[Spoilers!] First chapter of PT

[didymos]

Also, there's Felicia from Ghost Story.  Don't know whose child she is, but she's clearly from the Raith side of things.

[Arjan]

There are all those nobles in the deeps in white night. About a third of them were Raiths and most of them did not live in the Raith mansions but were guests. There were more lesser vampires not invited. We have only seen the tip of the iceberg.

[Mira]

There are all those nobles in the deeps in white night. About a third of them were Raiths and most of them did not live in the Raith mansions but were guests. There were more lesser vampires not invited. We have only seen the tip of the iceberg.

But still tells you next to nothing...  The Red Court Vamps numbered in the thousands, maybe more because they created new members via infection..  From your evidence the White Court Vamps may number in the hundreds or fewer, which considering their long life spans speaks with a very low reproductive rate..  Listen to Thomas, their general fertility rate is very low, otherwise why would he think he was more than likely sterile?  There is a 50/50 chance things won't go well when the mother get's pregnant because the embryo Hunger demon feeds off the mother..   Thomas is the son of Lord Raith which might increase his chances of not being sterile in spite of him thinking he was, so they used birth control.. Perhaps not with the care they should have because Justine still got pregnant.

[Arjan]

Or his demon played a trick. It could be that it wanted to procreate.

[Mira]

Or his demon played a trick. It could be that it wanted to procreate.

Perhaps, or because he is the son of Lord Raith, or and I wouldn't be surprised if it is brought into
it at some point, true love.  Or back to my original point, it has something to do with Lord Raith wanting to kill off his sons, they can make babies like he can, that makes them a threat.  What I am getting at is I doubt that Jim would toss this in simply for melodramatic effect.   It might even take a few books, but I think it will be significant somewhere down the road..  Or here is a wild thought, from the trailer we know that Thomas is in significant trouble, is he injured enough to die?  Will he be executed or killed?  What is going to happen to Justine?  If she dies, who is going to raise the kid? Custody battle between Harry and Lara?  Just some wild thoughts in my self isolation...

[Arjan]

Perhaps, or because he is the son of Lord Raith, or and I wouldn't be surprised if it is brought into
it at some point, true love.  Or back to my original point, it has something to do with Lord Raith wanting to kill off his sons, they can make babies like he can, that makes them a threat.  What I am getting at is I doubt that Jim would toss this in simply for melodramatic effect.   It might even take a few books, but I think it will be significant somewhere down the road..  Or here is a wild thought, from the trailer we know that Thomas is in significant trouble, is he injured enough to die?  Will he be executed or killed?  What is going to happen to Justine?  If she dies, who is going to raise the kid? Custody battle between Harry and Lara?  Just some wild thoughts in my self isolation...

Thomas story is not finished yet. We first will get some dramatic stuff about their mother.

So here is my theory:

I read nothing dramatic in it. Of course the white court is nearly infertile otherwise we would be drowning in them. The demon is the big difference between the white court and normal humans so the demon must make them infertile.

For the demon too a child is a big investment in the future. I think it invests part if its life force, its spiritual power in the new child. That is not something lightly done so I think a white court vampire only procreates when the demon agrees to it in some level. Knowing how Thomas demon thinks about Justine this is a no brainer. The demon wanted a child and had enough influence to subvert all precautions.

[Mira]

Thomas story is not finished yet. We first will get some dramatic stuff about their mother.

Very true,  we do know a couple of things, Justine suffered from mental illness, being fed upon
has kept that in check, but I cannot remember if it cured her or not.  We also know she was willing to sacrifice her life to bring back Thomas when he was so severely hurt back in Blood Rites, and Thomas willing to jeopardize his full recovery by not feeding upon her until she died.  I still think "true love" will be a factor, as in possibly because Justine and Thomas have true love, their child was conceived in true love, not only will the demon not be able to feed on her, it will be burnt out trying.  Justine should be protected by the true love she feels for Thomas. Thus for the first time a child of a White Court Vampire will be born without the Hunger demon, truly breaking the cycle. Then again, Justine had sex with a girl friend to wreck her protection so she and Thomas could have sex. However a baby conceived in true love instead of lust might be different.

[didymos]

Very true,  we do know a couple of things, Justine suffered from mental illness, being fed upon
has kept that in check, but I cannot remember if it cured her or not. 

She started taking meds when she started working for Lara:

“It doesn’t matter right now,” Justine said. “I’m better.”
“You aren’t crazy, are you?” I demanded.
“You nearly scratched my eyes out that one time.”
She shook her head with a frustrated little motion. “Medication. It isn’t . . . Look, I’m all right for now. I need you to listen to me.”

Butcher, Jim. White Night (The Dresden Files, Book 9) . Penguin Publishing Group. Kindle Edition.

She may have stopped taking it though when she and Thomas started in again.

[Bad Alias]

why would he think he was more than likely sterile?

Because he didn't think he was more than likely sterile.

Then again, Justine had sex with a girl friend to wreck her protection so she and Thomas could have sex.

The trailer implies that she is protected again because they are wearing gloves. Does that mean the baby's demon can't feed? If so, does that mean it will wither and die?

[Mira]

Because he didn't think he was more than likely sterile.
The trailer implies that she is protected again because they are wearing gloves. Does that mean the baby's demon can't feed? If so, does that mean it will wither and die?

   There is a contradiction there because why else would he say he was more than likely sterile, unless he really thought it?  What underscores that actually is the botched job on the birth control.  I am not saying that birth control cannot fail, it can, and does on occasion.  However if you think you are sterile you less likely to carefully follow all the instructions as you should perhaps. 

I didn't notice her wearing gloves, will have to go back and look.  Obviously she wasn't protected when she got pregnant, but getting pregnant from an act of true love verses lust may have restore her protection.

She started taking meds when she started working for Lara:

Yes, but I believe she had been taking meds all along but they weren't helping as they should.  The act Thomas feeding drained off her excess emotions and cured her severe mood swings if I remember correctly from Storm Front or one of the other early books.

[didymos]

   There is a contradiction there because why else would he say he was more than likely sterile, unless he really thought it? 

He never said that. Again, here's the quote:

“Yes,” Thomas said. “And my kind are all but infertile to boot. Happened anyway.”

Yes, but I believe she had been taking meds all along but they weren't helping as they should.  The act Thomas feeding drained off her excess emotions and cured her severe mood swings if I remember correctly from Storm Front or one of the other early books.

It was Grave Peril where we meet her.  And she said she wasn't taking meds back then:

“Yes. Yes, Thomas. He makes it quieter. Inside me, there’s so much trying to get out, like at the hospital. Control, they said. I don’t have the kind of control other people have. It’s hormones, but the drugs only made me sick. He doesn’t, though. Only a little tired.”

Grave Peril (The Dresden Files, Book 3) (p. 384). Penguin Publishing Group. Kindle Edition.

Apparently, Lara got her better ones.

[morriswalters]

I will pledge some token amount if Jim will promise to take a class on reproductive biology.  If he wants to say that Whites have a low reproductive  rate he should just say so.  Carry on.

[g33k]

...  If he wants to say that Whites have a low reproductive  rate he should just say so ...

Ummm.
He did?

... my kind are all but infertile to boot. Happened anyway.

I mean, it's in-character stuff, so Thomas may have been lied-to, or be lying to Harry, or other sort of misinformation.

If it had been WoJ'ed (in an AMA or 'Con panel) or something, I guess it'd be "more reliable"?
 

[Yuillegan]

Does that mean the baby's demon can't feed? If so, does that mean it will wither and die?

Why can't the baby feed like a regular human baby? White Court Vampires are essentially mortal until they come of age (presumably 18, but I can't remember if that was explicitly stated) and feed, which I imagine summons the phage part of themselves that attaches itself to them. I suspect that this also quite probably occurs during the first time the WCV loses it's virginity, and knowing Jim this would only count if it was penetrative vaginal intercourse. I wonder how this accounts for underage sex and/or sexual abuse? Or gay vampires for that matter (assuming such a thing exists - it more than likely should with sex-vampires but who knows in the Dresden Files).

I also think everyone is getting too hung up on Thomas' (Jim's) choice of phrase. Little character intention 101: the line is less about the words used, and more about the thought behind it. The intention is clear i.e. that WCV can have babies BUT mostly do not because of biological and/or supernatural factors. Whether Thomas is telling the truth or is simply misinformed is an entirely different argument - and impossible to answer without more information.

[Bad Alias]

Why can't the baby feed like a regular human baby?

Because it doesn't?

Except that the baby’s Hunger will draw life energy from Justine. She’s going to be fed upon continuously for the next seven and a half months.