Many of those surveyed said they would consider using their eggs to become single mothers in their 40s, local media reported on Saturday. Usually, most women have eggs frozen to preserve their fertility while they undergo treatment for cancer. But now more and more career women choose to use the service for social reasons.

Doctors at Mount Sinai School of Medicine in New York interviewed 20 women with an average age of 38.6 who had chosen to have their eggs frozen. Half said they felt pressured by their biological clocks; 65 percent said they only recently became aware of egg freezing technology.

All the women had bachelor's degrees and three quarters had masters or professional qualifications.

Alan Copperman, who led the study, said many saw the technology as a means of delaying having children until they were in a fulfilling relationship. "Cryo-preservation meant the freedom to wait, and to not settle for a mate because they were in a rush to conceive," he said.

The interviews revealed that 40 percent were "definitely willing" to have their eggs fertilized with donor sperm and become single parents, with 40 percent undecided about conceiving without a partner. The other 20 percent ruled out being a single mother.

Researchers reported the findings to the American Society for Reproductive Medicine conference in New Orleans.