Mr. Basso, whose broadtail designs cost $7,000 to $45,000, said no client had ever challenged him about the source of his skins. "Women who want something beautiful are only interested in the final product," he said. "She's buying fashion. She's not going into Prada and asking, 'Where did this come from?' It's like when somebody goes and buys a diamond. They're not asking what mine it came from either."

Albert Kriemler, the designer of Akris, said he would never use broadtail from a lamb fetus. The astrakhan in his designs comes from naturally born lambs raised in China and bought at fur auctions in Moscow and Oslo, which the fur industry accepts as providing the best and most reputable pelts. The appeal of high-quality astrakhan is its relative scarcity, Mr. Kriemler said, noting that although one of his designs was featured in the Bergdorf catalog, he does not expect to sell more than 25 pieces.

"As with all luxury items, the more exclusive it is the more desirable it becomes for the couture designer customer we deal with," he said.

Several designers would not directly answer whether the furs they call astrakhan come from fetal lambs, but a representative for Dolce & Gabbana confirmed it uses both types in its fall collection. A spokeswoman for Marc Jacobs, whose fall collection includes an astrakhan coat trimmed with ruffles, carried by Barneys New York, said she could not determine whether it was broadtail. Prada, which has frequently identified its product as broadtail, did not respond to numerous inquiries. A spokeswoman for Mr. Armani said the fur described as astrakhan in his fall collection is not fetal lamb.

Despite the ubiquity of astrakhan in designer collections, the trend has so far not stirred much opposition from animal-rights groups, which have conducted vociferous anti-fur campaigns. Dan Mathews, the vice president of People for the Ethical Treatment of Animals, said that astrakhan made of newborn and fetal lambs is used more than designers acknowledge, but he said the issue is not at the top of his organization's agenda. It has focused attention in recent months on the Australian wool trade practice of mulesing, removing a strip of skin from the rump of sheep to reduce susceptibility to fly larvae, and the treatment of animals raised for Kentucky Fried Chicken, which, Mr. Mathews said, "face a lifetime of mutilation and misery."

Michael Markarian, the executive vice president of the Humane Society of the United States, which also opposes the use of fur in fashion, said he was concerned by the use of furs that do not resemble animal skins, which he said was a way to appeal to a younger customer who might not know the origins of the material.