A father repeatedly raped his two daughters during a campaign of abuse which resulted in 19 pregnancies, a court has heard.
The 56-year-old, from Sheffield, had earlier pleaded guilty to 25 rapes and four indecent assaults.
The attacks led to nine children being born, two of whom died. The other 10 pregnancies were miscarried or aborted.
Sheffield Crown Court was told he "took pleasure" in knowing the harm he was doing to his daughters.
The court heard that the sexual abuse started when the two sisters reached the age of eight but that they only realised the other was being abused when they became pregnant some years later.
The court heard that on a number of occasions doctors advised the women to stop having children by the same father.
On one occasion a doctor asked one of the women whether her father was also the father of her child. She flatly denied the accusation.
Nicholas Campbell QC said: "The defendant played Russian roulette as to whether there would be complications in the pregnancies and with the health of his daughters."
When either one of his victims tried to end the sexual abuse, he threatened to kill them and their children
Nicholas Campbell QC
Their father, who cannot be named for legal reasons, threatened them with a "real hiding" if they refused to have sex with him.
Mr Campbell said: "All the defendant's children spoke of his domination over their family life. He was tall and strongly built."
Mr Campbell said the father "liked to think that he was the hard man".
He added: "All the family were frightened of him. When they heard his car pulling up outside the house, the children and their mother ran to their respective rooms.
"His younger daughter told of the frightening habit her father had of putting her head next to the flames of their gas fire and that when she struggled to get away on certain occasions she burnt her eyes.
"The sisters recall that they were kept from school when they bore physical injuries. The defendant also ensured that his family were kept isolated and that there were very few visitors to the home.
"Rather than having babysitters, the children recall being locked in their rooms when their mother and father went out."
On one occasion, the women called Childline and asked for a guarantee that they could keep their children, but when one was not offered they ended the call.
Mr Campbell said: "When either one of his victims tried to end the sexual abuse, he threatened to kill them and their children, and when they threatened to tell police, he said they would not be believed.
"He said that if they went public then the children would be taken away from them.
"All the time, when the sisters were challenged about the paternity of their children, they would cover it up.
"They started taking the pill. He said they should not be taking it and, just as they felt unable to avoid his sexual abuse, they obeyed.
"They spoke of his pleasure at fathering their children whilst at the same time they had fears for the welfare of these children and how they would cope."