A Palestinian fertility doctor claimed Wednesday that he has used prisoners' sperm smuggled out of Israeli jails to help their wives have babies, and that five women have become pregnant so far.

Despite unlikely odds and difficult conditions, a fertility expert said the claims could be plausible.

There are about 4,500 Palestinians in Israeli jails, serving sentences for offenses ranging from stone throwing to killing Israeli civilians.

Most women seeking to become pregnant have husbands who were convicted of taking part in deadly militant attacks and are serving lengthy sentences. These prisoners are barred from having conjugal visits.

"We women are growing old, and our chances of having babies in the future is diminishing," said Rimah Silawi, 38, who said she is one month pregnant after undergoing IVF treatments that used her imprisoned husband's sperm. Her husband, Osama, is serving multiple life sentences for killing an Israeli and three Palestinians said to be collaborators with the Israeli military in the West Bank town of Jenin 22 years ago.

Dr. Salim Abu Khaizaran of the Razan Center for IVF in the West Bank city of Nablus said he has gathered 40 samples, and that 22 prisoners' wives have undergone IVF treatment. Five have been successful, including one woman who delivered her baby earlier this year. He said the success rate was low because of the difficulty in transporting the samples successfully. The Western rate of IVF success is about 25 percent in ideal hospital conditions.

Abu Khaizaran said he gives the service for free in solidarity with the prisoners.

"The wives of prisoners are suffering. They feel they are lonely because their husbands are behind bars, some for the rest of their lives, and they are eager to have babies that can make a difference in their lives," Abu Khaizaran said.

Relatives refused to say how the sperm is smuggled out, fearing the information would help Israeli authorities to prevent further attempts. They said the samples were usually carried out in eye droppers.

While he did not provide firm proof of paternity, he said his treatments received the consent of both sides of the families.

One prisoner's wife said her husband hid his sample in clothing that he was allowed to give to a visitor. She the sample was rushed to the clinic, where it was frozen. She said the trip took four hours. She spoke on condition of anonymity because she feared her husband would be punished.

Israel's prison authority said Abu-Khaizaran's claims were unlikely. "We place doubt in the ability of the security prisoners to accomplish such a task, considering the existing conditions and the tools at their disposal," said spokeswoman Sivan Weizman.

An independent fertility expert said the efforts were plausible.

Dr. Jennifer Kulp Makarov of the Maimonides Medical Center in New York said sperm could be viable for several hours outside the body, and IVF treatments only need "a few viable sperm" for success. The average sample has 40 million sperm, she said.

"It's possible," Kulp Makarov said. "After a few hours, you would still have a few million."

Palestinian lawyers who visit prisoners said it would be difficult, but not impossible, to smuggle sperm out of Israeli prisons. Although prisoners are separated from their visitors by a glass barrier, young children are allowed to hug their fathers and could potentially carry items out. Sympathetic prison guards might also be willing to look the other way.

"If you can sneak in a phone to a prison, then you can sneak sperm out," said lawyer Mahmoud Hassan.