he House of Delegates, plowing through a logjam of legislation to meet a mid-session deadline, today gave preliminary approval to a "natural death" bill that would give terminally ill people the right to order that their lives not be prolonged by artificial means.

But House members defeated a proposal to set up a state-run lottery in Virginia.

A voice-vote approval of the "natural death" measure came as a surprise, particularly after the House, in a move regarded as a defeat to antiabortion activists, deleted any reference to pregnant women. The Richmond Catholic Diocese had wanted language in the bill that would have barred pregnant women from the right to choose a natural death.

Women's groups, who had waged a furious lobbying campaign to extend the choice of "natural death" to pregnant women, were elated by today's vote. "This is a clear indication that prochoice people do express the opinion of the majority of the population," said Tonia Brown, director of the Virginia Beach based Organization to Keep Abortion Legal.

Nicholas Spinella, an attorney for the Richmond Diocese, said he was disappointed at the deletion of the pregnancy exemption, but that he expects the bill to win final House approval Monday.

"I think this will hurt its chances in the Senate," said Spinella, adding that he would seek to have the pregnancy exclusion restored there. "What the bill advocates now is an unnatural death, not a natural one."

Spinella, a member of the committee that helped draft the bill, said he was not withdrawing his support yet. "We'll just have to wait and see what happens in the Senate," he said.

The Richmond diocese had long opposed "death with dignity" legislation but reversed its position with the provision that the pregnancy clause be included. Support by the diocese was considered crucial to passage of the bill last week in committee.

Controversy over the bill has pitted Richmond's liberal Bishop Walter F. Sullivan against antiabortion activists and Northern Virginia's conservative Bishop Thomas J. Welsh, who say they fear the bill could lead to euthanasia.

Some Northern Virginia parish newsletters distributed at Mass today urged defeat of the bill, and several days ago Welsh sent House members, who must run for reelection this year, a letter opposing the bill.

"This bill fools a lot of people," said Geline B. Williams, director of the National Right to Life Committee, after today's vote. Williams likened the bill's potential impact to Nazi exterminations and said "this could be used against the handicapped and the minorities."

The bill's sponsor Del. Bernard S. Cohen, an Alexandria Democrat, denied that and said his proposal gives terminally ill people the right to choose not to prolong their lives artificially.

"It's a good bill, but right now it has a slight fever," said Cohen, referring to the controversy over deletion of the pregnancy clause. "We're going to give it a little chicken soup" by asking senior citizens groups to lobby for the measure in hopes of diffusing the pregnancy issue, he said. "This is a bill that most affects the elderly."

The lottery bill, which would have let voters decide the issue at the polls next November, was defeated 58 to 41 after opponents attacked lotteries as corrupting schemes that entice poor people to part with their money.

"I am very much opposed to it," said Del. William Wilson (D-Covington). "In Virginia, we have always had a reputation for clean, good government. Once you start down this road, I see no way you can logically say no to parimutual betting."

The specter of race track betting, roundly rejected by Virginia voters in 1977, did little to win support for the lottery measure in the House where delegates, up for reelection this fall, have little desire to see their campaigns clouded by a gambling proposal.

Still, the delegates rejected an earlier amendment that would have postponed the referendum on the lottery referendum until 1985, a nonelection year.

The lottery bill, reported from committee to the full House for the first time this year, was the first of several controversial measures expected to be voted on tonight by the House of Delegates. The deadline for sending House bills to the Senate is Monday night and to meet it, House committees had to work through the weekend.

The House today also approved a bill that would increase by five feet the length of trucks permitted on state roads. The extension of truck lengths, sought by industry lobbyists, went beyond a federal mandate to increase truck sizes on interstate highways.

But the first emotional debate of the day came on the lottery bill, which Del. Ralph L. Axselle called "one of those litmus tests--like collective bargaining or right to work."

A lottery, said Del. Henry W. Maxwell (D-Newport News), would encourage poor people "to reach for this pie in the sky. People will spend everything they have."

Pending approval by the voters next fall, the bill would have created a five-member state lottery commission that would be allowed to start operations in April 1984.

Estimates of revenues from a lottery varied, but some put it as high as $200 million. In hopes of persuading his colleagues, Del. William O'Brien (D-Virginia Beach), sponsor of the bill, noted that Maryland last year raised $175 million through its lottery and that the District of Columbia hopes to collect $30 million a year.