Citing fears about I.V.F., Tammy Duckworth urges Senate not to confirm Judge Barrett.

Senator Tammy Duckworth, Democrat of Illinois, raised concerns about Judge Amy Coney Barrett’s views on in vitro fertilization on Friday and urged the Senate not to confirm her.

Ms. Duckworth’s two daughters were conceived using in vitro fertilization, or I.V.F., and her youngest became the first infant to appear on the Senate floor in 2018.

In her letter, Ms. Duckworth said she felt “dread and anguish” when she learned that Judge Barrett “likely doesn’t believe my little Maile and my growing Abigail should have ever been born in the first place.”

Judge Barrett, President Trump’s Supreme Court nominee, signed a newspaper ad in 2006 that was placed by an anti-abortion group in Indiana called St. Joseph County Right to Life. The group has made statements opposing in vitro fertilization, a process that often involves discarding fertilized embryos.

Judd Deere, a spokesman for the White House, did not immediately respond to a question about Judge Barrett’s views on I.V.F. but pointed to statements she had made about her commitment to the rule of law.

“As Judge Barrett said on the day she was nominated,” Mr. Deere wrote in an email Friday, “‘A judge must apply the law as written. Judges are not policymakers, and they must be resolute in setting aside any policy views they might hold.’ ”

The 2006 newspaper ad, which had hundreds of signatories including Judge Barrett, did not mention in vitro fertilization. It said that the signatories would “defend the right to life from fertilization to natural death.”

In her letter, Ms. Duckworth wrote that “St. Joseph County Right to Life is an organization whose views are considered radical even within the larger anti-choice movement, in part due to its stated belief that a critical step of the in vitro fertilization process that gave me my children is equivalent to manslaughter.”

Jackie Appleman, the executive director of the group, which is now called Right to Life Michiana, declined to comment when reached by phone on Friday. On Thursday, The Guardian reported Ms. Appleman as saying that she opposed the discarding of embryos during the in vitro fertilization process and likened it to abortion.

“We support the criminalization of the doctors who perform abortions,” Ms. Appleman was reported as saying. “At this point we are not supportive of criminalizing the women.”

Ms. Duckworth urged her colleagues in the Senate not to confirm Judge Barrett’s nomination. “I fear that, if confirmed to the nation’s highest court, Judge Barrett would be unable to resist the temptation of overturning decades of judicial precedent in an effort to force every American family to adhere to her individual moral code,” she added.