortion sentiment is high in the House of Commons, and there is some expectation that the law may be made more restrictive.

Pro-abortion forces in Commons believe they have a chance to prevent the new restrictions from passing into law by bottling them up in committee, but the fact that they are trying to kill the bill rather than let it come to a vote shows how strong the anti-abortion side has become.

In Macho Spain, where widely available contraceptives are cutting down the number of abortions, King Juan Carlos is continuing the practice begun by Generalissimo Francisco France of awarding medals to parents of large families. The king has three children, and Franco had only one, a daughter.