An Arlington woman was arrested and charged with first-degree murder yesterday after her husband told police that his wife had smothered their 6-month-old daughter in her crib eight years ago.

The woman, Sharon Lynn Latimer, 31, of 4718 N. 20th Pl., was released on $5,000 bond set by Prince George's District Court. Her attorney said she would plead innocent.

Prince George's police said Latimer was accused of putting a plastic bag over her sleeping daughter Kathryn's face and suffocating the baby. The incident allegedly took place about midnight, Feb. 2, 1971, at 6504 Perry St., Hyattsville, where the family then lived, police said.

During the summer of 1978, police said, Mrs. Latimer told her husband, Thomas R. Latimer, that she had committed the offense. Police said the couple separated sometime after her husband learned of the incident.

On Aug. 1 of this year the husband, who had gone to Florida with the couple's other two children, told Largo, Fla., police the story his wife had told him about the death of their daughter, police here said.

After an investigation by Prince George's County police, Mrs. Latimer was charged early yesterday.

Family members who did not want to be identified said it has always been assumed that the baby died of some unexplained illness such as "crib death."

They recalled that Thomas Latimer was on a business trip at the time. The couple had another child, who was 3 years old at the time, and has had another baby since.

Officials in the state's attorney's office said that although the incident took place more than eight years ago there is no statute of limitations in a murder case. Prosecutors also said they were looking into why the husband failed to reveal what he knew about the baby's death until a year after he learned it.

At her bond hearing yesterday, Mrs. Latimer appeared in the uniform and sneakers she was issued by the county detention center where she had been held since her arrest. Several family members were present and when she entered the courtroom, she saw them, rolled her eyes sadly and then looked toward the judge.