Quote from Chapter 1:
“How did that happen?” I asked him.
He looked aside at me without turning his head and lifted his eyebrows. “Did no one ever have this talk with you?”
I scowled. “I mean, weren’t you careful?”
“Yes,” Thomas said. “And my kind are all but infertile to boot. Happened anyway.”
They didn't take that many precautions, if they had Justine wouldn't be pregnant.
In art as in real life, that doesn't always stop it from happening. If I remember correctly Justine has always had some emotional issues that the White Court thing actually helped. Anyway, it could be because she loves Thomas so much she wants to give him a child no matter the risks to her own health and the baby being born with a demon/parasite inside of it.
The text says they were careful. Justine is pregnant. I'll need a little more before I entertain the conclusion that they weren't careful.
If you use condoms perfectly every single time you have sex, they're 98% effective at preventing pregnancy. But people aren't perfect, so in real life condoms are about 85% effective — that means about 15 out of 100 people who use condoms as their only birth control method will get pregnant each year.
But no method or combination of methods is guaranteed to be 100 percent effective. The only guaranteed way to not get pregnant is by not having vaginal intercourse.
Planned Parenthood.
For perfect use of the male condom and pill, that’s 0.02 x 0.003 = 0.00006, or 0.006%. In other words, the combined method is over 99.99% effective when used perfectly.
https://www.mathscareers.org.uk/article/statistically-safe-sex/.
99.994% to be exact given their numbers. Now if they have "typical use" efficacy, the failure rate is 12%.
To figure out the chance of Thomas and Justine getting pregnant, we would need to know how much less fertile Thomas and Justine are compared with the average couple and how much more sex they have than the average couple. (Or just the yearly fertility rate compared to a human yearly fertility rate). We don't know these numbers, but I imagine they favor the propagation of an existing species. We could try to look to the scene in
Blood Rites where we see the mothers of Raith's children. The paintings fill up a library in a mansion starting in the 15 or 16 hundreds "steadily" progressing through fashions. None happening within "twenty or thirty years." Though we should note that there are only about 15 years between Thomas and Inari.
Then we have to take into account whatever the opposite of plot armor is into account. Once all that's taken into account, the chances of pregnancy, with perfect use of contraception, would be approaching 100%.
It's been two years and two months since
Ghost Story when Thomas started feeding again. Justine has "seven and a half months" of pregnancy left. I'm assuming Thomas is going off of a nine month pregnancy. Therefore Justine conceived two years and two weeks after feedings resumed.
All that considered, I'd say it was statistically unlikely that Justine would be pregnant, but probably not anywhere close to statistically impossible.
@g33k: I believe Raith has more than four daughters. It's just that we've only ever seen three on screen and identified as such at one time.
