What was going on when I was born?

Former President Reynaldo Bignone was arrested tonight in an investigation into the disappearance of two army conscripts, both Communists, in 1976. The arrest order was announced by Judge Carlos Oliveri after General Bignone left a court where he had testified for nearly five hours on the disappearances of two Communists. The general was already being held under what is known as ''preventive prison,'' the equivalent of indictment without bail, for investigation of criminal charges of abuse of authority, covering up an illegality and illegal detention.

A QUESTION often asked, especially by women, is, ''How much milk should I drink every day to get enough calcium?'' The answer, which often elicits a gasp, is you should consume as much calcium as there is in five glasses of milk. Few Americans, at least few adult Americans, come anywhere near that level of calcium intake. And the statistics on osteoporosis and broken bones show that we are paying a high price for our neglect of this vital nutrient. In just a few years osteoporosis, a disease once unheard of by most women, has become a common concern. And well it should be, among young as well as older women. For this debilitating bone disorder, which is virtually epidemic among American women past the age of 60, has its roots in young adulthood. Prevention should start as early as the teen years. Depending upon how long they live, up to 40 percent of American women develop osteoporosis, the first sign of which is usually a broken bone or collapsed vertebra. While men are not immune to this problem, for various reasons - especially the hormonal changes that accompany menopause - women are much more likely to develop it. After menopause, the average American woman loses an inch and a half in height each decade as a result of vertebral collapse. Far more serious, millions of fractures and tens of thousands of deaths occur annually because of osteoporosis.

ZITACUARO, Mexico IF Diana Kennedy feels blessed in her new home here, about 100 miles west of Mexico City, it is small wonder. It is a magnificent hideaway in the center of a mountain-ringed forest with tall poinsettias, bougainvilleas, fruit-bearing passionflowers and a thicket of wildflowers. The house is made of adobe bricks, a windmill produces electricity, the heat is solar and the water for cooking and drinking collected from rainfall. When I arrived there one recent morning Mrs. Kennedy was just stepping out of her pickup truck. ''I've just delivered the pig to the vet,'' she said. ''I had to deliver the milk to the market, and while I was there an old man said, 'Won't you buy my duck because I need the money?' So I did. My gardener just told me that one of the cows is pregnant, and I have more guests coming to dinner.''

Senator John Tower, chairman of the Armed Services Committee, who returned Monday night from a weeklong trip to the Middle East, said today that a withdrawal of American troops from Lebanon now would be ''disastrous.'' In addition, Mr. Tower, Republican of Texas, said at a news conference that moving the Marine contingent away from Beirut International Airport, where it has repeatedly been under fire, would not increase its security. In Lebanon, meanwhile, officials said that a plan to reduce hostilities by separating the warring factions was being delayed by the demands of groups allied with Syria. (Page 4.)

Washington and the Vatican established full diplomatic relations for the first time in 117 years. The action was described by spokesmen for the Reagan Administration as aimed at improving communications at a time when Pope John Paul II has become increasingly involved in international affairs. (Page A1, Column 6.) Many Protestant groups, some Jewish groups and some civil liberties organizations criticized the re-establishment of full diplomatic ties between the United States and the Vatican. (A4:4-6.)

The European Common Market is preparing to curb imports from the United States of basic chemicals and sporting equipment in retaliation against Reagan Administration restraints, announced last July, on imports of specialty steel from Europe, a top American trade official said today. The official, Robert E. Lighthizer, the deputy United States trade representative, told a news briefing that the Common Market had submitted a preliminary list of products on which it plans to raise tariffs or impose quotas. He also raised the possibility of American countermeasures. Under international trading rules, the submission of a list is a prerequisite to retaliation by countries that feel they have been wronged by other countries' trade measures.

For years public school systems in the South have been rated among the poorest in the country in terms of state financial support and pupil performance. Now, more than in any other region, political leaders in the South are pursuing innovative programs, tied to increases in state taxes and aimed at reversing a legacy of poorly financed schools, low teacher salaries and high student dropout rates. ''In terms of need, there's a greater imperative for reform in the South than in any other part of the country,'' said Gov. Richard W. Riley, Democrat of South Carolina, who has asked the state Legislature in Columbia to raise the state sales tax by a cent to help finance a $210 million education package. Comprehensive education reform programs tied to increases in the state sales tax are pending before the state Legislatures this winter in South Carolina and in Tennessee. Similar programs have already been enacted in Mississippi, Florida and Arkansas.

Former State Senator Vander L. Beatty of Brooklyn, who was convicted last month of state charges involving election fraud, was accused by Federal authorities yesterday of stealing more than $200,000 from a neighborhood rehabilitation program. f1013 The United States Attorney's office in Brooklyn made public an indictment charging Mr. Beatty with racketeering, mail fraud and seeking to obstruct Federal investigators by giving them ''disguised and misleading'' samples of his handwriting. Conviction on the Federal racketeering charge, the most serious count, would carry a sentence of up to 20 years in prison. The false-handwriting charge recalls a charge that state authorities made against Mr. Beatty last summer when they said he had given them fraudulent samples of his handwriting during their own investigations of his activities.

A Federal advisory committee today gave President Reagan four broad recommendations to alleviate hunger in America at only slight additional cost to the Government. In its final report, the 13-member panel said, ''Numerous witnesses have testified to us in the most forceful Excerpts from report, page 10. terms about the existence of widespread and growing hunger in this country.'' But the panel concluded, ''General claims of widespread hunger can neither be positively refuted nor definitively proved.'' On Monday, after a detailed summary of the report was made public, antipoverty groups, religious organizations, civil rights groups and some Democratic members of Congress criticized the tone of the report and its recommendations, saying they underestimated the problem.

In 1970 Harvey Tauman took over a successful family-owned dental laboratory from his father and sold most of its equipment to concentrate on selling what he thought would be a revolutionary new material to make dentures. Thirteen years later Dento-Med Industries, with only four employees, had yet to market the material. But the Miami Beach concern was the biggest hit in the 1983 stock market, dwarfing companies far larger by scoring the biggest percentage gain, nearly 25-fold. Most analysts have not heard of Dento-Med. In fact, many say they cannot explain why a small company, which lost $184,310 in its latest nine months, could make such a roar.

WEDNESDAY, JANUARY 11, 1984 International A fire has jeopardized shipments of natural gas through the new pipeline from Siberia, according to reports circulating in Moscow. The fire is said to have destroyed imported electronic equipment. The reports appear to undermine Soviet claims that the pipeline has already begun to deliver gas to France. But spokesmen in the U.S. for two companies associated with the pipeline said they had heard nothing of any such fire. (Page A1.) The Common Market is preparing to curb imports from the U.S. of basic chemicals and sporting equipment, a top American trade official announced. He said the move would be in retaliation for the Reagan Administration's restrictions on imports of specialty steel from Europe. If the retaliation occurs, experts suggested, it could touch off a serious trans-Atlantic trade conflict. (D1.)

Because of an editing error, an article on the Washington Talk page yesterday, about telecommunciations, misidentified Ellis Woodward, a former press advance official in the Carter White House. He is an aide to Representative Timothy E. Wirth, Democrat of Colorado.