Just spoke to a biologist and she has the answer.
First, yes I'm an idiot the pig things is not what I said, you where right here, sorry.
Now I asked this biologist this question and the first thing she asked was "Could it be that Delenn (I gave her the names, she didn’t watch B5) has some Human DNA in her?
Obviously she does, being Valan descendent.
Now, according to her two races CAN reproduce even if they DON'T have the same number of chromosomes as long as the chromosomes can align. This is why mules are born out of two creatures of different species, this new creature (the mule) can not reproduce but it can exist (this leads me to think that we don't know whether David can have an offspring or not so this can be the answer – David is a "mule").
Now to the more cool aspect of her answer:
My friend said that if Delenn has some Human DNA in her the chrysalis could have been some kind of a stimulator which, like in human teenagers, awakened the needed RNA sections which in turn made the changes in Delenn.
These changes DID NOT made Delenn human, it did however made her compatible to human GENOM making her able to carry the new offspring.
This, by the way, doe's NOT make her a hybrid at all, she is still Minbar only one with specific encoding of a human.
This happens in nature when Wolves and Dogs mate, their offspring is capable of bringing new offspring out of wolves, dogs OR other of their own kind.
We must remember, she said, that the DNA is the whole potential, and in any DNA segment we can find all the information needed to create a full human BUT still we have fingers and toes and eyes, all created from the SAME DNA but each part different, this is made by the RNA.
I love this; it makes sense and shows us that B5 IS totally based on REAL science FACTS.
Also I must add that I love this forum, I found only one like this one where I can have an intelligent discussions with other people..
Hope this clear up everything to all of us