A doctor testified yesterday that a federal abortion ban targets procedures intertwined with the most common methods of terminating pregnancies. Dr. Joel Howell, a medical historian at the University of Michigan, testified during a trial in U.S. District Court in Linconl, Neb., challenging the constitutionality of the federal ban. Other challenges are being heard this week in San Francisco and New York. The Partial-Birth Abortion Act, signed into law by President Bush last year, bars the procedure that medical organizations refer to as “intact dilation and extraction” — or D&X. During the procedure, generally performed in the second trimester, a fetus is partially delivered and its skull is punctured. But Howell said surgical procedures like those done in abortions evolve over the years and create variations of methods. “It is a very typical pattern of development,” he said. “Modifications develop of existing surgical procedures to make them safer.” Lawyers from the Center for Reproductive Rights, who filed the Lincoln lawsuit challenging the ban, contend that the federal law is vague and could be interpreted as covering more common, less controversial procedures, including “dilatation and evacuation.” Known as D&E, it is the most common method of second-trimester abortion. An estimated 140,000 D&Es take place in the United States annually. The ban has not been enforced, because judges in three cities agreed to hear evidence before deciding whether it violates the Constitution. The other challenges were filed by the National Abortion Federation and the Planned Parenthood Federation of America. The Lincoln challenge was filed on behalf of abortion provider Dr. LeRoy Carhart of Bellevue, and three other doctors. Carhart brought a challenge that eventually led the U.S. Supreme Court to overturning Nebraska’s partial-birth abortion ban in 2000. The high court said the Nebraska law and others like it were an “undue burden” on women’s rights. Supporters of the federal ban argue that Congress wrote its law to take into account the court’s objections to the Nebraska statute. U.S. District Judge Richard Kopf, who is presiding over the trial, also presided over Carhart’s challenge to the Nebraska ban. The federal law prohibits doctors from committing an “overt act” designed to kill a partially delivered fetus. The federal act carries a maximum two-year prison term for doctors convicted of performing the procedure. The issue is expected to reach the Supreme Court. Also party to the Lincoln case is Dr. Jill Vibhakar, who practices medicine at Emma Goldman Clinic for Women and at the University of Iowa College of Medicine Hospital in Iowa City, Iowa. Vibhakar testified Tuesday that the term “overt act” was vague in the law. Enforcing the ban might force her to quit doing abortions in the second trimester of pregnancy, Vibhakar said. It would force other doctors to inject drugs such as digoxin to induce fetal demise before a late D&E, after 20 weeks, she said. “I might not be willing to incorporate that into my practice,” she said. In issuing a temporary restraining order last year blocking enforcement of the federal ban, Kopf cited concerns that the law did not contain an exception for preserving the health of a woman seeking the abortion. Congress declared that “a partial birth abortion is never necessary to preserve the health of a woman” and is “outside the standard of medical care.” The American Medical Association does not encourage use of D&X, but says it should not be banned. The College of Obstetricians and Gynecologists says alternatives to D&X usually exist, but that in some circumstances, it may be the best procedure. An estimated 2,200 to 5,000 such abortions are performed annually in the United States out of 1.3 million total abortions. Also party to the lawsuit in Lincoln are Dr. William Fitzhugh of Richmond, Va., and Dr. William Knorr, medical director and co-owner of the Savannah Women’s Medical Clinic in Savannah, Ga.