Good news for lesbians who want to have biological children related to both parents: a new stem-cell technique could allow scientists to convert female cells into sperm. Use that sperm to fertilize an egg, and voila: children with two female biological parents.

In unpublished work reported by New Scientist and the Telegraph, British scientists at the University of Newcastle coaxed female embryonic stem cells to develop into primitive sperm cells. Next, the researchers, led by stem-cell biologist Karim Nayernia, plan to create sperm cells from female bone marrow, making the procedure more practical. They haven’t yet made the primitive sperm undergo the final cell division that generates the correct amount of genetic material for fertilization, a process known as meiosis.

Scientists have been skeptical that sperm can be produced from female cells, which lack a Y chromosome and thus whichever Y-linked genes are crucial to sperm production.

According to the Telegraph:

Dr Robin Lovell-Badge, a stem cell and sex determination expert at the National Institute for Medical Research, Mill Hill, London, doubts it will work: “The presence of two X chromosomes is incompatible with this. Moreover they need genes from the Y chromosome to go through meiosis. So they are at least double-damned.”

Nayernia’s team has had success generating sperm from male stem cells. Last year, the researchers made primitive sperm from stem cells collected from adult men. And in a 2006 proof of principle experiment, Nayernia used “sperm derived from male embryonic stem cells to fertilize mice to produce seven pups, six of which lived to adulthood, though the survivors did suffer problems,” according to the Telegraph.