What was going on when I was born?

The Reagan Administration promised King Hussein of Jordan today that if he agreed to join the Middle East peace negotiations, the United States would seek to bring about a halt in the building of Israeli settlements in the West Bank. The statement was issued by the State Department amid uncertainty and concern in Washington over King Hussein's talks with Yasir Arafat, chairman of the Palestine Liberation Organization. There are reports that Mr. Arafat has been unable to secure wide support in the P.L.O. to give King Hussein authority to negotiate with Israel on behalf of Palestinians living in the Israeli-occupied West Bank and Gaza. Palestinian officials said today that Mr. Arafat chose not to return to Amman from Kuwait to complete his talks with King Hussein because of substantial differences that remained between the two men. (Page 4.)

The agricultural miracle that permits this small town in Arkansas County to call itself the rice capital of the world is about to begin again with spring planting. But the chemicals that make the miracle possible may also pose a health threat to the region's residents, according to doctors and scientists. The so-called phenoxy herbicides 2,4,5-T, silvex and 2,4-D, used here to combat aquatic weeds that can clog rice fields, are contaminated by dioxins, one of which is the most toxic compound synthesized by man. Dioxins have been shown to cause cancer in animals, although their effects on humans are still being studied. The Environmental Protection Agency banned the herbicides 2,4,5-T and silvex for most uses in 1979. However, an exception was made for rice paddies and rangelands, even though the agency said the pesiticides posed ''risks which are greater than the social, economic and environmental benefits.''

By 11 o'clock Thursday morning Graciela Oster, eight months pregnant, feared that the moment was at hand, just as the flood waters were rising. So she and her family headed for Southern Baptist Hospital in New Orleans, 20 miles from their home in Chalmette. When they reached the hospital, it was surrounded by rushing rivers usually known by such names as Napoleon Avenue and Clara Street. The Osters called to two men in a boat nearby. ''My sister-in-law told me to turn sideways to show them I was pregnant,'' Mrs. Oster recalled from her bed today.

Economic hardships, outside political pressures and a campaign by anti-Sandinist guerrillas in northern and central Nicaragua appear to have widened a gap between the Government and important segments of the middle class. ''There is no longer any middle ground in our revolution,'' Leticia Herrera, national director of the Sandinist Defense Committees, told a wildly cheering crowd of several hundred impoverished Nicaraguans who gathered at a public meeting here a few days ago. ''Now is the time to close ranks against the enemies of the people,'' Miss Herrera declared. The enemies, she said, are not only the anti-Sandinist insurgents but also ''the speculators, the people who spread rumors on buses and in markets, and the taxi drivers who force their passengers to listen to criticisms of the revolution.'' Although the insurgents have not managed to seize even the smallest village or achieve any other substantial military success, they have prompted the Sandinist Government to begin a new wave of attacks against its domestic critics, aggravating the political polarization.

State officials said yesterday that New York City would have a budget surplus of between $158 million and $300 million this fiscal year. Mayor Koch said he would be able to use some of the money to avoid many of the employee reductions and tax increases he had planned for the fiscal year 1984. ''The money is there and we're going to spend it, and we're not going to spend it on a party,'' Mr. Koch said at a City Hall news conference. He declined to say specifically how city services and agencies would benefit, or which taxes he would drop from the long list he has proposed.

President Reagan, seeking to recover from a severe setback in the Senate on his military budget, authorized staff aides today to try to salvage a compromise with the Budget Committee, White House officials reported. The aim is to get more than the 5 percent military spending increase that the committee approved Thursday, the officials said. The Senate Republican leadership had been pleading for days before the vote that the President accept a compromise to salvage a greater proportion of the 10 percent increase that he has insisted is necessary. In the committee vote, a bipartisan majority rejected Mr. Reagan's plan by a vote of 17 to 4 and approved a military spending increase that was only half the 10 percent that Mr. Reagan had called for. The percentages are on top of increases intended to make up for the effects of expected inflation.

For the thousands of people accustomed to eating, sleeping and peddling their wares along this capital's alleys and roads, Boulevard Jean Jacques Dessalines was once a choice spot. The boulevard, which is Port-au-Prince's main street, runs past the busiest stores and the central market buildings, so the peddler who had his own little patch on its cluttered sidewalks regarded himself as being in the hub of things. But the street life of Port-au-Prince and its unspoken, intricate rules have been disrupted as a result of Pope John Paul II's brief visit here in March. Because the Pope's motorcade was to pass along the boulevard, municipal workers trucked some 5,000 vendors, beggars and other street people out of town in the days before he arrived.

South Africa's Parliament has enacted legislation that recognizes for the first time the status of conscientious objectors to military service. Although the new legislation is not cast in racial terms, it would now apply only to whites, for only whites are required to serve in the military. But it is widely anticipated that the draft will eventually be extended to two nonwhite minorities, the mixed-race coloreds and the Indians, if Prime Minister P.W. Botha's plan to give them a form of franchise on racially segregated voters' rolls is finally adopted. The bill, which is due to be signed into law any day by the ceremonial head of state, provides harsh penalties for those who refuse to serve for moral or political reasons that fall outside its narrow definition of conscientious objection. Essentially, to achieve the status a draftee has to contend that he objects to all war on religious grounds and would refuse to bear arms for any army anywhere.

The Soviet Union brought out a 95-page booklet today as part of its campaign against the deployment of new American medium-range missiles in Europe. The book was announced at a news conference for foreign reporters at which 13 ranking officials were present. The booklet, titled ''How to Avert the Threat to Europe,'' is largely an updating of a publication issued in 1981. The fanfare with which it was issued today, however, reflected the intensity of Moscow's quickening campaign against the deployment of the new American missiles, scheduled to begin by the end of the year unless an agreement is reached with the Soviet Union.

Son Sann, the former Cambodian Prime Minister, charged today that Vietnamese troops had massacred ''several hundreds'' of civilians, including women and children, in overrunning a rebel camp Monday on the Cambodian side of the border with Thailand. Speaking before a crowd of more than 5,000 Cambodian refugees at Thailand's Khao-I-Dang holding center, 20 miles north of here, Mr. Son Sann said he had seen ''the mutilated survivors of this deliberate massacre'' who had managed to flee the camp at O Smach and reach a hospital in Surin Province on the Thai side of the border. O Smach, the former military headquarters of forces loyal to Prince Nordom Sihanouk, the former Cambodian chief of state, is 75 miles northeast of Aranyaprathet. Mr. Son Sann charged that Vietnamese troops at O Smach had herded civilians into a trench and then ''threw hand grenades in there and finished them off with bayonets.''

The Fort Worth Chamber Orchestra began a 21-day tour of China today, a day after the Government canceled 19 sports and cultural exchange events to protest Washington's decision to grant political asylum to a Chinese tennis star. The Fort Worth group's tour was not canceled because it was considered an unofficial visit. But the executive director of the American group said the orchestra would not play joint concerts with Chinese musicians. The director, Ann Koonsman, said the Chinese told the Americans that plans for two joint concerts were inappropriate in the current political climate. The Fort Worth orchestra will perform alone on those two occasions.

The State Department announced today that the United States would start an immediate airlift of ground-to-air missiles, howitzers and other weapons to Thailand to help the Government reinforce its border against any intrusion by Vietnamese troops from Cambodia. The State Department spokesman, John Hughes, said that in speeding deliveries of American weapons previously ordered by Thailand, the United States was responding to an appeal by Thailand ''for help against the Vietnamese border attacks.'' Two days ago Thailand accused Vietnam of trying to provoke a showdown with Thai forces through incursions across the border and said the Vietnamese would have to accept the consequences of any Thai retaliation.