Charlie Sheen and wife Brooke Mueller at 60th Annual Primetime Emmy Awards held at Nokia Theatre - Arrivals. Los Angeles, California - 21.09.08

After fathering three daughters - Sam and Lola with ex-wife Denise Richards and Cassandra with ex-girlfriend Paula Profit - actor Sheen is desperate for a son.

According to the National Enquirer, the pair paid to have the star's X and Y sperm separated, and Mueller was inseminated with just the Y sperm, giving their chances of having a son an 80 per cent boost.

And a source close to the couple claims it worked.

Sheen himself hinted that Mueller is carrying a boy, when he announced her pregnancy in August (08), by saying, "Brooke informed me two days ago that very soon we'd be producing our own version of (his hit U.S. TV show) Two-and-a-Half Men."

But Sheen insists he's not bothered if the baby is a boy or a girl - as long as it's healthy.

In a recent interview, the actor said, "Ultimately, we just want a healthy child. We know everyone says that, but it's the truth."

Source: WENN