WALNUT CREEK, Calif. -- The Danville couple who were eagerly looking forward to becoming parents again after losing their two children to a hit-and-run driver have lost their unborn twins in a pregnancy complication.

Carmen Pack's pregnancy was terminated Friday as infections linked to tears in the amniotic sacs of the twin male fetuses she was carrying began to threaten her life, her husband said.

At 20 weeks gestation, the twins were too young to survive a premature delivery.

"There was no other choice," said Bob Pack. "It's heartbreaking."

The Packs' two children, Troy, 10, and Alana, 7, were killed in 2003 by a driver who crashed into them on a sidewalk, then fled the scene. The driver, a nanny who was convicted of second-degree murder this month in the deaths, had four earlier DUI convictions. Testimony suggested she was under the influence of drugs, alcohol or both when she struck the young brother and sister.

The Packs battled to bring the nanny to justice and lobbied for state laws that now make it harder for people to expunge such crimes and regain their licenses.

The couple also successfully lobbied for a humanitarian visitor's visa for Carmen Pack's Peruvian niece so the young woman could donate eggs to help the couple get pregnant.

Carmen Pack, 44, was recovering Saturday at John Muir Hospital in Walnut Creek, where she has been since Tuesday. She began experiencing complications on Mother's Day.

"Life can throw you a curveball that is unbelievable at times," Bob Pack said earlier this week when the couple learned of the problems.

The couple wants to try again to have children, said Pack. They have six embryos left from the in vitro fertilization process responsible for the twins.

Pack said the fetuses will be buried at Queen of Heaven Cemetery in Lafayette next to Troy and Alana.