Mary Duncan was 17 when she went missing in 1976, telling her family she was going to meet a friend.
Her step-father, Norman Duncan, 73, was jailed in 2016 for abusing four girls during the 1960s and 1970s.
His victims were aged between eight and 15 years old when they were attacked between 1968 and 1976, and Duncan was jailed for five years for the crimes.
Mary left her home in Third Avenue, Bonhill, West Dunbartonshire, on March 19, 1976, after telling her family she was going to meet a friend, but she never returned.
The teenager had become pregnant at the age of 15 and gave birth to a baby girl, Laura Duncan, on February 17, 1975.
She did not take her daughter with her when she disappeared, and baby Laura died of natural causes on October 25, 1976.
Cops have been scouring the home where Duncan was listed as living on court papers from 2016.
The suburban house, 128 Ladyton in Bonhill, West Dunbartonshire, has been a hive of police activity for more than 24 hours.
Uniformed officers were stationed outside the drab front garden, while forensics teams and detectives went in and out.
One neighbour, who spoke on condition of anonymity, said: “Since 6am police have been coming in and out all day.
“Forensics have left now and CID have been in and out most of the day as well.
“They’ve been in the back garden of the property.
“Forensics were taking pictures of the property, back and front.”
For 43 years, Mary’s sisters, Debbie, Marion and Mandy, have questioned what happened to their sibling.
Last year, in July, they made a public appeal to find out what happened to Mary.
At the time, Detective Superintendent Calum Young, said: “At the age of 17, Mary was a devoted mother to a baby girl called Laura.
“Her family say Mary absolutely adored her daughter and that her disappearance, and leaving Laura behind, was completely out of character.
“Mary left home with no money and she has never claimed benefits, paid tax or national insurance.
“Her family strongly doubt that she would have had the means or life skills to start a new life and live independently.
“Whilst there is no evidence to suggest that Mary came to any harm, due to the fact that she has not been seen or heard from in more than 41 years, we can’t rule this out.
“Mary’s family were left completely devastated by her disappearance, a pain which lives with them to this day, and it is vital that we get to the bottom of what happened to their sister and provide them with some closure.
“I would ask anyone who knew Mary or her family in the years before her disappearance to please get in touch to help us piece together the details of her life around the time she went missing.
“No matter how insignificant you think your help may be, let us be the judge of that, because even the slightest detail could be important.
“Even if you spoke to the police back in 1976, there’s been a huge passage of time and we would like to speak to you again.
“Some of our enquiries have focused on the Vale of Leven Hospital and I would appeal to anyone who worked there in 1976 to come forward as they may be able to assist with our investigation.
“I believe the answer to what happened to Mary lies within the local community and it is very possible that someone does have information and is concerned about coming forward now because they should have contacted the police 41 years ago.
“If anyone is in this situation, please don’t be concerned about that.
“The important thing is that you come forward now and tell us what you know.
“Mary’s family have waited long enough for answers.”
A spokesman for Police Scotland said: “Police are currently searching an address in Ladyton, Alexandria, as part of an ongoing investigation.”