Last August Aden Mariano, a Somali citizen, left Washington with his 5-year-old son Koshin and returned to Africa. Though he was under a District Court order not to keep Koshin out of the United States for more than 60 days, he has not yet returned.

For Jacqueline Thompson, Mariano's American ex-wife and Koshin's mother, the thought that he may never return is almost more than she can bear.

"There are some days, I think I will see my son again. There are some days I think that it will be many years before I see him again. But I don't think my son will ever forget me," said Thompson, 31, a District resident and medical secretary at George Washington University Hospital.

Although a U.S. court has found her ex-husband in contempt and issued a warrant for his arrest, Thompson has discovered, as have numerous other American parents once involved in an international marriage, that U.S. court orders often have little practical effect in bringing home an abducted child taken abroad by a foreign spouse.

According to Patricia Hoff, head of the American Bar Association's "Child Custody Clearinghouse and Information Center," Thompson's situation "is far from an isolated case." Since January, 1979, the State Department has been asked to help locate children abducted to foreign countries in 677 cases. About half of those (337) were taken to West European countries. The second highest number (174) went to Latin and Central American nations.

"In a typical situation at the ABA center the mother will call from a midwestern city and she has married a man, typically from the Middle East, and she says, 'He's gone with the kids, what can I do?' " Hoff said.

Thompson, a 1973 graduate of Wellesley, met Mariano when he was a student at Northeastern University and she was working at Boston City Hospital in 1975. They fell in love, married the next year and Koshin was born in 1977. But then the marriage broke up and a bitter custody battle began first in Massachusetts courts and then here. For a while, Mariano worked as a part-time employe of the Somali embassy here, according to a transcript of the court hearings.

Last April, D.C. Superior Court judge Margaret A. Haywood gave Mariano temporary custody of his child. She also gave him permission to take Koshin back to Africa to see his relatives, but said he could be gone for only 60 days.

Mariano took Koshin to Zambia to visit his grandfather, Michael T. Mariano, the Somali Ambasssdor to Zambia. He later took Koshin to Djibouti, a small country next to Somalia on the East Coast of Africa, where they are now living, according to information Thompson received from the State Department.

In January a District Court judge ruled Mariano in contempt of court and issued a bench warrant for his arrest. But unless Mariano voluntarily returns to the United States, this order has little practical effect in reuniting Thompson with her son. A hearing is scheduled for April to determine permanent custody of the child, Thompson said.

In such situations the State Department can try to locate the child in a foreign country, provide information about the local courts and names of local lawyers, but little else, a State Department official said. It also can deny a passport to a child if the American parent presents a court order showing that the child is not allowed to travel outside the United States without her permission. But it is easy enough for the foreign spouse to get around this by applying for a foreign passport for the child.

Thompson has spent hours writing letters for help to U.S. officials. Two of District Del. Walter E. Fauntroy's staff members visited Somali ambassador Mohamud Haji Nur on her behalf.

"The meeting was very productive. The ambassador understands the humanitarian imperatives of the situation," said Fauntroy aide Steve Horblitt. "But the problem is that there is not a lot we can do from this end. We just don't have jurisdiction. All we can try is to exercise persuasion. We've had similar cases in the past and it's just very difficult."

Thompson's appeals for help to the Somali embassy have produced no results, she said.

Of course, the shoe can be on the other foot, and often is. "It cuts both ways. If you were a French woman wouldn't you feel bad if your husband took your children to the U.S.?" a State Department official said.

The State Department has no record of how many times foreign parents have sought assistance in getting children returned from Americans in the United States.

Lawyers say American parents often are under the misconception that they will get a better deal in U.S. courts, and with that in mind, they defy foreign court custody orders and bring their children here.

But "a case will not be decided in favor of an American solely on citizenship," said Hoff. And in a sample survey of binational child custody disputes, Hoff found that U.S. courts often ruled in favor of the foreign parent and against the American parent if it was shown the foreign court proceedings were fair and proper.

Forty-eight states have already adopted the Uniform Child Custody Jurisdiction Act, which urges U.S. state courts to recognize and enforce foreign court orders that meet certain standards, Hoff said. The D.C. City Council has also adopted the act.

However, this is not always reciprocal and there is no guarantee that a foreign court will honor an American state court order, Hoff said.

In order to change this, about 30 countries (most of them in Westewrn Europe, plus the United States) have drawn up an international agreement on child abduction. This agreement would set up a special agency in each signatory country to help parents whose children have been abducted. It also would make it easier for American parents to get the foreign courts' help in recovering their children if they are in one of the signatory countries.

The international agreement will be sent to Congress for U.S. ratification this summer.

Meanwhile, Hoff advises that one of the greatest preventions against getting into such predicaments is "prudence, before one gets into life-long commitments, one of which is children."