The One With The Donor - S9-E22
Question: Chandler and Monica are told that aside from adoption there are two ways for them to have a baby, either using a surrogate or a sperm donor. But if Monica would be able to carry the child of the sperm donor, and a surrogate would be able to carry Monica and Chandler's child, wouldn't Monica be able to carry Chandler's child using the same process as used with a surrogate?
Answer: If (just) surrogacy is an option, that means that IVF using Chandler's sperm and Monica's egg must be possible. If (just) a sperm donor is an option, that means that Monica must be capable of carrying a child. So, yes, with the situation as presented by the doctor, Monica could have carried Chandler's child after IVF. The only rational explanation would be that the doctor misspoke, and should have said that they would need both a sperm donor -and- a surrogate (because Chandler's sperm couldn't be used in IVF and Monica couldn't carry a child at all). This was simply a mistake made by the writers.